Tuflow - User contributions [en]

3xxx TUFLOW Messages

2026-07-30T21:22:51Z

Emilie Nielsen:

The 3xxx TUFLOW messages refer to issues that occur in the HPC solver. These messages are often included in .tlf files along with 2XXX error messages:

<pre> NoXY: ERROR 2447 - Sending HT hydrograph to HPC. HPC ERROR Code (see hpc.tlf) = 3022 </pre>
Or included at the end of .hpc.tlf files:
<pre> ERROR 3022: Number of Boundary Level Graphs exceeded. Maximum is 253. </pre>

 
Click on number to follow link to TUFLOW message description, grey numbers are reserved and do not yet have messages assigned, and red numbers have been allocated to new messages.

See also:
* [[0xxx TUFLOW Messages]]
* [[1xxx TUFLOW Messages]]
* [[2xxx TUFLOW Messages]]
* [[4xxx TUFLOW Messages]]
* [[5xxx TUFLOW Messages]]
* [[6xxx TUFLOW Messages]]

{| Border ="1" cellpadding="8" style="text-align:center"
|3000 || [[TUFLOW Message 3001|3001 ]] || [[TUFLOW Message 3002|3002 ]] || [[TUFLOW Message 3003|3003 ]] || [[TUFLOW Message 3004|3004 ]] || [[TUFLOW Message 3005|3005 ]] || [[TUFLOW Message 3006|3006 ]] || [[TUFLOW Message 3007|3007 ]] || [[TUFLOW Message 3008|3008 ]] || [[TUFLOW Message 3009|3009 ]] || [[TUFLOW Message 3010|3010 ]] || [[TUFLOW Message 3011|3011 ]] || [[TUFLOW Message 3012|3012 ]] || [[TUFLOW Message 3013|3013 ]] || [[TUFLOW Message 3014|3014 ]] || [[TUFLOW Message 3015|3015 ]] || [[TUFLOW Message 3016|3016 ]] || [[TUFLOW Message 3017|3017 ]] || [[TUFLOW Message 3018|3018 ]] || [[TUFLOW Message 3019|3019 ]]
|-
|[[TUFLOW Message 3020|3020 ]] || [[TUFLOW Message 3021|3021 ]] || [[TUFLOW Message 3022|3022 ]] || [[TUFLOW Message 3023|3023 ]] || [[TUFLOW Message 3024|3024 ]] || [[TUFLOW Message 3025|3025 ]] || [[TUFLOW Message 3026|3026 ]] || [[TUFLOW Message 3027|3027 ]] || [[TUFLOW Message 3028|3028 ]] || [[TUFLOW Message 3029|3029 ]] || [[TUFLOW Message 3030|3030 ]] || [[TUFLOW Message 3031|3031 ]] || [[TUFLOW Message 3032|3032 ]] || [[TUFLOW Message 3033|3033 ]] || [[TUFLOW Message 3034|3034 ]] || [[TUFLOW Message 3035|3035 ]] || [[TUFLOW Message 3036|3036 ]] || [[TUFLOW Message 3037|3037 ]] || [[TUFLOW Message 3038|3038 ]] || [[TUFLOW Message 3039|3039 ]]
|-
|[[TUFLOW Message 3040|3040 ]] || [[TUFLOW Message 3041|3041 ]] || [[TUFLOW Message 3042|3042 ]] || [[TUFLOW Message 3043|3043 ]] || [[TUFLOW Message 3044|3044 ]] || [[TUFLOW Message 3045|3045 ]] || [[TUFLOW Message 3046|3046 ]] || [[TUFLOW Message 3047|3047 ]] || [[TUFLOW Message 3048|3048 ]] || [[TUFLOW Message 3049|3049 ]] || [[TUFLOW Message 3050|3050 ]] || 3051 || 3052 || 3053 || 3054 || 3055 || [[TUFLOW Message 3056|3056 ]] || 3057 || 3058 || 3059
|-
|[[TUFLOW Message 3100|3100 ]] || [[TUFLOW Message 3101|3101 ]] || 3102 ||3103|| 3104 || 3105 || 3106 || 3107 || 3108 || 3109 || 3110 || 3111 || 3112 || 3113 || 3114 || 3115 || 3116 || 3117 || 3118 || 3119
|-
|3180 || 3181 || 3182 ||3183|| 3184 || 3185 || 3186 || 3187 || 3188 || 3189 || 3190 || 3191 || 3192 || 3193 || 3194 || 3195 || 3196 || 3197 || 3198 || [[TUFLOW Message 3199|3199 ]]
|-
|[[TUFLOW Message 3200|3200 ]] || [[TUFLOW Message 3201|3201 ]] || 3202 ||3203|| 3204 || 3205 || 3206 || 3207 || 3208 || 3209 || 3210 || 3211 || 3212 || 3213 || 3214 || 3215 || 3216 || 3217 || 3218 || 3219
|-
|[[TUFLOW Message 3500|3500 ]] || [[TUFLOW Message 3501|3501 ]] || [[TUFLOW Message 3502|3502 ]] ||[[TUFLOW Message 3503|3503 ]]|| [[TUFLOW Message 3504|3504 ]] || [[TUFLOW Message 3505|3505 ]] || [[TUFLOW Message 3506|3506 ]] || [[TUFLOW Message 3507|3507 ]] || [[TUFLOW Message 3508|3508 ]] || [[TUFLOW Message 3509|3509 ]] || [[TUFLOW Message 3510|3510 ]] || [[TUFLOW Message 3511|3511 ]] || [[TUFLOW Message 3512|3512 ]] || [[TUFLOW Message 3513|3513 ]] || [[TUFLOW Message 3514|3514 ]] || [[TUFLOW Message 3515|3515 ]] || [[TUFLOW Message 3516|3516 ]] || [[TUFLOW Message 3517|3517 ]] || [[TUFLOW Message 3518|3518 ]] || [[TUFLOW Message 3519|3519 ]]
|-
|[[TUFLOW Message 3520|3520 ]] || [[TUFLOW Message 3521|3521 ]] || [[TUFLOW Message 3522|3522 ]] ||[[TUFLOW Message 3523|3523 ]] || [[TUFLOW Message 3524|3524 ]] || [[TUFLOW Message 3525|3525 ]] || [[TUFLOW Message 3526|3526 ]] || [[TUFLOW Message 3527|3527 ]] || [[TUFLOW Message 3528|3528 ]] || [[TUFLOW Message 3529|3529 ]] || [[TUFLOW Message 3530|3530 ]] || [[TUFLOW Message 3531|3531 ]] || [[TUFLOW Message 3532|3532 ]] || [[TUFLOW Message 3533|3533 ]] || [[TUFLOW Message 3534|3534 ]] || [[TUFLOW Message 3535|3535 ]] || [[TUFLOW Message 3536|3536 ]] || [[TUFLOW Message 3537|3537 ]] || [[TUFLOW Message 3538|3538 ]] || [[TUFLOW Message 3539|3539 ]]
|-
|[[TUFLOW Message 3540|3540 ]] || [[TUFLOW Message 3541|3541 ]] || 3542 || [[TUFLOW Message 3543|3543 ]] || [[TUFLOW Message 3544|3544 ]] || [[TUFLOW Message 3545|3545 ]] || [[TUFLOW Message 3546|3546 ]] || [[TUFLOW Message 3547|3547 ]] || [[TUFLOW Message 3548|3548 ]] || [[TUFLOW Message 3549|3549 ]] || [[TUFLOW Message 3550|3550 ]] || [[TUFLOW Message 3551|3551 ]] || [[TUFLOW Message 3552|3552 ]] || [[TUFLOW Message 3553|3553 ]] || [[TUFLOW Message 3554|3554 ]] || 3555 || 3556 || [[TUFLOW Message 3557|3557 ]] || 3558 || 3559
|-
|[[TUFLOW Message 3560|3560 ]] || [[TUFLOW Message 3704|3704 ]] || 3962 || 3963 || 3964 || 3965 || 3966 || 3967 || 3968 || 3969 || 3970 || 3971 || 3972 || 3973 || 3974 || 3975 || 3976 || 3977 || 3978 || 3979
|-
|3980 || 3981 || 3982 || 3983 || 3984 || 3985 || 3986 || 3987 || 3988 || 3989 || 3990 || [[TUFLOW Message 3991|3991 ]] || 3992 || 3993 || 3994 || 3995 || 3996 || 3997 || 3998 || [[TUFLOW Message 3999|3999 ]]
|}
 
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2xxx TUFLOW Messages

2026-07-30T03:16:21Z

Emilie Nielsen:

The 2xxx TUFLOW messages refer to issues that occur neither in the 2D model. Click on number to follow link to TUFLOW message description, grey numbers are reserved and do not yet have messages assigned, and red numbers have been allocated to new messages.

See also:
* [[0xxx TUFLOW Messages]]
* [[1xxx TUFLOW Messages]]
* [[3xxx TUFLOW Messages]]
* [[4xxx TUFLOW Messages]]
* [[5xxx TUFLOW Messages]]
* [[6xxx TUFLOW Messages]]

{| Border ="1" cellpadding="8" style="text-align:center"
|2000 || [[TUFLOW Message 2001|2001 ]] || [[TUFLOW Message 2002|2002 ]] || [[TUFLOW Message 2003|2003 ]] || [[TUFLOW Message 2004|2004 ]] || [[TUFLOW Message 2005|2005 ]] || [[TUFLOW Message 2006|2006 ]] || [[TUFLOW Message 2007|2007 ]] || [[TUFLOW Message 2008|2008 ]] || [[TUFLOW Message 2009|2009 ]] || [[TUFLOW Message 2010|2010 ]] || [[TUFLOW Message 2011|2011 ]] || [[TUFLOW Message 2012|2012 ]] || [[TUFLOW Message 2013|2013 ]] || [[TUFLOW Message 2014|2014 ]] || [[TUFLOW Message 2015|2015 ]] || [[TUFLOW Message 2016|2016 ]] || [[TUFLOW Message 2017|2017 ]] || [[TUFLOW Message 2018|2018 ]] || [[TUFLOW Message 2019|2019 ]]
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|[[TUFLOW Message 2020|2020 ]] || [[TUFLOW Message 2021|2021 ]] || [[TUFLOW Message 2022|2022 ]] || [[TUFLOW Message 2023|2023 ]] || [[TUFLOW Message 2024|2024 ]] || [[TUFLOW Message 2025|2025 ]] || [[TUFLOW Message 2026|2026 ]] || [[TUFLOW Message 2027|2027 ]] || [[TUFLOW Message 2028|2028 ]] || [[TUFLOW Message 2029|2029 ]] || [[TUFLOW Message 2030|2030 ]] || [[TUFLOW Message 2031|2031 ]] || [[TUFLOW Message 2032|2032 ]] || [[TUFLOW Message 2033|2033 ]] || [[TUFLOW Message 2034|2034 ]] || [[TUFLOW Message 2035|2035 ]] || [[TUFLOW Message 2036|2036 ]] || [[TUFLOW Message 2037|2037 ]] || [[TUFLOW Message 2038|2038 ]] || [[TUFLOW Message 2039|2039 ]]
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|[[TUFLOW Message 2040|2040 ]] || [[TUFLOW Message 2041|2041 ]] || [[TUFLOW Message 2042|2042 ]] || [[TUFLOW Message 2043|2043 ]] || [[TUFLOW Message 2044|2044 ]] || [[TUFLOW Message 2045|2045 ]] || [[TUFLOW Message 2046|2046 ]] || [[TUFLOW Message 2047|2047 ]] || [[TUFLOW Message 2048|2048 ]] || [[TUFLOW Message 2049|2049 ]] || [[TUFLOW Message 2050|2050 ]] || [[TUFLOW Message 2051|2051 ]] || [[TUFLOW Message 2052|2052 ]] || [[TUFLOW Message 2053|2053 ]] || [[TUFLOW Message 2054|2054 ]] || [[TUFLOW Message 2055|2055 ]] || [[TUFLOW Message 2056|2056 ]] || [[TUFLOW Message 2057|2057 ]] || [[TUFLOW Message 2058|2058 ]] || [[TUFLOW Message 2059|2059 ]]
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|[[TUFLOW Message 2060|2060 ]] || [[TUFLOW Message 2061|2061 ]] || [[TUFLOW Message 2062|2062 ]] || [[TUFLOW Message 2063|2063 ]] || [[TUFLOW Message 2064|2064 ]] || [[TUFLOW Message 2065|2065 ]] || [[TUFLOW Message 2066|2066 ]] || [[TUFLOW Message 2067|2067 ]] || [[TUFLOW Message 2068|2068 ]] || [[TUFLOW Message 2069|2069 ]] || [[TUFLOW Message 2070|2070 ]] || [[TUFLOW Message 2071|2071 ]] || [[TUFLOW Message 2072|2072 ]] || [[TUFLOW Message 2073|2073 ]] || [[TUFLOW Message 2074|2074 ]] || [[TUFLOW Message 2075|2075 ]] || [[TUFLOW Message 2076|2076 ]] || [[TUFLOW Message 2077|2077 ]] || [[TUFLOW Message 2078|2078 ]] || [[TUFLOW Message 2079|2079 ]]
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|[[TUFLOW Message 2080|2080 ]] || [[TUFLOW Message 2081|2081 ]] || [[TUFLOW Message 2082|2082 ]] || [[TUFLOW Message 2083|2083 ]] || [[TUFLOW Message 2084|2084 ]] || [[TUFLOW Message 2085|2085 ]] || [[TUFLOW Message 2086|2086 ]] || [[TUFLOW Message 2087|2087 ]] || [[TUFLOW Message 2088|2088 ]] || [[TUFLOW Message 2089|2089 ]] || [[TUFLOW Message 2090|2090 ]] || [[TUFLOW Message 2091|2091 ]] || [[TUFLOW Message 2092|2092 ]] || [[TUFLOW Message 2093|2093 ]] || [[TUFLOW Message 2094|2094 ]] || [[TUFLOW Message 2095|2095 ]] || [[TUFLOW Message 2096|2096 ]] || [[TUFLOW Message 2097|2097 ]] || [[TUFLOW Message 2098|2098 ]] || [[TUFLOW Message 2099|2099 ]]
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|[[TUFLOW Message 2100|2100 ]] || [[TUFLOW Message 2101|2101 ]] || [[TUFLOW Message 2102|2102 ]] || [[TUFLOW Message 2103|2103 ]] || [[TUFLOW Message 2104|2104 ]] || [[TUFLOW Message 2105|2105 ]] || [[TUFLOW Message 2106|2106 ]] || [[TUFLOW Message 2107|2107 ]] || [[TUFLOW Message 2108|2108 ]] || [[TUFLOW Message 2109|2109 ]] || [[TUFLOW Message 2110|2110 ]] || [[TUFLOW Message 2111|2111 ]] || [[TUFLOW Message 2112|2112 ]] || [[TUFLOW Message 2113|2113 ]] || [[TUFLOW Message 2114|2114 ]] || [[TUFLOW Message 2115|2115 ]] || [[TUFLOW Message 2116|2116 ]] || [[TUFLOW Message 2117|2117 ]] || [[TUFLOW Message 2118|2118 ]] || [[TUFLOW Message 2119|2119 ]]
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|[[TUFLOW Message 2120|2120 ]] || [[TUFLOW Message 2121|2121 ]] || [[TUFLOW Message 2122|2122 ]] || [[TUFLOW Message 2123|2123 ]] || [[TUFLOW Message 2124|2124 ]] || [[TUFLOW Message 2125|2125 ]] || [[TUFLOW Message 2126|2126 ]] || [[TUFLOW Message 2127|2127 ]] || [[TUFLOW Message 2128|2128 ]] || [[TUFLOW Message 2129|2129 ]] || [[TUFLOW Message 2130|2130 ]] || [[TUFLOW Message 2131|2131 ]] || [[TUFLOW Message 2132|2132 ]] || [[TUFLOW Message 2133|2133 ]] || [[TUFLOW Message 2134|2134 ]] || [[TUFLOW Message 2135|2135 ]] || [[TUFLOW Message 2136|2136 ]] || [[TUFLOW Message 2137|2137 ]] || [[TUFLOW Message 2138|2138 ]] || [[TUFLOW Message 2139|2139 ]]
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|[[TUFLOW Message 2140|2140 ]] || [[TUFLOW Message 2141|2141 ]] || [[TUFLOW Message 2142|2142 ]] || [[TUFLOW Message 2143|2143 ]] || [[TUFLOW Message 2144|2144 ]] || [[TUFLOW Message 2145|2145 ]] || [[TUFLOW Message 2146|2146 ]] || [[TUFLOW Message 2147|2147 ]] || [[TUFLOW Message 2148|2148 ]] || [[TUFLOW Message 2149|2149 ]] || [[TUFLOW Message 2150|2150 ]] || [[TUFLOW Message 2151|2151 ]] || [[TUFLOW Message 2152|2152 ]] || [[TUFLOW Message 2153|2153 ]] || [[TUFLOW Message 2154|2154 ]] || [[TUFLOW Message 2155|2155 ]] || [[TUFLOW Message 2156|2156 ]] || [[TUFLOW Message 2157|2157 ]] || [[TUFLOW Message 2158|2158 ]] || [[TUFLOW Message 2159|2159 ]]
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|[[TUFLOW Message 2160|2160 ]] || [[TUFLOW Message 2161|2161 ]] || [[TUFLOW Message 2162|2162 ]] || [[TUFLOW Message 2163|2163 ]] || [[TUFLOW Message 2164|2164 ]] || [[TUFLOW Message 2165|2165 ]] || [[TUFLOW Message 2166|2166 ]] || [[TUFLOW Message 2167|2167 ]] || [[TUFLOW Message 2168|2168 ]] || [[TUFLOW Message 2169|2169 ]] || [[TUFLOW Message 2170|2170 ]] || [[TUFLOW Message 2171|2171 ]] || [[TUFLOW Message 2172|2172 ]] || [[TUFLOW Message 2173|2173 ]] || [[TUFLOW Message 2174|2174 ]] || [[TUFLOW Message 2175|2175 ]] || [[TUFLOW Message 2176|2176 ]] || [[TUFLOW Message 2177|2177 ]] || [[TUFLOW Message 2178|2178 ]] || [[TUFLOW Message 2179|2179 ]]
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|[[TUFLOW Message 2180|2180 ]] || [[TUFLOW Message 2181|2181 ]] || [[TUFLOW Message 2182|2182 ]] || [[TUFLOW Message 2183|2183 ]] || [[TUFLOW Message 2184|2184 ]] || [[TUFLOW Message 2185|2185 ]] || [[TUFLOW Message 2186|2186 ]] || [[TUFLOW Message 2187|2187 ]] || [[TUFLOW Message 2188|2188 ]] || [[TUFLOW Message 2189|2189 ]] || [[TUFLOW Message 2190|2190 ]] || [[TUFLOW Message 2191|2191 ]] || [[TUFLOW Message 2192|2192 ]] || [[TUFLOW Message 2193|2193 ]] || [[TUFLOW Message 2194|2194 ]] || [[TUFLOW Message 2195|2195 ]] || [[TUFLOW Message 2196|2196 ]] || [[TUFLOW Message 2197|2197 ]] || [[TUFLOW Message 2198|2198 ]] || [[TUFLOW Message 2199|2199 ]]
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|[[TUFLOW Message 2200|2200 ]] || [[TUFLOW Message 2201|2201 ]] || [[TUFLOW Message 2202|2202 ]] || [[TUFLOW Message 2203|2203 ]] || [[TUFLOW_Message_2204| 2204]] || [[TUFLOW Message 2205|2205 ]] || [[TUFLOW Message 2206|2206 ]] || 2207 || [[TUFLOW Message 2208|2208 ]] || 2209 || [[TUFLOW Message 2210|2210 ]] || [[TUFLOW Message 2211|2211 ]] || [[TUFLOW Message 2212|2212 ]] || [[TUFLOW Message 2213|2213 ]] || [[TUFLOW Message 2214|2214 ]] || [[TUFLOW Message 2215|2215 ]] || [[TUFLOW Message 2216|2216 ]] || [[TUFLOW Message 2217|2217 ]] || [[TUFLOW Message 2218|2218 ]] || [[TUFLOW Message 2219|2219 ]]
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|[[TUFLOW Message 2220|2220 ]] || [[TUFLOW Message 2221|2221 ]] || [[TUFLOW Message 2222|2222 ]] || [[TUFLOW Message 2223|2223 ]] || [[TUFLOW Message 2224|2224 ]] || [[TUFLOW Message 2225|2225 ]] || [[TUFLOW Message 2226|2226 ]] || [[TUFLOW Message 2227|2227 ]] || [[TUFLOW Message 2228|2228 ]] || [[TUFLOW Message 2229|2229 ]] || [[TUFLOW Message 2230|2230 ]] || [[TUFLOW Message 2231|2231 ]] || [[TUFLOW Message 2232|2232 ]] || [[TUFLOW Message 2233|2233 ]] || [[TUFLOW Message 2234|2234 ]] || [[TUFLOW Message 2235|2235 ]] || [[TUFLOW Message 2236|2236 ]] || [[TUFLOW Message 2237|2237 ]] || [[TUFLOW Message 2238|2238 ]] || [[TUFLOW Message 2239|2239 ]]
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|[[TUFLOW Message 2240|2240 ]] || [[TUFLOW Message 2241|2241 ]] || [[TUFLOW Message 2242|2242 ]] || 2243 || [[TUFLOW Message 2244|2244 ]] || 2245 || [[TUFLOW Message 2246|2246 ]] || [[TUFLOW Message 2247|2247 ]] || [[TUFLOW Message 2248|2248 ]] || 2249 || 2250 || 2251 || 2252 || 2253 || 2254 || 2255 || 2256 || 2257 || 2258 || 2259
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|2300 || 2301 || [[TUFLOW Message 2302|2302 ]] || 2303 || [[TUFLOW Message 2304|2304 ]] || [[TUFLOW Message 2305|2305 ]] || [[TUFLOW Message 2306|2306 ]] || 2307 || [[TUFLOW Message 2308|2308 ]] || [[TUFLOW Message 2309|2309 ]] || [[TUFLOW Message 2310|2310 ]] || [[TUFLOW Message 2311|2311 ]] || 2312 || [[TUFLOW Message 2313|2313 ]] || [[TUFLOW Message 2314|2314 ]] || [[TUFLOW Message 2315|2315 ]]|| [[TUFLOW Message 2316|2316 ]] || [[TUFLOW Message 2317|2317 ]] || 2318 || [[TUFLOW Message 2319|2319 ]]
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|[[TUFLOW Message 2320|2320 ]] || [[TUFLOW Message 2321|2321 ]] || 2322 || [[TUFLOW Message 2323|2323 ]] || 2324 || 2325 || 2326 || 2327 || 2328 || [[TUFLOW Message 2329|2329 ]] || [[TUFLOW Message 2330|2330 ]] || [[TUFLOW Message 2331|2331 ]] || 2332 || [[TUFLOW Message 2333|2333 ]] || [[TUFLOW Message 2334|2334 ]] || [[TUFLOW Message 2335|2335 ]] || [[TUFLOW Message 2336|2336 ]] || [[TUFLOW Message 2337|2337]] || [[TUFLOW Message 2338|2338]] || 2339
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|[[TUFLOW Message 2340|2340 ]] || 2341 || 2342 || [[TUFLOW Message 2343|2343 ]] || 2344 || 2345 || 2346 || [[TUFLOW Message 2347|2347 ]] || [[TUFLOW Message 2348|2348 ]] || [[TUFLOW Message 2349|2349 ]] || [[TUFLOW Message 2350|2350 ]] || [[TUFLOW Message 2351|2351 ]] || [[TUFLOW Message 2352|2352 ]] || [[TUFLOW Message 2353|2353 ]] || [[TUFLOW Message 2354|2354 ]] || [[TUFLOW Message 2355|2355 ]] || [[TUFLOW Message 2356|2356 ]] || [[TUFLOW Message 2357|2357 ]] || [[TUFLOW Message 2358|2358 ]] || [[TUFLOW Message 2359|2359 ]]
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|[[TUFLOW Message 2360|2360 ]] || [[TUFLOW Message 2361|2361 ]] || [[TUFLOW Message 2362|2362 ]] || 2363 || 2364 || [[TUFLOW Message 2365|2365 ]] || 2366 || [[TUFLOW Message 2367|2367 ]] || [[TUFLOW Message 2368|2368 ]] || 2369 || [[TUFLOW Message 2370|2370 ]] || [[TUFLOW Message 2371|2371 ]] || [[TUFLOW Message 2372|2372 ]] || [[TUFLOW Message 2373|2373 ]] || [[TUFLOW Message 2374|2374 ]] || [[TUFLOW Message 2375|2375 ]] || [[TUFLOW Message 2376|2376 ]] || [[TUFLOW Message 2377|2377 ]] || 2378 || 2379
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|[[TUFLOW Message 2380|2380 ]] || [[TUFLOW Message 2381|2381 ]] || [[TUFLOW Message 2382|2382 ]] || [[TUFLOW Message 2383|2383 ]] || 2384 || [[TUFLOW Message 2385|2385 ]] || [[TUFLOW Message 2386|2386 ]] || 2387 || 2388 || [[TUFLOW Message 2389|2389 ]] || [[TUFLOW Message 2390|2390 ]] || [[TUFLOW Message 2391|2391 ]] || [[TUFLOW Message 2392|2392 ]] || 2393 || 2394 || 2395 || 2396 || 2397 || 2398 || 2399
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|[[TUFLOW Message 2400|2400 ]] || [[TUFLOW Message 2401|2401 ]] || [[TUFLOW Message 2402|2402 ]] || [[TUFLOW Message 2403|2403 ]] || [[TUFLOW Message 2404|2404 ]] || [[TUFLOW Message 2405|2405 ]] || [[TUFLOW Message 2406|2406 ]] || [[TUFLOW Message 2407|2407 ]] || [[TUFLOW Message 2408|2408 ]] || [[TUFLOW Message 2409|2409 ]] || 2410 || [[TUFLOW Message 2411|2411 ]] || [[TUFLOW Message 2412|2412 ]] || [[TUFLOW Message 2413|2413 ]] || [[TUFLOW Message 2414|2414 ]] || [[TUFLOW Message 2415|2415 ]] || [[TUFLOW Message 2416|2416 ]] || [[TUFLOW Message 2417|2417 ]] || [[TUFLOW Message 2418|2418 ]] || [[TUFLOW Message 2419|2419 ]]
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|[[TUFLOW Message 2420|2420 ]] || [[TUFLOW Message 2421|2421 ]] || [[TUFLOW Message 2422|2422 ]] || [[TUFLOW Message 2423|2423 ]] || [[TUFLOW Message 2424|2424 ]] || [[TUFLOW Message 2425|2425 ]] || [[TUFLOW Message 2426|2426 ]] || [[TUFLOW Message 2427|2427 ]] || [[TUFLOW Message 2428|2428 ]] || [[TUFLOW Message 2429|2429 ]] || [[TUFLOW Message 2430|2430 ]] || [[TUFLOW Message 2431|2431 ]] || [[TUFLOW Message 2432|2432 ]] || 2433 || 2434 || [[TUFLOW Message 2435|2435 ]] || [[TUFLOW Message 2436|2436 ]] || 2437 || [[TUFLOW Message 2438|2438 ]] || 2439
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|[[TUFLOW Message 2440|2440 ]] || [[TUFLOW Message 2441|2441 ]] || [[TUFLOW Message 2442|2442 ]] || [[TUFLOW Message 2443|2443 ]] || [[TUFLOW Message 2444|2444 ]] || [[TUFLOW Message 2445|2445 ]] || 2446 || [[TUFLOW Message 2447|2447 ]] || 2448 || 2449 || [[TUFLOW Message 2450|2450 ]] || [[TUFLOW Message 2451|2451 ]] || 2452 || 2453 || 2454 || 2455 || 2456 || 2457 || 2458 || 2459
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|[[TUFLOW Message 2460|2460 ]] || [[TUFLOW Message 2461|2461 ]] || [[TUFLOW Message 2462|2462 ]] || [[TUFLOW Message 2463|2463 ]] || [[TUFLOW Message 2464|2464 ]] || [[TUFLOW Message 2465|2465 ]] || [[TUFLOW Message 2466|2466 ]] || [[TUFLOW Message 2467|2467 ]] || [[TUFLOW Message 2468|2468 ]] || [[TUFLOW Message 2469|2469 ]] || [[TUFLOW Message 2470|2470 ]] || [[TUFLOW Message 2471|2471 ]] || [[TUFLOW Message 2472|2472 ]] || [[TUFLOW Message 2473|2473 ]] || [[TUFLOW Message 2474|2474 ]] || 2475 || [[TUFLOW Message 2476|2476 ]] || [[TUFLOW Message 2477|2477 ]] || [[TUFLOW Message 2478|2478 ]] || [[TUFLOW Message 2479|2479 ]]
|-
|[[TUFLOW Message 2480|2480 ]] || [[TUFLOW Message 2481|2481 ]] || [[TUFLOW Message 2482|2482 ]] || [[TUFLOW Message 2483|2483 ]] || [[TUFLOW Message 2484|2484 ]] || [[TUFLOW Message 2485|2485 ]] || [[TUFLOW Message 2486|2486 ]] || [[TUFLOW Message 2487|2487 ]] || 2488 || [[TUFLOW Message 2489|2489 ]] || [[TUFLOW Message 2490|2490 ]] || [[TUFLOW Message 2491|2491 ]] || [[TUFLOW Message 2492|2492 ]] || [[TUFLOW Message 2493|2493 ]] || [[TUFLOW Message 2494|2494 ]] || [[TUFLOW Message 2495|2495 ]] || [[TUFLOW Message 2496|2496 ]] || [[TUFLOW Message 2497|2497 ]] || [[TUFLOW Message 2498|2498 ]] || [[TUFLOW Message 2499|2499 ]]
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|[[TUFLOW Message 2500|2500 ]] || 2501 || 2502 || 2503 || 2504 || 2505 || 2506 || [[TUFLOW Message 2507|2507 ]] || [[TUFLOW Message 2508|2508 ]] || [[TUFLOW Message 2509|2509 ]] || 2510 || 2511 || 2512 || 2513 || [[TUFLOW Message 2514|2514 ]] || [[TUFLOW Message 2515|2515 ]] || [[TUFLOW Message 2516|2516 ]] || [[TUFLOW Message 2517|2517 ]] || 2518 || [[TUFLOW Message 2519|2519 ]]
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|2520 || 2521 || [[TUFLOW Message 2522|2522 ]] || 2523 || 2524 || 2525 || 2526 || 2527 || 2528 || 2529 || 2530 || 2531 || 2532 || 2533 || 2534 || 2535 || 2536 || 2537 || 2538 || 2539
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|[[TUFLOW Message 2540|2540 ]] || [[TUFLOW Message 2541|2541 ]] || 2542 || 2543 || 2544 || 2545 || 2546 || 2547 || 2548 || 2549 || [[TUFLOW Message 2550|2550 ]] || [[TUFLOW Message 2551|2551 ]] || 2552 || 2553 || 2554 || 2555 || 2556 || 2557 || 2558 || 2559
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|[[TUFLOW Message 2560|2560 ]] || 2561 || [[TUFLOW Message 2562|2562 ]] || 2563 || [[TUFLOW Message 2564|2564 ]] || [[TUFLOW Message 2565|2565 ]] || [[TUFLOW Message 2566|2566 ]] || [[TUFLOW Message 2567|2567 ]] || [[TUFLOW Message 2568|2568 ]] || [[TUFLOW Message 2569|2569 ]] || [[TUFLOW Message 2570|2570 ]] || [[TUFLOW Message 2571|2571 ]] || [[TUFLOW Message 2572|2572 ]] || [[TUFLOW Message 2573|2573 ]] || [[TUFLOW Message 2574|2574 ]] || [[TUFLOW Message 2575|2575 ]] || [[TUFLOW Message 2576|2576 ]] || [[TUFLOW Message 2577|2577 ]] || [[TUFLOW Message 2578|2578 ]] || [[TUFLOW Message 2579|2579 ]]
|-
|[[TUFLOW Message 2580|2580 ]] || [[TUFLOW Message 2581|2581 ]] || [[TUFLOW Message 2582|2582 ]] || [[TUFLOW Message 2583|2583 ]] || [[TUFLOW Message 2584|2584 ]] || [[TUFLOW Message 2585|2585 ]] ||[[TUFLOW Message 2586|2586 ]] || [[TUFLOW Message 2587|2587 ]] || [[TUFLOW Message 2588|2588 ]] || [[TUFLOW Message 2589|2589 ]] || [[TUFLOW Message 2590|2590 ]] || 2591 ||[[TUFLOW Message 2592|2592 ]] || 2593 || [[TUFLOW Message 2594|2594 ]] || 2595 || 2596 || 2597 ||[[TUFLOW_Message_2598|2598]] || [[TUFLOW_Message_2599|2599]]
|-
|[[TUFLOW Message 2600|2600 ]] || [[TUFLOW Message 2601|2601 ]] || [[TUFLOW Message 2602|2602 ]] || [[TUFLOW Message 2603|2603 ]] || [[TUFLOW Message 2604|2604 ]] || [[TUFLOW Message 2605|2605 ]] || [[TUFLOW Message 2606|2606 ]] || [[TUFLOW Message 2607|2607 ]] || [[TUFLOW Message 2608|2608 ]] || [[TUFLOW Message 2609|2609 ]] || [[TUFLOW Message 2610|2610 ]] || [[TUFLOW Message 2611|2611 ]] || [[TUFLOW Message 2612|2612 ]] || [[TUFLOW Message 2613|2613 ]] || [[TUFLOW Message 2614|2614 ]] || [[TUFLOW Message 2615|2615 ]] || [[TUFLOW Message 2616|2616 ]] || [[TUFLOW Message 2617|2617 ]] || [[TUFLOW Message 2618|2618 ]] || [[TUFLOW Message 2619|2619 ]]
|-
|[[TUFLOW Message 2620|2620 ]] || 2621 || 2622 || 2623 || [[TUFLOW Message 2624|2624 ]] || 2625 || 2626 || 2627 || 2628 || 2629 || 2630 || [[TUFLOW Message 2631|2631 ]] || 2632 || 2633 || 2634 || 2635 || 2636 || 2637 || 2638 || 2639
|-
|2640 || [[TUFLOW Message 2641|2641 ]] || [[TUFLOW Message 2642|2642 ]] || 2643 || 2644 || 2645 || 2646 || 2647 || 2648 || [[TUFLOW Message 2649|2649 ]] || 2650 || 2651 || 2652 || 2653 || 2654 || 2655 || 2656 || 2657 || 2658 || 2659
|-
|[[TUFLOW Message 2660|2660 ]] || [[TUFLOW Message 2661|2661 ]] || [[TUFLOW Message 2662|2662 ]] || [[TUFLOW Message 2663|2663 ]] || 2664 || 2665 || 2666 || 2667 || 2668 || 2669 || [[TUFLOW Message 2670|2670 ]] || [[TUFLOW Message 2671|2671 ]] || 2672 || 2673 || 2674 || 2675 || 2676 || 2677 || 2678 || 2679
|-
| [[TUFLOW Message 2720|2720 ]] || 2721 || [[TUFLOW Message 2722|2722 ]] || 2723 || 2724 || 2725 || 2726 || 2727 || 2728 || 2729 || 2730 || 2731 || 2732 || 2733 || 2734 || [[TUFLOW Message 2735|2735 ]] || 2736 || 2737 || 2738 || 2739
|-
|2760 || 2761 || 2762 || [[TUFLOW Message 2763|2763 ]] || 2764 || 2765 || 2766 || 2767 || 2768 || 2769 || 2770 || 2771 || 2772 || 2773 || 2774 || 2775 || 2776 || 2777 || 2778 || 2779
|-
|2780 || 2781 || [[TUFLOW Message 2782|2782 ]] || 2783 || [[TUFLOW Message 2784|2784 ]] || [[TUFLOW Message 2785|2785 ]] || [[TUFLOW Message 2786|2786 ]] || [[TUFLOW Message 2787|2787 ]] || 2788 || 2789 || 2790 || 2791 || 2792 || 2793 || 2794 || 2795 || 2796 || 2797 || 2798 || 2799
|-
|[[TUFLOW Message 2800|2800 ]] || [[TUFLOW Message 2801|2801 ]] || [[TUFLOW Message 2802|2802 ]] || [[TUFLOW Message 2803|2803 ]] || [[TUFLOW Message 2804|2804 ]] || [[TUFLOW Message 2805|2805 ]] || [[TUFLOW Message 2806|2806 ]] || [[TUFLOW Message 2807|2807 ]] || [[TUFLOW Message 2808|2808 ]] || [[TUFLOW Message 2809|2809 ]] || [[TUFLOW Message 2810|2810 ]] || [[TUFLOW Message 2811|2811 ]] || [[TUFLOW Message 2812|2812 ]] || [[TUFLOW Message 2813|2813 ]] || [[TUFLOW Message 2814|2814 ]] || [[TUFLOW Message 2815|2815 ]] || [[TUFLOW Message 2816|2816 ]] || [[TUFLOW Message 2817|2817 ]] || [[TUFLOW Message 2818|2818 ]] || [[TUFLOW Message 2819|2819 ]]
|-
|[[TUFLOW Message 2820|2820 ]] || [[TUFLOW Message 2821|2821 ]] || [[TUFLOW Message 2822|2822 ]] || [[TUFLOW Message 2823|2823 ]] || [[TUFLOW Message 2824|2824 ]] || [[TUFLOW Message 2825|2825 ]] || [[TUFLOW Message 2826|2826 ]] || [[TUFLOW Message 2827|2827 ]] || [[TUFLOW Message 2828|2828 ]] || [[TUFLOW Message 2829|2829 ]] || [[TUFLOW Message 2830|2830 ]] || [[TUFLOW Message 2831|2831 ]] || [[TUFLOW Message 2832|2832 ]] || [[TUFLOW Message 2833|2833 ]] || [[TUFLOW Message 2834|2834 ]] || [[TUFLOW Message 2835|2835 ]] || [[TUFLOW Message 2836|2836 ]] || [[TUFLOW Message 2837|2837 ]] || [[TUFLOW Message 2838|2838 ]] || [[TUFLOW Message 2839|2839 ]]
|-
|[[TUFLOW Message 2840|2840 ]] || [[TUFLOW Message 2841|2841 ]] || [[TUFLOW Message 2842|2842 ]] || [[TUFLOW Message 2843|2843 ]] || [[TUFLOW Message 2844|2844 ]] || [[TUFLOW Message 2845|2845 ]] || [[TUFLOW Message 2846|2846 ]] || [[TUFLOW Message 2847|2847 ]] || [[TUFLOW Message 2848|2848 ]] || [[TUFLOW Message 2849|2849 ]] || [[TUFLOW Message 2850|2850 ]] || [[TUFLOW Message 2851|2851 ]] || [[TUFLOW Message 2852|2852 ]] || [[TUFLOW Message 2853|2853 ]] || [[TUFLOW Message 2854|2854 ]] || [[TUFLOW Message 2855|2855 ]] || [[TUFLOW Message 2856|2856 ]] || [[TUFLOW Message 2857|2857 ]] || [[TUFLOW Message 2858|2858 ]] || [[TUFLOW Message 2859|2859 ]]
|-
| 2900
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|| 2903
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|| 2906
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|| [[TUFLOW Message 2910|2910]]
|| [[TUFLOW Message 2911|2911]]
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|| [[TUFLOW Message 2913|2913]]
|| 2914
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|[[TUFLOW Message 2920|2920 ]] || [[TUFLOW Message 2921|2921 ]] || [[TUFLOW Message 2922|2922 ]] || [[TUFLOW Message 2923|2923 ]] || [[TUFLOW Message 2924|2924 ]] || [[TUFLOW Message 2925|2925 ]]|| [[TUFLOW Message 2926|2926 ]] || [[TUFLOW Message 2927|2927 ]] || [[TUFLOW Message 2928|2928 ]] || [[TUFLOW Message 2929|2929 ]] || [[TUFLOW Message 2930|2930 ]] || [[TUFLOW Message 2931|2931 ]] || [[TUFLOW Message 2932|2932 ]] || [[TUFLOW Message 2933|2933 ]] || [[TUFLOW Message 2934|2934 ]] || [[TUFLOW Message 2935|2935 ]] || [[TUFLOW Message 2936|2936 ]] || [[TUFLOW Message 2937|2937 ]] || [[TUFLOW Message 2938|2938 ]] || 2939
|-
|[[TUFLOW Message 2980|2980 ]] || 2981 || 2982 || 2983 || 2984 || 2985 || 2986 || 2987 || 2988 || 2989 || 2990 || [[TUFLOW Message 2991|2991 ]] || 2992 || 2993 || 2994 || 2995 || 2996 || 2997 || [[TUFLOW Message 2998|2998 ]] || [[TUFLOW Message 2999|2999 ]]
|-
|}
 
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4xxx TUFLOW Messages

2026-07-20T00:57:10Z

Emilie Nielsen:

The 4xxx error messages refer to errors that occur in the advection dispersion part of the model. Links to detailed message descriptions are listed in the table below. Grey numbers do not yet have a message assigned and red numbers have been allocated to new messages.

See also:
* [[0xxx TUFLOW Messages]]
* [[1xxx TUFLOW Messages]]
* [[2xxx TUFLOW Messages]]
* [[3xxx TUFLOW Messages]]
* [[5xxx TUFLOW Messages]]
* [[6xxx TUFLOW Messages]]

{| Border ="1" cellpadding="8" style="text-align:center"
|4000 || 4001 || 4002 || 4003 || 4004 || 4005 || 4006 || 4007 || 4008 || [[TUFLOW Message 4009|4009 ]] || [[TUFLOW Message 4010|4010 ]] || 4011 || 4012 || 4013 || 4014 || 4015 || [[TUFLOW Message 4016|4016 ]] || 4017 || [[TUFLOW Message 4018|4018 ]] || 4019
|-
|[[TUFLOW Message 4020|4020 ]] || [[TUFLOW Message 4021|4021 ]] || 4022 || 4023 || [[TUFLOW Message 4024|4024 ]] || 4025 || [[TUFLOW Message 4026|4026 ]] || [[TUFLOW Message 4027|4027 ]] || 4028 || [[TUFLOW Message 4029|4029 ]] || [[TUFLOW Message 4030|4030 ]] || [[TUFLOW Message 4031|4031 ]] || 4032 || [[TUFLOW Message 4033|4033 ]] || [[TUFLOW Message 4034|4034 ]] || 4035 || 4036 || 4037 || 4038 || 4039
|-
|4040 || 4041 || 4042 || 4043 || 4044 || 4045 || 4046 || 4047 || 4048 || 4049 || 4050 || 4051 || 4052 || 4053 || 4054 || 4055 || 4056 || 4057 || 4058 || 4059
|-
|4060 || 4061 || 4062 || 4063 || 4064 || 4065 || 4066 || 4067 || 4068 || 4069 || 4070 || 4071 || 4072 || 4073 || 4074 || 4075 || 4076 || 4077 || 4078 || 4079
|-
|4080 || 4081 || 4082 || 4083 || 4084 || 4085 || 4086 || 4087 || 4088 || 4089 || 4090 || 4091 || 4092 || 4093 || 4094 || 4095 || 4096 || 4097 || 4098 || 4099
|-
|4100 || 4101 || 4102 || 4103 || 4104 || 4105 || 4106 || 4107 || 4108 || 4109 || 4110 || 4111 || 4112 || 4113 || 4114 || 4115 || 4116 || 4117 || 4118 || 4119
|-
|4120 || 4121 || 4122 || 4123 || 4124 || 4125 || 4126 || 4127 || 4128 || 4129 || 4130 || 4131 || 4132 || 4133 || 4134 || 4135 || 4136 || 4137 || 4138 || 4139
|-
|4140 || 4141 || 4142 || 4143 || 4144 || 4145 || 4146 || 4147 || 4148 || 4149 || 4150 || 4151 || 4152 || 4153 || 4154 || 4155 || 4156 || 4157 || 4158 || 4159
|-
|4160 || 4161 || 4162 || 4163 || 4164 || 4165 || 4166 || 4167 || 4168 || 4169 || 4170 || 4171 || 4172 || 4173 || 4174 || 4175 || 4176 || 4177 || 4178 || 4179
|-
|4180 || 4181 || 4182 || 4183 || 4184 || 4185 || 4186 || 4187 || 4188 || 4189 || 4190 || 4191 || 4192 || 4193 || 4194 || 4195 || 4196 || 4197 || 4198 || 4199
|-
|4200 || 4201 || 4202 || 4203 || 4204 || 4205 || 4206 || 4207 || 4208 || 4209 || 4210 || 4211 || 4212 || 4213 || 4214 || 4215 || 4216 || 4217 || 4218 || 4219
|-
|4220 || 4221 || 4222 || 4223 || 4224 || 4225 || 4226 || 4227 || 4228 || 4229 || 4230 || 4231 || 4232 || 4233 || 4234 || 4235 || 4236 || 4237 || 4238 || 4239
|-
|4240 || 4241 || 4242 || 4243 || 4244 || 4245 || 4246 || 4247 || 4248 || 4249 || 4250 || 4251 || 4252 || 4253 || 4254 || 4255 || 4256 || 4257 || 4258 || 4259
|-
|4260 || 4261 || 4262 || 4263 || 4264 || 4265 || 4266 || 4267 || 4268 || 4269 || 4270 || 4271 || 4272 || 4273 || 4274 || 4275 || 4276 || 4277 || 4278 || 4279
|-
|4280 || 4281 || 4282 || 4283 || 4284 || 4285 || 4286 || 4287 || 4288 || 4289 || 4290 || 4291 || 4292 || 4293 || 4294 || 4295 || 4296 || 4297 || 4298 || 4299
|-
|4300 || 4301 || 4302 || 4303 || [[TUFLOW Message 4304|4304 ]] || 4305 || 4306 || 4307 || 4308 || 4309 || 4310 || 4311 || 4312 || 4313 || 4314 || 4315 || 4316 || 4317 || 4318 || 4319
|-
|4320 || 4321 || 4322 || 4323 || 4324 || 4325 || 4326 || 4327 || 4328 || 4329 || 4330 || 4331 || 4332 || 4333 || 4334 || 4335 || 4336 || 4337 || 4338 || 4339
|-
|4340 || 4341 || 4342 || 4343 || 4344 || 4345 || 4346 || 4347 || 4348 || 4349 || 4350 || 4351 || 4352 || 4353 || 4354 || 4355 || 4356 || 4357 || 4358 || 4359
|-
|4360 || 4361 || 4362 || 4363 || 4364 || 4365 || 4366 || 4367 || 4368 || 4369 || 4370 || 4371 || 4372 || 4373 || 4374 || 4375 || 4376 || 4377 || 4378 || 4379
|-
|4380 || 4381 || 4382 || 4383 || 4384 || 4385 || 4386 || 4387 || 4388 || 4389 || 4390 || 4391 || 4392 || 4393 || 4394 || 4395 || 4396 || 4397 || 4398 || 4399
|-
|}
 
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TUFLOW Message 4026

2026-07-20T00:57:03Z

Emilie Nielsen: Created page with "{{TUFLOW_Message |tuflow_message=ERROR 4026 - "If Scenario" / "If Event" not yet currently supported in TUFLOW-AD control file (.adcf). |alt_msg=NA |type=ERROR |message_desc="If Scenario" and/or "If Event" commands are not supported in .adcf (TUFLOW AD control file). |suggestions=Use "If Scenario" and/or "If Event" in the .tcf file to specify different .adcf files for each scenario/event. For example, <tt>If Scenario == </fo..."

{{TUFLOW_Message
|tuflow_message=ERROR 4026 - "If Scenario" / "If Event" not yet currently supported in TUFLOW-AD control file (.adcf).
|alt_msg=NA

|type=[[ERROR]]
|message_desc="If Scenario" and/or "If Event" commands are not supported in .adcf (TUFLOW AD control file).
|suggestions=Use "If Scenario" and/or "If Event" in the .tcf file to specify different .adcf files for each scenario/event. For example,

<tt>If Scenario == opA</tt>
:<tt>AD Control File == ..\model\example_opA_001.adcf</tt>
<tt>Else If Scenario == opB</tt>
:<tt>AD Control File == ..\model\example_opB_001.adcf</tt>
<tt>End If

|uplink=[[4xxx_TUFLOW_Messages|4xxx Messages]]
}}

TUFLOW Message 4034

2026-07-20T00:52:13Z

Emilie Nielsen: Created page with "{{TUFLOW_Message |tuflow_message=ERROR 4034 - Number of 1d node missmatch. |alt_msg=NA |type=ERROR |message_desc= |suggestions= |uplink=4xxx Messages }}"

{{TUFLOW_Message
|tuflow_message=ERROR 4034 - Number of 1d node missmatch.
|alt_msg=NA

|type=[[ERROR]]
|message_desc=
|suggestions=

|uplink=[[4xxx_TUFLOW_Messages|4xxx Messages]]
}}

TUFLOW Message 4024

2026-07-20T00:37:22Z

Emilie Nielsen: Created page with "{{TUFLOW_Message |tuflow_message=ERROR 4024 - "If Scenario" / "If Event" syntax not yet currently supported in .tbc file when using TUFLOW-AD. |alt_msg=NA |type=ERROR |message_desc="If Scenario" and/or "If Event" commands are not supported in .tbc file when using TUFLOW AD (Advection Dispersion). |suggestions=Use "If Scenario" and/or "If Event" in the .tcf file to specify different .tbc files for each scenario/event. For example, <tt>If Scenario</..."

{{TUFLOW_Message
|tuflow_message=ERROR 4024 - "If Scenario" / "If Event" syntax not yet currently supported in .tbc file when using TUFLOW-AD.
|alt_msg=NA

|type=[[ERROR]]
|message_desc="If Scenario" and/or "If Event" commands are not supported in .tbc file when using TUFLOW AD (Advection Dispersion).
|suggestions=Use "If Scenario" and/or "If Event" in the .tcf file to specify different .tbc files for each scenario/event. For example,

<tt>If Scenario == opA</tt>
:<tt>BC Control File == ..\model\example_opA_001.tbc</tt>
<tt>Else If Scenario == opB</tt>
:<tt>BC Control File == ..\model\example_opB_001.tbc</tt>
<tt>End If

|uplink=[[4xxx_TUFLOW_Messages|4xxx Messages]]
}}

Tutorial M11 001 Results QGIS TUFLOW Viewer V2

2026-06-23T23:28:17Z

Emilie Nielsen: /* Method */

=Introduction=
QGIS and TUFLOW Viewer V2 is used to view the water level in the 1D network, moving between the 1D and 2D and in the 2D floodplain. For viewing of the 2D map results, see [[Tutorial_M01_Results_QGIS_TUFLOW_Viewer_V2 | Module 1]]. 
 

=Method=
Inspect water level and velocity outputs:
<ol>
<li>Open the Map Outputs and Time Series results, either:
*Within the QGIS Browser Panel drag the following layers into the QGIS workspace, or
::* '''Module_11\TUFLOW\results\M11_5m_001.xmdf''' > loads the map output
::* '''Module_11\TUFLOW\results\plot\M11_5m_001.tpc''' > loads the time series output results
* In File Explorer, navigate to the files above and drag and drop them into the QGIS workspace.
<li>In the Layers panel, select '''M11_5m_001'''. Then in the Layer Styling panel, select the 'Depth' and 'Vector Velocity' output types in the 'Datasets' tab. 
The resolution of the vector velocity is different between the 1D and 2D sections. The 1D section shows vectors at the water level lines (2d_WLL) every 2.5m, the 2D section shows vectors based on the 2D cell resolution, every 5m. The direction of the vectors show water moving between the 1D and 2D: 
 
{{Video|name=32_Animation_M11_001_Results_Video1_V2_b.mp4|width=1264}} 
 
<li>Use the Profile Plot tool to see a long profile of water through the 1D open channel. Select 'Water Level', 'Max Water Level', 'Bed Level' and 'Pipes' from the Data Types.
<li>Select a section of open channel by clicking on an upstream and downstream PLOT_L result by holding shift. If only one line is selected, the tool plots the entire open channel downstream of the selected line: 
 
{{Video|name=33_Animation_M11_001_Results_Video2_V2_b.mp4|width=1231}} 
 
<li>Use the Time Series Plot tool to see the time series of the flow at the reporting location and open channel PLOT_L line. The reporting location shows the total flow across the line in both the 1D and 2D. The open channel line shows flow only through the 1D. 
 
{{Video|name=34_Animation_M11_001_Results_Video3_V2_a.mp4|width=1231}} 
 
<li>Use the Time Series Plot tool to see the time series of the water level at the reporting location point. When snapped to 1D channel start/end, it shows the 1D water level. Not snapped it would show the 2D water level. 
 
{{Video|name=35_Animation_M11_001_Results_Video4_V2_a.mp4|width=1231}} 
 
</ol>

=Conclusion=
:*Depth and velocity map outputs from the 1D and 2D were inspected using TUFLOW Viewer V2.
:*A long section of water level through the 1D results was plotted.
:*Time series of flow was inspected at the reporting location and compared with flow in the 1D channel.
:*For further functionality, see [https://docs.tuflow.com/qgis-tuflow-plugin/latest/tuflow-viewer TUFLOW Viewer documentation].
 

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|uplink=[[Tutorial_M11#Results| Back to Module 11 Main Page]]
}}

Tutorial M10 003 Results QGIS TUFLOW Viewer V2

2026-06-23T23:26:04Z

Emilie Nielsen: /* Method */

=Introduction=
QGIS is used to view the depth, velocity and water levels with the TUFLOW Viewer V2. For viewing of the 2D map results, see [[Tutorial_M01_Results_QGIS_TUFLOW_Viewer_V2 | Module 1]]. 
 

=Method=

Inspect depth, velocity and water level outputs:
<ol>
<li>Open the Map Outputs and Plot Output results, either:
*Within the QGIS Browser Panel drag the following layers into the QGIS workspace, or
:* '''Module_10\TUFLOW\results\M10_5m_003.xmdf''' > loads the map output mesh results
:* '''Module_10\TUFLOW\results\plot\M10_5m_003.tpc''' > loads the time series output results
* In File Explorer, navigate to the files above and drag and drop them into the QGIS workspace.
<li>In the Layers panel, select '''M10_5m_003'''. Then in the Layer Styling panel, select the 'Depth' and 'Vector Velocity' output types in the 'Datasets' tab. 
<li>Click on the 'TUFLOW Viewer Plot Window' [[File:results_2.png | 15px]] icon. The plot widget will open. 
<li>Use the Time Series Plot tool to see the time series of the flow at the location of the piping failure and dam failure. The time series shows the initial piping failure, followed by the dam failure: 
 
{{Video|name=28_Animation_M10_003_Results_V2_a.mp4|width=1215}} 
</ol> 

=Conclusion=
:*The depth, velocity and flow were inspected over time at the location of the piping and dam failure using TUFLOW Viewer V2.
:*For further functionality, see [https://docs.tuflow.com/qgis-tuflow-plugin/latest/tuflow-viewer TUFLOW Viewer documentation].
 

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Tutorial M10 001 Results QGIS TUFLOW Viewer V2

2026-06-23T23:16:14Z

Emilie Nielsen: /* Method */

=Introduction=
QGIS is used to view the dam break scenario via the bathymetry (the 'dynamic bed levels') and water depth with the TUFLOW Viewer V2. For viewing of the 2D map results, see [[Tutorial_M01_Results_QGIS_TUFLOW_Viewer_V2 | Module 1]]. 
 

=Method=
Inspect bathymetry (dynamic bed elevation) and water depth outputs:
<ol>
<li>Open the Map Outputs results, either:
*Within the QGIS Browser Panel drag the following layer into the QGIS workspace, or
::* '''Module_10\TUFLOW\results\M10_5m_001.xmdf''' > loads the map output
* In File Explorer, navigate to the file above and drag and drop it into the QGIS workspace.
<li>In the Layers panel, select '''M10_5m_001'''. Then in the Layer Styling panel, select the 'Bathymetry' output type in the 'Datasets' tab. It shows elevations at cell corners (ZH points) over time based in the variable geometry (2d_vzsh).
<li>Click on the 'TUFLOW Viewer Plot Window' [[File:results_2.png | 15px]] icon. The plot widget will open. 
<li>Use the Cross Section Plot tool to plot the 'bed elevation' and 'dynamic bed elevation' (elevation at the beginning of the simulation) at the location of the dam break. The dam break begins at 1 hour and takes 15 minutes to fully develop: 
 
{{Video|name=24_Animation_M10_001_Results_Video1_V2_b.mp4|width=1264}} 
 
<li>In the Layers panel, select '''M10_5m_001'''. Then select the 'Depth' output type in the 'Datasets' tab. Use the Time Series Plot tool to see the time series of the 'dynamic bed level' and 'water level' at the location of the dam break, whilst viewing the depth result type. Due to the IWL, water is within the dam at the beginning of the simulation 
 
{{Video|name=25_Animation_M10_001_Results_Video2_V2_a.mp4|width=1264}} 
 
</ol>

=Conclusion=
:*A cross section of the dam wall was inspected showing the bathymetry changing over time using TUFLOW Viewer V2.
:*Time series of bathymetry and water level were inspected at the location of the dam break.
:*For further functionality, see [https://docs.tuflow.com/qgis-tuflow-plugin/latest/tuflow-viewer TUFLOW Viewer documentation].
 

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|uplink=[[Tutorial_M10#Results| Back to Module 10 Main Page]]
}}

Tutorial M09 Results QGIS TUFLOW Viewer V2

2026-06-23T23:14:48Z

Emilie Nielsen: /* Method */

=Introduction=
QGIS is used to load and view a range of event magnitudes and durations with the TUFLOW Viewer V2. For viewing of the 2D map results, see [[Tutorial_M01_Results_QGIS_TUFLOW_Viewer_V2 | Module 1]]. 
 

= TUFLOW Project Re-Configuration =
<ol>
<li>Set the QGIS workspace projection to EPSG:32760, see [[Tutorial_Site_Familiarisation_QGIS#Set_the_Projection | Set the Projection]].
<li>Save the QGIS workspace by selecting Project > Save As. 
</ol>
 

=Method=
Inspect the results for all events:
<ol>
<li>Open the Map Outputs and Plot Output results, either:
*Within the QGIS Browser Panel drag the following layers into the QGIS workspace, or
::* '''Module_09\TUFLOW\results\M09_5m_05p_1hr_001.xmdf''' > loads the 1% AEP 1hr map output mesh results
::* '''Module_09\TUFLOW\results\M09_5m_05p_2hr_001.xmdf''' > loads the 1% AEP 2hr map 1hr output mesh results
::* '''Module_09\TUFLOW\results\M09_5m_02p_1hr_001.xmdf''' > loads the 2% AEP 1hr map output mesh results
::* '''Module_09\TUFLOW\results\M09_5m_02p_2hr_001.xmdf''' > loads the 2% AEP 2hr map output mesh results
::* '''Module_09\TUFLOW\results\M09_5m_01p_1hr_001.xmdf''' > loads the 5% AEP 1hr map output mesh results
::* '''Module_09\TUFLOW\results\M09_5m_01p_2hr_001.xmdf''' > loads the 5% AEP 2hrmap output mesh results
::* '''Module_09\TUFLOW\results\plot\M09_5m_01p_1hr_001.tpc''' > loads the plot output results for the 1% AEP 1hr simulation
::* '''Module_09\TUFLOW\results\plot\M09_5m_01p_2hr_001.tpc''' > loads the plot output results for the 1% AEP 2hr simulation
* In File Explorer, navigate to the files above and drag and drop them into the QGIS workspace.
<li>The TUFLOW Viewer V2 displays all six simulation runs using event management: 
 
{{Video|name=22_Animation_M09_Results_V2_b.mp4|width=1264}} 
 
<li>Click on the 'TUFLOW Viewer Plot Window' [[File:results_2.png | 15px]] icon. The plot widget will open. 
<li>Inspect the 'extent', 'water level' and the 'flow' plot output for each event: 
 
{{Video|name=23_Animation_M09_Results_Flow_V2_c.mp4|width=1264}} 
 
</ol>

=Conclusion=
:*The results of all event magnitudes and durations were inspected using the TUFLOW Viewer V2.
:*For further functionality, see [https://docs.tuflow.com/qgis-tuflow-plugin/latest/tuflow-viewer TUFLOW Viewer documentation].
 

{{Tips Navigation
|uplink=[[Tutorial_M09#Results| Back to Module 9 Main Page]]
}}

Tutorial M08 001 Results QGIS TUFLOW Viewer V2

2026-06-23T23:13:40Z

Emilie Nielsen: /* Method */

=Introduction=
QGIS is used to load and view the 10m, 5m and 2.5m scenarios with the TUFLOW Viewer V2. For viewing of the 2D map results, see [[Tutorial_M01_Results_QGIS_TUFLOW_Viewer_V2 | Module 1]]. 
 

=Method=
Inspect the results from each scenario:
<ol>
<li>Open the Map Outputs and Plot Output results, either:
*Within the QGIS Browser Panel drag the following layers into the QGIS workspace, or
::* '''Module_08\TUFLOW\results\M08_10m_001.xmdf''' > loads the map output for the 10m mesh results
::* '''Module_08\TUFLOW\results\M08_5m_001.xmdf''' > loads the map output for the 5m mesh results
::* '''Module_08\TUFLOW\results\M08_2.5m_001.xmdf''' > loads the map output for the 2.5m mesh results
::* '''Module_08\TUFLOW\results\plot\M08_10m_001.tpc''' > loads the time series output results for the 10m model
::* '''Module_08\TUFLOW\results\plot\M08_5m_001.tpc''' > loads the time series output results for the 5m model
::* '''Module_08\TUFLOW\results\plot\M08_2.5m_001.tpc''' > loads the time series output results for the 2.5m model
* In File Explorer, navigate to the files above and drag and drop them into the QGIS workspace.
<li>Inspect the resolution of the results at the edges of the floodplain, the resolution is finer for the 2.5m simulation; e.g. the '''M08_2.5m_001.xmdf''' results show a finer resolution than the '''M08_5m_001.xmdf''' and the '''M08_10m_001.xmdf'''.
 
{{Video|name=19_Animation_M08_Results_Part 1_V2_b.mp4|width=1264}} 
 
<li>Inspect the timeseries of the flow at the plot output: 
 
{{Video|name=20_Animation_M08_Results_Part 1__002_V2_b.mp4|width=1264}} 
 
</ol>

=Conclusion=
:*The results of the 10m, 5m and 2.5m scenarios were inspected using the TUFLOW Viewer V2.
:*For further functionality, see [https://docs.tuflow.com/qgis-tuflow-plugin/latest/tuflow-viewer TUFLOW Viewer documentation].
 

{{Tips Navigation
|uplink=[[Tutorial_M08#Results| Back to Module 8 Main Page]]
}}

Tutorial M08 001 Results QGIS TUFLOW Viewer V2

2026-06-23T23:12:47Z

Emilie Nielsen: /* Method */

=Introduction=
QGIS is used to load and view the 10m, 5m and 2.5m scenarios with the TUFLOW Viewer V2. For viewing of the 2D map results, see [[Tutorial_M01_Results_QGIS_TUFLOW_Viewer_V2 | Module 1]]. 
 

=Method=
Inspect the results from each scenario:
<ol>
<li>Open the Map Outputs and Plot Output results, either:
*Within the QGIS Browser Panel drag the following layers into the QGIS workspace, or
::* '''Module_08\TUFLOW\results\M08_10m_001.xmdf''' > loads the map output for the 10m mesh results
::* '''Module_08\TUFLOW\results\M08_5m_001.xmdf''' > loads the map output for the 5m mesh results
::* '''Module_08\TUFLOW\results\M08_2.5m_001.xmdf''' > loads the map output for the 2.5m mesh results
::* '''Module_08\TUFLOW\results\plot\M08_10m_001.tpc''' > loads the time series output results for the 10m model
::* '''Module_08\TUFLOW\results\plot\M08_5m_001.tpc''' > loads the time series output results for the 5m model
::* '''Module_08\TUFLOW\results\plot\M08_2.5m_001.tpc''' > loads the time series output results for the 2.5m model
* In File Explorer, navigate to the files above and drag and drop them into the QGIS workspace.
<li>Inspect the resolution of the results at the edges of the floodplain, the resolution is finer for the 2.5m simulation; e.g. the '''M08_2.5m_001.xmdf''' results show a finer resolution than the '''M08_5m_001.xmdf''' and the '''M08_10m_001.xmdf'''.
 
{{Video|name=19_Animation_M08_Results_Part 1_V2_b.mp4|width=1264}} 
 
<li>Inspect the timeseries of the flow at the plot output: 
 
{{Video|name=20_Animation_M08_Results_Part 1__002_V2_b.mp4|width=1264}} 
 
</ol> 

=Conclusion=
:*The results of the 10m, 5m and 2.5m scenarios were inspected using the TUFLOW Viewer V2.
:*For further functionality, see [https://docs.tuflow.com/qgis-tuflow-plugin/latest/tuflow-viewer TUFLOW Viewer documentation].
 

{{Tips Navigation
|uplink=[[Tutorial_M08#Results| Back to Module 8 Main Page]]
}}

Tutorial M06 003 Results QGIS TUFLOW Viewer V2

2026-06-23T22:56:22Z

Emilie Nielsen:

=Introduction=
QGIS is used to view the cumulative rainfall, rainfall rate and material rainfall losses with the TUFLOW Viewer V2. For viewing of the 2D map results, see [[Tutorial_M01_Results_QGIS_TUFLOW_Viewer_V2 | Module 1]]. 
 

=Method=
Inspect cumulative rainfall and rainfall rate outputs:
<ol>
<li>Open the Plot Output results, by either:
*Within the QGIS Browser Panel drag the following layers into the QGIS workspace, or
::*'''Module_06\TUFLOW\results\M06_5m_003.xmdf''' > loads the map output mesh results (used for viewing purposes)
::*'''Module_06\TUFLOW\results\plot\M06_5m_003.tpc''' > loads the plot output results
* In File Explorer, navigate to the files above and drag and drop them into the QGIS workspace.
<li>Select the '''M06_5m_003''' file in the Layers panel and click on the 'TUFLOW Viewer Plot Window' [[File:results_2.png | 15px]] icon. The plot widget will open. 
<li>Select the Data Types 'rf cumulative' (cumulative rainfall) and 'rf rate' (rainfall rate) and use the 'Draw tool' to select a location. Notice they vary spatially based on the distance to the points within the 2d_rf point file: 
 
{{Video|name=17a_Animation_M06_Results_Part3_V2_b.mp4|width=1264}} 
 
</ol>

=Conclusion=
:*The cumulative rainfall and rainfall rate derived from gridded rainfall were inspected with the TUFLOW Viewer V2.
:*For further functionality, see [https://docs.tuflow.com/qgis-tuflow-plugin/latest/tuflow-viewer TUFLOW Viewer documentation].
 

{{Tips Navigation
|uplink=[[Tutorial_M06#Results_3| Back to Module 6 Main Page]]
}}

Tutorial M04 Results QGIS TUFLOW Viewer V2

2026-06-23T22:52:24Z

Emilie Nielsen: /* Method */

= Introduction =
QGIS is used to view the head loss across the 2D bridge with the TUFLOW Viewer V2. For viewing of the 2D map results, see [[Tutorial_M01_Results_QGIS_TUFLOW_Viewer_V2 | Module 1]]. 
 

= Method =
Plot head loss across the 2D bridge: 
<ol>
<li>Open the Map Outputs and Plot Output results, either:
*Within the QGIS Browser Panel drag the following layers into the QGIS workspace, or
::* '''Module_04\TUFLOW\results\M04_5m_001.xmdf''' > loads the map output mesh results
::* '''Module_04\TUFLOW\results\plot\M04_5m_001.tpc''' > loads the time series output results
* In File Explorer, navigate to the files above and drag and drop them into the QGIS workspace.
<li>Select the '''M04_5m_001''' file in the Layers panel and click on the 'TUFLOW Viewer Plot Window' [[File:results_2.png | 15px]] icon. The plot widget will open. 
<li>Open the Section Plot [[File:results_lp_v2.png | 15px]] tab, select the Data Type 'water level' and use the 'Draw' [[File:TUFLOW Viewer 2 Draw icon_2.png | 20px]] tool to see head loss across the 2d_lfcsh: 
 
{{Video|name=08_Animation_M04_Results_V2_c.mp4|width=1264}} 
</ol>
Review structure group outputs:
<ol>
<li>Select the '''M04_5m_001_Plot_L''' file in the Layers panel and click on the 'TUFLOW Viewer Plot Window' [[File:results_2.png | 15px]] icon. The plot widget will open. 
To plot the structure flow and the upstream and downstream water levels, use the 'Time Series' tab and select the Data Types 'Structure Flow', 'u-s Structure Water Level' and 'd-s Structure Water Level'. Use the 'Selection' [[File:TUFLOW Viewer 2 Selection icon_2.png | 30px]] tool, to select the 2d_po line, which will display the data.
 
'''Note: '''Right click on the graph to select 'Show current time'. To display a graph on a secondary axis, select a specific graph and click on 'Move to secondary axis'. 
Use the QGIS 'Temporal Controller' to go through the timesteps. The 'Temporal Controller' has multiple functionalities. Click on the 'play' button to start the animation and automatically step though the time steps. Or select the 'Go to next frame' button to click through. Or use the mouse to go through or select certain time steps. The time step interval can be changed using the 'Step' window.
{{Video|name=09_Animation_M04_Results_Bridge_V2_b.mp4|width=1264}} 
 
<li>Navigate to '''Module_04\TUFLOW\results\plot\csv''' and open '''M04_5m_001_SHmx.csv'''. It contains a summary of each structure when the upstream water level reaches its maximum. The output columns include:
:*Flow, area and average velocity for below and above deck.
:*Total flow, area and average velocity for the whole structure.
:*Upstream and downstream water levels and the head drop across the structure (i.e. upstream minus downstream water level).
:*The time this data was recorded (i.e. the time the upstream water level peaked). 
The structure group output associates the 2d_po points and line with the same Label 'Bridge': 
 
[[File:M04_Results_03b.png]]
 
</ol>

= Conclusion =
:*The plot cross-section tool was used to view the head loss across the layered flow constriction.
:*A plot was made showing structure flow and the upstream and downstream water levels at layered flow constriction.
:*The _SHmx csv file was inspected showing a summary of the structure when the upstream water level reached its maximum.
:*For further functionality, see [https://docs.tuflow.com/qgis-tuflow-plugin/latest/tuflow-viewer TUFLOW Viewer documentation].

 
{{Tips Navigation
|uplink=[[Tutorial_M04#Results| Back to Module 4 Main Page]]
}}

Tutorial M04 Results QGIS TUFLOW Viewer V2

2026-06-23T22:51:57Z

Emilie Nielsen: /* Method */

= Introduction =
QGIS is used to view the head loss across the 2D bridge with the TUFLOW Viewer V2. For viewing of the 2D map results, see [[Tutorial_M01_Results_QGIS_TUFLOW_Viewer_V2 | Module 1]]. 
 

= Method =
Plot head loss across the 2D bridge: 
<ol>
<li>Open the Map Outputs and Plot Output results, either:
*Within the QGIS Browser Panel drag the following layers into the QGIS workspace, or
::* '''Module_04\TUFLOW\results\M04_5m_001.xmdf''' > loads the map output mesh results
::* '''Module_04\TUFLOW\results\plot\M04_5m_001.tpc''' > loads the time series output results
* In File Explorer, navigate to the files above and drag and drop them into the QGIS workspace.
<li>Select the '''M04_5m_001''' file in the Layers panel and click on the 'TUFLOW Viewer Plot Window' [[File:results_2.png | 15px]] icon. The plot widget will open. 
<li>Open the Section Plot [[File:results_lp_v2.png | 15px]] tab, select the Data Type 'water level' and use the 'Draw' [[File:TUFLOW Viewer 2 Draw icon_2.png | 20px]] tool to see head loss across the 2d_lfcsh: 
 
{{Video|name=08_Animation_M04_Results_V2_c.mp4|width=1264}} 
</ol>

Review structure group outputs:
<ol>
<li>Select the '''M04_5m_001_Plot_L''' file in the Layers panel and click on the 'TUFLOW Viewer Plot Window' [[File:results_2.png | 15px]] icon. The plot widget will open. 
To plot the structure flow and the upstream and downstream water levels, use the 'Time Series' tab and select the Data Types 'Structure Flow', 'u-s Structure Water Level' and 'd-s Structure Water Level'. Use the 'Selection' [[File:TUFLOW Viewer 2 Selection icon_2.png | 30px]] tool, to select the 2d_po line, which will display the data.
 
'''Note: '''Right click on the graph to select 'Show current time'. To display a graph on a secondary axis, select a specific graph and click on 'Move to secondary axis'. 
Use the QGIS 'Temporal Controller' to go through the timesteps. The 'Temporal Controller' has multiple functionalities. Click on the 'play' button to start the animation and automatically step though the time steps. Or select the 'Go to next frame' button to click through. Or use the mouse to go through or select certain time steps. The time step interval can be changed using the 'Step' window.
{{Video|name=09_Animation_M04_Results_Bridge_V2_b.mp4|width=1264}} 
 
<li>Navigate to '''Module_04\TUFLOW\results\plot\csv''' and open '''M04_5m_001_SHmx.csv'''. It contains a summary of each structure when the upstream water level reaches its maximum. The output columns include:
:*Flow, area and average velocity for below and above deck.
:*Total flow, area and average velocity for the whole structure.
:*Upstream and downstream water levels and the head drop across the structure (i.e. upstream minus downstream water level).
:*The time this data was recorded (i.e. the time the upstream water level peaked). 
The structure group output associates the 2d_po points and line with the same Label 'Bridge': 
 
[[File:M04_Results_03b.png]]
 
</ol>

= Conclusion =
:*The plot cross-section tool was used to view the head loss across the layered flow constriction.
:*A plot was made showing structure flow and the upstream and downstream water levels at layered flow constriction.
:*The _SHmx csv file was inspected showing a summary of the structure when the upstream water level reached its maximum.
:*For further functionality, see [https://docs.tuflow.com/qgis-tuflow-plugin/latest/tuflow-viewer TUFLOW Viewer documentation].

 
{{Tips Navigation
|uplink=[[Tutorial_M04#Results| Back to Module 4 Main Page]]
}}

Tutorial M03 Results QGIS TUFLOW Viewer V2

2026-06-23T22:51:15Z

Emilie Nielsen: /* Conclusion */

= Introduction =
QGIS is used to view the 1D time series results with the TUFLOW Viewer V2. For viewing of the 2D map results, and activating TUFLOW Viewer V2, see [[Tutorial_M01_Results_QGIS_TUFLOW_Viewer_V2 | Module 1]]. 
 

= Method =
Plot Time Series results through the culverts:
<ol>
<li>Open the Map Outputs and Plot Output results, either:
*Within the QGIS Browser Panel drag the following layers into the QGIS workspace, or
::* '''Module_03\TUFLOW\results\M03_5m_001.xmdf''' > loads the map output mesh results
::* '''Module_03\TUFLOW\results\plot\M03_5m_001.tpc''' > loads the time series output results
* In File Explorer, navigate to the files above and drag and drop them into the QGIS workspace.

<li>Select the '''M03_5m_001_PLOT_L''' file in the Layers panel and click on the 'TUFLOW Viewer Plot Window' [[File:results_2.png | 15px]] icon. The plot widget will open.
<li> Select the Data Types [[File:TUFLOW Viewer 2 Data Types icon.png | 30px]] icon and click on 'Flow', then using the 'Selection' [[File:TUFLOW Viewer 2 Selection icon_2.png | 30px]] tool highlight one of the 1d_nwk lines. 
 
{{Video|name=06_Animation_M03_Results_Flow_V2_b.mp4|width=1264}} 

</ol>
Click the plus symbol next to the time series tab and select the [[File:results_lp_v2.png | 15px]] Cross Section Plot tool: 
<ol>
<li> Select the Data Types [[File:TUFLOW Viewer 2 Data Types icon.png | 30px]] icon and click on 'Bed Level, Max Water Level, Water Level, Pipes', then using the 'Selection' tool highlight one of the 1d_nwk lines. 
 
{{Video|name=07_Animation_M03_Results_Levels_Bed_Pipe_V2_c.mp4|width=1264}} 
</ol>
 

= Conclusion =
:*The 1D results were assessed including time series and long profile results using TUFLOW Viewer V2.
:*For further functionality, see [https://docs.tuflow.com/qgis-tuflow-plugin/latest/tuflow-viewer TUFLOW Viewer documentation].

 
{{Tips Navigation
|uplink=[[Tutorial_M03#Results| Back to Module 3 Main Page]]
}}

Tutorial M09 Results QGIS

2026-06-23T00:07:47Z

Emilie Nielsen: /* TUFLOW Project Re-Configuration */

=Introduction=
QGIS is used to load and view a range of event magnitudes and durations with the TUFLOW Viewer. For viewing of the 2D map results, see [[Tutorial_M01_Results_QGIS | Module 1]]. 
 

= TUFLOW Project Re-Configuration =
<ol>
<li>Set the QGIS workspace projection to EPSG:32760, see [[Tutorial_Site_Familiarisation_QGIS#Set_the_Projection | Set the Projection]].
<li>Save the QGIS workspace by selecting Project > Save As. 
</ol>
 

=Method=
Inspect the results for all events:
<ol>
<li>Open the TUFLOW Viewer.
<li>Load the results using the TCF. From File > Load Results, navigate to the '''Module_09\TUFLOW\runs''' folder and select the following file:
:*'''M09_5m_~e1~_~e2~_001.tcf'''
<li>When prompted, click 'Select All' and 'Ok'. The TUFLOW Viewer opens all six simulation runs using event management: 
 
{{Video|name=Animation_M09_Results_01b.mp4|width=1224}} 
 
<li>Inspect the extent, water level and the flow plot output for each event: 
 
{{Video|name=Animation_M09_Results_02b.mp4|width=1224}} 
 
</ol> 

=Conclusion=
:*The results of all event magnitudes and durations were inspected using the TUFLOW Viewer.
:*For further functionality, see [[TUFLOW_Viewer | TUFLOW Viewer]]. 
 

{{Tips Navigation
|uplink=[[Tutorial_M09#Results| Back to Module 9 Main Page]]
}}

TUFLOW CATCH Tutorial Introduction

2026-06-02T01:23:04Z

Emilie Nielsen: Reverted edits by Emilie Nielsen (talk) to last revision by Pavlina Monhartova

= Introduction =
The following tutorial models are aimed at new and experienced users, stepping through the process of building and running TUFLOW CATCH together. These tutorials aim to demonstrate the power and flexibility of TUFLOW CATCH in simulating catchment-wide hydrologic, hydraulic, pollutant export, and receiving waterway processes. TUFLOW CATCH enables detailed simulation of surface and subsurface flows, pollutant transport, and downstream environmental impact without relying on lumped or average assumptions.

'''Note: Users new to TUFLOW are encouraged to first complete Module 1, 2, 3 and 6 of the [[Tutorial_Introduction | TUFLOW Tutorials]]. These modules cover key concepts in 1D and 2D modeling, as well as direct rainfall models.'''

=Software Requirements=
TUFLOW uses QGIS as its Graphical User Interface (GUI), in combination with text editor and spreadsheet software, for its model creation and result viewing. The group of software creates an extremely workflow efficient and flexible modeling environment. Notably, QGIS does not experience the data load/visualization lag and display issues some other hydraulic modeling software GUI's are limited by when working with larger datasets. 

{| class="wikitable" width="75%"

! style="background-color:#005581; font-weight:bold; color:white;"| Requirement
! style="background-color:#005581; font-weight:bold; color:white;" | Brief Description
! style="background-color:#005581; font-weight:bold; color:white;" | Download
|-
| '''TUFLOW''' || TUFLOW is a computer program for simulating depth-averaged, one and two-dimensional free-surface flows such as occurs from floods and tides, with the 2D solution occurring over a regular grid or quadtree mesh of square elements. 
It is recommended to always use the latest release version of TUFLOW. 

This tutorial model does not require a TUFLOW license. 

This tutorial is configured to use a NVIDIA GPU card. If this is not available, your CPU can be used via the Hardware command.
This tutorial is set up to use a NVIDIA GPU card. If this is not available, the simulations can be run on CPU using the <tt>Hardware == CPU</tt> command.
||The TUFLOW executable is provided within the [[TUFLOW_CATCH_Tutorial_Introduction#Tutorial_Data | Tutorial Download Dataset]].
|-
| '''QGIS''' QGIS TUFLOW plugin QGIS TUFLOW CATCH plugin || QGIS is the Geographic Information System (GIS) Graphical User Interface (GUI) used to build models and view results. The QGIS TUFLOW plugin includes numerous tools to increase workflow efficiency. The QGIS TUFLOW CATCH plugin includes CATCH specific tools.

This tutorial was developed using QGIS 3.42, QGIS TUFLOW plugin 3.14 and QGIS TUFLOW CATCH plugin 0.48. Please use these or newer versions of QGIS and the plugins.

||[https://qgis.org/download/ Latest 64-bit version of QGIS]. 

[[TUFLOW_QGIS_Plugin| QGIS TUFLOW Plugin Installation]]. 

[https://downloads.tuflow.com/Private_Download/tuflow_catch_plugin/tuflow_catch.zip QGIS TUFLOW CATCH Plugin]. For instructions on installing a plugin from a ZIP, see [[Installing_the_Latest_Development_Version_of_the_TUFLOW_Plugin#How_to_install_the_Development_Plugin_Version |Install from ZIP]].
|-
| '''NotePad++''' Syntax Highlighting || A text editor is required for creation of the TUFLOW control (script) files. This tutorial was developed with NotePad++. Ideally a text editor should be able to: 
*Color code the TUFLOW control files;
*Open other files from the active control file; and
*Launch a TUFLOW simulation. 
TUFLOW color coding can be enabled using syntax highlighting.
|| [https://notepad-plus-plus.org/downloads/ Latest 64-bit version of Notepad++]. 

[https://downloads.tuflow.com/_archive/Miscellaneous/NPP_TUFLOW_Syntax_Highlighting.zip TUFLOW syntax highlighting for Notepad++]. 

For instructions on configuring Notepad++ for TUFLOW modeling, see [[NotepadPlusPlus_Tips |Notepad++ tips]].
|-
| '''Microsoft Excel''' || A spreadsheet software is required for working with tabular data and .csv files. This tutorial has been created using Excel. ||
|}

=Tutorial Data=
To build the tutorial model, download the dataset below. This includes a digital elevation model (DEM), aerial photography, background model data for the tutorial models and a working version of each model.
:*[https://downloads.tuflow.com/TUFLOW/Wiki_Tute_Models/TUFLOW_CATCH_Tutorial_Models.zip TUFLOW CATCH Tutorial Dataset - QGIS]

=Tutorial Modules=
The download dataset contains the input files and working version of the tutorial models for reference. Results and check files are not included to keep the size of the download file manageable; they will be created when running the model simulations. The folder should be placed in a location with write permissions. 

There are four tutorial models. All models can be completed independently, however it is encouraged to complete them in sequence:

:*[[TUFLOW_CATCH_Tutorial_M01 | TUFLOW CATCH Tutorial 01]] - Pollutant Export
:*[[TUFLOW_CATCH_Tutorial_M02 | TUFLOW CATCH Tutorial 02]] - Interventions
:*[[TUFLOW_CATCH_Tutorial_M03 | TUFLOW CATCH Tutorial 03]] - Hydrology
:*[[TUFLOW_CATCH_Tutorial_M04 | TUFLOW CATCH Tutorial 04]] - Integrated

== TUFLOW CATCH Documentation ==
TUFLOW CATCH documentation can be found in the TUFLOW CATCH Manual and the TUFLOW CATCH Changelog.

* [https://docs.tuflow.com/catch/manual/latest/ TUFLOW CATCH Manual]
* [https://docs.tuflow.com/catch/changelog/ TUFLOW CATCH Changelog]

=Contact=

For comments, requests and feedback contact [mailto:support@tuflow.com support@tuflow.com]. 
For further training opportunities see [https://tuflow.com/training/training-course-catalogue/ TUFLOW Training Catalogue] and/or contact [mailto:training@tuflow.com training@tuflow.com]. 
 

{{Tips Navigation
|uplink=[[Main_Page| Back to Wiki Main Page]]
}}

TUFLOW CATCH Tutorial M01 Project Initialisation QGIS

2026-06-02T00:00:29Z

Emilie Nielsen: undo rollback

== Introduction ==
QGIS is used to configure the TUFLOW CATCH project with the TUFLOW CATCH plugin. For installation, see [[TUFLOW_CATCH_Tutorial_Introduction#Software_Requirements | TUFLOW CATCH Tutorial Introduction]].

There are three steps to set up the TUFLOW CATCH project:
<ol>
<li>Define the QGIS Project Coordinate Reference System (CRS).
<li>Use the TUFLOW CATCH plugin to create the model folder structure and to write empty GIS files for model inputs.
<li>Set up the QGIS workspace to contain the DEM of the site.
</ol>

== Coordinate Reference System (CRS) ==
Define the CRS, also called 'Projection', for the QGIS workspace:
<ol>
<li> Open QGIS.
<li>Go to Project > Properties…
<li>In the CRS tab, type ‘WGS 84 / UTM Zone 60S’.
<li>Select the matching projection in the 'Predefined Coordinate Reference Systems' section.
<li>Click ‘Apply’ and ‘OK’.
<li>Ensure that the projection is set correctly by viewing the bottom right hand corner of the workspace. It should read ‘EPSG:32760’.
 
{{Video|name=animation_TC1_initialisation_01a.mp4|width=1236}} 
</ol>

== TUFLOW CATCH Plugin ==
Create the TUFLOW CATCH project:
<ol>
<li> Go to Processing > Toolbox from the top drop down menu options to open the Processing Toolbox.
<li> Go to TUFLOW Catch in the processing tool list and select 'Create TUFLOW Catch Project'. This opens the dialog shown below.
*Project Name: '''TC01'''
*Project Folder: Click '...', and navigate to the '''TUFLOW_CATCH_Module_01\Modelling''' folder.
*Project CRS: Click the drop down menu and select 'Project CRS: EPSG:32760 - WGS 84 / UTM zone 60S’.
*TUFLOW HPC Executable: Click '...', and navigate to the '''exe\TUFLOW\2026.0.0''' folder. Select '''TUFLOW_iSP_w64.exe'''.
*TUFLOW FV Executable: Click '...', and navigate to the '''exe\TUFLOWFV\2026.0.0''' folder. Select '''TUFLOWFV.exe'''.
*Default GIS Format: Click the drop down menu and select 'SHP'.
*Tick on 'Create Empty Files', 'Create Folder Structure' and 'Setup Control File Templates'
*Control File Templates: Expand the 'Advanced Parameters' section. Click '...', and tick on: TUFLOW CATCH Control file (.tcc), Batch file (.bat) and ESTRY Control file (.ecf). Ensure all other files are ticked off.

<li> Click 'Run' and a console window will open. This creates the TUFLOW CATCH folder structure, the projection files, the empty GIS files and template control files.
<li> Once the tool has finished, click 'Close'.
 
{{Video|name=animation_TC1_initialisation_02b.mp4|width=1236}} 
</ol>

The TUFLOW CATCH folder structure will now be set up in the '''TUFLOW_CATCH_Module_01\Modelling''' folder. The template files '''TC01_001.tcc''', '''Demonstration.bat''' and '''TC01_001.ecf''' will be in their respective folders. Note that the '''Modelling\TUFLOW''' folder still contains all files from [[Tutorial_M06#Part_3_-_Rainfall_Control_File | TUFLOW Tutorial Module 6 (part 3)]].

{{Video|name=animation_TC1_initialisation_03a.mp4|width=1236}} 

== QGIS Workspace ==
Set up the QGIS workspace to contain the model elevation data, and save the workspace:
<ol>
<li>In Windows File Explorer, navigate to the '''TUFLOW\model\grid''' folder. Drag and drop the '''DEM.tif''' file into QGIS.
<li>Change the symbology of the DEM:
* In the QGIS Layers panel, right click the '''DEM''' file and select 'Properties'.
*From the Symbology tab, under 'Band Rendering' select the following options:
:*Render type: Singleband pseudocolor
:*Color ramp: Spectral
:*Color ramp: Invert Color Ramp
:*Mode: Equal Interval
*From the Transparency tab, set the Global Opacity to 75%.
*Click 'Apply' and 'OK'.
 
{{Video|name=animation_TC1_initialisation_04a.mp4|width=1236}} 
<li>Create a hillshade of the DEM:
*Right click on the '''DEM''' file in the QGIS Layers Panel and select 'Duplicate Layer'.
*Right click on the '''DEM_copy''' and select 'Rename Layer'. Rename the layer to '''DEM_Hillshade'''.
*Right click on the '''DEM_Hillshade''' and select 'Properties'.
*From the Symbology tab, under 'Band Rendering' select the following options:
:*Render type: Hillshade
:*Z Factor: 3
*Click 'Apply' and 'OK'.
 
{{Video|name=animation_TC1_initialisation_05a.mp4|width=1236}} 
<li> Save the QGIS workspace:
*Go to Project > Save As.
*Navigate to the '''TUFLOW_CATCH_Module_01''' folder and save the workspace as '''TC01.qgz'''.
</ol>

 
{{Tips Navigation
|uplink=[[TUFLOW_CATCH_Tutorial_M01#Project_Initialisation| Back to TUFLOW CATCH Tutorial 1]]
}}

TUFLOW CATCH Tutorial M01 Project Initialisation QGIS

2026-06-01T23:59:14Z

Emilie Nielsen: Reverted edits by Emilie Nielsen (talk) to last revision by Abrar.Alttahir

== Introduction ==
QGIS is used to configure the TUFLOW CATCH project with the TUFLOW CATCH plugin. For installation, see [[TUFLOW_CATCH_Tutorial_Introduction#Software_Requirements | TUFLOW CATCH Tutorial Introduction]].

There are three steps to set up the TUFLOW CATCH project:
<ol>
<li>Define the QGIS Project Coordinate Reference System (CRS).
<li>Use the TUFLOW CATCH plugin to create the model folder structure and to write empty GIS files for model inputs.
<li>Set up the QGIS workspace to contain the DEM of the site.
</ol>

== Coordinate Reference System (CRS) ==
Define the CRS, also called 'Projection', for the QGIS workspace:
<ol>
<li> Open QGIS.
<li>Go to Project > Properties…
<li>In the CRS tab, type ‘WGS 84 / UTM Zone 60S’.
<li>Select the matching projection in the 'Predefined Coordinate Reference Systems' section.
<li>Click ‘Apply’ and ‘OK’.
<li>Ensure that the projection is set correctly by viewing the bottom right hand corner of the workspace. It should read ‘EPSG:32760’.
 
{{Video|name=video}} 
</ol>

== TUFLOW CATCH Plugin ==
Create the TUFLOW CATCH project:
<ol>
<li> Go to Processing > Toolbox from the top drop down menu options to open the Processing Toolbox.
<li> Go to TUFLOW Catch in the processing tool list and select create page 'Create TUFLOW Catch Project'. This opens the dialog shown below.
*Project Name: '''TC01'''
*Project Folder: Click '...', and navigate to the '''TUFLOW_CATCH_Module_01\Modelling''' folder.
*Project CRS: Click the drop down menu and select 'Project CRS: EPSG:32760 - WGS 84 / UTM zone 60S’.
*TUFLOW HPC Executable: Click '...', and navigate to the '''exe\TUFLOW\2025.0.3''' folder. Select '''TUFLOW_iSP_w64.exe'''.
*TUFLOW FV Executable: Click '...', and navigate to the '''exe\TUFLOWFV\2025.0.0''' folder. Select '''TUFLOWFV.exe'''.
*Default GIS Format: Click the drop down menu and select 'SHP'.
*Tick on 'Create Empty Files', 'Create Folder Structure' and 'Setup Control File Templates'
*Control File Templates: Click '...', and tick on: TUFLOW CATCH Control file (.tcc), Batch file (.bat) and ESTRY Control file (.ecf). Ensure all other files are ticked off.         → '''Suggestion:''' Consider mentioning that the Control File Templates can be viewed by expanding the ''Advanced Parameters'' section.

<li> Click 'Run' and a console window will open. This creates the TUFLOW CATCH folder structure, the projection files, the empty GIS files and template control files.
<li> Once the tool has finished, click 'Close'. 
 
[[File:image of tool dialog|link=Special:FilePath/Image_of_tool_dialog]] 
 
</ol>

The TUFLOW CATCH folder structure will now be set up in the '''TUFLOW_CATCH_Module_01\Modelling''' folder. The template files '''TC01_001.tcc''', '''Demonstration.bat''' and '''TC01_001.ecf''' will be in their respective folders. Note that the '''Modelling\TUFLOW''' folder still contains all files from TUFLOW Tutorial Module 6 (part 3).

'''Suggestion:''' Consider adding hyperlinks for all mentions of TUFLOW Tutorial Module 6 (part 3). 
{{Video|name=video showing tool output}} 

== QGIS Workspace ==
Set up the QGIS workspace to contain the model elevation data, and save the workspace:
<ol>
<li>In Windows File Explorer, navigate to the '''TUFLOW\model\grid''' folder. Drag and drop the '''DEM.tif''' file into QGIS.
<li>Change the symbology of the DEM:
* In the QGIS Layers panel, right click the '''DEM''' file and select 'Properties'.
*From the Symbology tab, under 'Band Rendering' select the following options:
:*Render type: Singleband pseudocolor
:*Color ramp: Spectral
:*Color ramp: Invert Color Ramp
:*Mode: Equal Interval
*From the Transparency tab, set the Global Opacity to 75%.
*Click 'Apply' and 'OK'.
 
{{Video|name=}} 
<li>Create a hillshade of the DEM:
*Right click on the '''DEM''' file in the QGIS Layers Panel and select 'Duplicate Layer'.
*Right click on the '''DEM_copy''' and select 'Rename Layer'. Rename the layer to '''DEM_Hillshade'''.
*Right click on the '''DEM_Hillshade''' and select 'Properties'.
*From the Symbology tab, under 'Band Rendering' select the following options:
:*Render type: Hillshade
:*Z Factor: 3
*Click 'Apply' and 'OK'.
 
{{Video|name=video}} 
<li> Save the QGIS workspace:
*Go to Project > Save As.
*Navigate to the '''TUFLOW_CATCH_Module_01''' folder and save the workspace as '''CATCH_M01.qgz'''.
</ol>

 
{{Tips Navigation
|uplink=[[TUFLOW_CATCH_Tutorial_M01#Project_Initialisation| Back to TUFLOW CATCH Tutorial 1]]
}}

TUFLOW CATCH Tutorial M01 Project Initialisation QGIS

2026-06-01T23:58:48Z

Emilie Nielsen: /* Introduction */

== Introduction ==
QGIS is used to configure the TUFLOW CATCH project with the TUFLOW plugin. For installation, see [[TUFLOW_CATCH_Tutorial_Introduction#Software_Requirements | TUFLOW CATCH Tutorial Introduction]].

There are three steps to set up the TUFLOW CATCH project:
<ol>
<li>Define the QGIS Project Coordinate Reference System (CRS).
<li>Use the TUFLOW CATCH plugin to create the model folder structure and to write empty GIS files for model inputs.
<li>Set up the QGIS workspace to contain the DEM of the site.
</ol>

== Coordinate Reference System (CRS) ==
Define the CRS, also called 'Projection', for the QGIS workspace:
<ol>
<li> Open QGIS.
<li>Go to Project > Properties…
<li>In the CRS tab, type ‘WGS 84 / UTM Zone 60S’.
<li>Select the matching projection in the 'Predefined Coordinate Reference Systems' section.
<li>Click ‘Apply’ and ‘OK’.
<li>Ensure that the projection is set correctly by viewing the bottom right hand corner of the workspace. It should read ‘EPSG:32760’.
 
{{Video|name=animation_TC1_initialisation_01a.mp4|width=1236}} 
</ol>

== TUFLOW CATCH Plugin ==
Create the TUFLOW CATCH project:
<ol>
<li> Go to Processing > Toolbox from the top drop down menu options to open the Processing Toolbox.
<li> Go to TUFLOW Catch in the processing tool list and select 'Create TUFLOW Catch Project'. This opens the dialog shown below.
*Project Name: '''TC01'''
*Project Folder: Click '...', and navigate to the '''TUFLOW_CATCH_Module_01\Modelling''' folder.
*Project CRS: Click the drop down menu and select 'Project CRS: EPSG:32760 - WGS 84 / UTM zone 60S’.
*TUFLOW HPC Executable: Click '...', and navigate to the '''exe\TUFLOW\2026.0.0''' folder. Select '''TUFLOW_iSP_w64.exe'''.
*TUFLOW FV Executable: Click '...', and navigate to the '''exe\TUFLOWFV\2026.0.0''' folder. Select '''TUFLOWFV.exe'''.
*Default GIS Format: Click the drop down menu and select 'SHP'.
*Tick on 'Create Empty Files', 'Create Folder Structure' and 'Setup Control File Templates'
*Control File Templates: Expand the 'Advanced Parameters' section. Click '...', and tick on: TUFLOW CATCH Control file (.tcc), Batch file (.bat) and ESTRY Control file (.ecf). Ensure all other files are ticked off.

<li> Click 'Run' and a console window will open. This creates the TUFLOW CATCH folder structure, the projection files, the empty GIS files and template control files.
<li> Once the tool has finished, click 'Close'.
 
{{Video|name=animation_TC1_initialisation_02b.mp4|width=1236}} 
</ol>

The TUFLOW CATCH folder structure will now be set up in the '''TUFLOW_CATCH_Module_01\Modelling''' folder. The template files '''TC01_001.tcc''', '''Demonstration.bat''' and '''TC01_001.ecf''' will be in their respective folders. Note that the '''Modelling\TUFLOW''' folder still contains all files from [[Tutorial_M06#Part_3_-_Rainfall_Control_File | TUFLOW Tutorial Module 6 (part 3)]].

{{Video|name=animation_TC1_initialisation_03a.mp4|width=1236}} 

== QGIS Workspace ==
Set up the QGIS workspace to contain the model elevation data, and save the workspace:
<ol>
<li>In Windows File Explorer, navigate to the '''TUFLOW\model\grid''' folder. Drag and drop the '''DEM.tif''' file into QGIS.
<li>Change the symbology of the DEM:
* In the QGIS Layers panel, right click the '''DEM''' file and select 'Properties'.
*From the Symbology tab, under 'Band Rendering' select the following options:
:*Render type: Singleband pseudocolor
:*Color ramp: Spectral
:*Color ramp: Invert Color Ramp
:*Mode: Equal Interval
*From the Transparency tab, set the Global Opacity to 75%.
*Click 'Apply' and 'OK'.
 
{{Video|name=animation_TC1_initialisation_04a.mp4|width=1236}} 
<li>Create a hillshade of the DEM:
*Right click on the '''DEM''' file in the QGIS Layers Panel and select 'Duplicate Layer'.
*Right click on the '''DEM_copy''' and select 'Rename Layer'. Rename the layer to '''DEM_Hillshade'''.
*Right click on the '''DEM_Hillshade''' and select 'Properties'.
*From the Symbology tab, under 'Band Rendering' select the following options:
:*Render type: Hillshade
:*Z Factor: 3
*Click 'Apply' and 'OK'.
 
{{Video|name=animation_TC1_initialisation_05a.mp4|width=1236}} 
<li> Save the QGIS workspace:
*Go to Project > Save As.
*Navigate to the '''TUFLOW_CATCH_Module_01''' folder and save the workspace as '''TC01.qgz'''.
</ol>

 
{{Tips Navigation
|uplink=[[TUFLOW_CATCH_Tutorial_M01#Project_Initialisation| Back to TUFLOW CATCH Tutorial 1]]
}}

TUFLOW CATCH Tutorial M01

2026-06-01T23:58:25Z

Emilie Nielsen: /* Project Initialisation */

= Introduction =
In this module, a TUFLOW CATCH pollutant export model is developed. 

TUFLOW CATCH Tutorial 01 is built from the model created in [[Tutorial_M06#Part_3_-_Rainfall_Control_File | TUFLOW Tutorial Module 6 - Part 3]]. The completed TUFLOW Module 6 (part 3) is provided in the '''TUFLOW_CATCH_Module_01\Modelling\TUFLOW''' folder of the download dataset as the starting point for this tutorial. If unfamiliar with TUFLOW, it is recommended to complete Modules 1, 2, 3 and 6 of the [[Tutorial_Introduction | TUFLOW Tutorials]] to establish an understanding of 1D and 2D TUFLOW modelling, including direct rainfall models.

= Project Initialisation =
TUFLOW CATCH models are separated into a series of folders which contain the input and output files. The recommended directory structure for TUFLOW CATCH models consists of a top-level folder, '''Modelling''', which contains three subfolders:
* '''TUFLOW''': Contains TUFLOW HPC input files.
* '''TUFLOWCATCH''': Contains the TUFLOW CATCH Control file, as well as all check, results and log files.
* '''TUFLOWFV''': Contains TUFLOW FV input files.
The third level subfolders are outlined below. For a more detailed description, refer to the [https://docs.tuflow.com/catch/latest/ TUFLOW CATCH Manual]. For more information on TUFLOW HPC or TUFLOW FV folder structures, refer to the [https://docs.tuflow.com/classic-hpc/manual/latest/ TUFLOW Manual] or the [https://downloads.tuflow.com/TUFLOWFV/Releases/Latest/TUFLOW_FV_User_Manual.pdf TUFLOW FV Manual]. 
<ol>
[[File:TC1_folder_structure_01a.png|left]]
{| class="wikitable"

! style="background-color:#005581; font-weight:bold; color:white;" | Folder
! style="background-color:#005581; font-weight:bold; color:white;" width=10%| Sub-Folder (s)
! style="background-color:#005581; font-weight:bold; color:white;" width=75%| Description
|-
|rowspan="3" style="text-align: center;"|TUFLOW
| bc_dbase model|| Follows standard TUFLOW structure.
|-
| catch || Not used, but generated for internal use. It holds files that are produced during computation, but deleted when the simulation finishes successfully.
|-
| check results runs || Not used, but generated for internal use. All TUFLOW check and results files are written to the '''TUFLOWCATCH\check''' folder and the '''TUFLOWCATCH\results''' folder respectively. TUFLOW CATCH simulations are run from the .tcc file in the '''TUFLOWCATCH\runs''' folder.
|-
|rowspan="6" style="text-align: center;"|TUFLOWCATCH
| bc_dbase|| Contains the output boundary condition and time-series data.
|-
| check || Contains the GIS and other check files produced by TUFLOW CATCH, TUFLOW and TUFLOW FV to carry out quality control checks
|-
| model || Not used - generated for internal use.
|-
| results|| Contains the result files produced by TUFLOW CATCH, TUFLOW and TUFLOW FV.
|-
| runs|| Contains the .tcc simulation control file.
|-
| runs\log || Contains the log files (e.g. .catchlog, .tlf, .log, etc) and _messages.shp files produced by TUFLOW CATCH, TUFLOW and TUFLOW FV.
|-
|rowspan="2" style="text-align: center;"|TUFLOWFV
| bc_dbase model stm wqm|| Follows standard TUFLOW FV structure.
|-
| check results runs || Not used, but generated for internal use. All TUFLOW FV check and results files are written to the '''TUFLOWCATCH\check''' folder and the '''TUFLOWCATCH\results''' folder respectively. TUFLOW CATCH simulations are run from the .tcc file in the '''TUFLOWCATCH\runs''' folder.
|}
</ol>

The TUFLOW CATCH folders can be set up manually, or automatically through the TUFLOW QGIS Plugin (recommended).
:*[[TUFLOW_CATCH_Tutorial_M01_Project_Initialisation_QGIS | TUFLOW CATCH Project Initialisation]]

= GIS Inputs =
Create, import and view input data:
:*[[TUFLOW_CATCH_Tutorial_M01_GIS_Inputs_QGIS | TC01 - GIS Inputs]]

= TUFLOW Boundary Condition Database (bc_dbase) =
Update the bc_dbase to remove the 2D boundaries and add a reference to the timeseries temperature data. Note that TUFLOW CATCH does not support 2D boundaries, however, 2d_sa GIS layers can be used to simulate non-hydrologic surface loads. For more information on 2d_sa inputs, refer to [https://docs.tuflow.com/catch/manual/2025.2/ProcessDescriptionsSAs-2.html#ProcessDescriptionsSAs-2 Section 3.4 of the TUFLOW CATCH Manual].
<ol>
<li>In Windows File Explorer, navigate to the '''TUFLOW_CATCH_Module_01\Tutorial_Data''' folder. Copy the '''temperature.csv''' and paste it in the '''TUFLOW_CATCH_Module_01\Modelling\TUFLOW\bc_dbase''' folder. This file contains the timeseries temperature data.
<li> Open the file. As this file will be read by TUFLOW CATCH, the first column must contain the date in ISODATE format (DD/MM/YYYY hh:mm:ss). It will also be read by TUFLOW HPC, and therefore must have a column specifying a time in hours from the beginning of the model. In this case, the 'TUFLOW_Time' column contains the time in hours. For example, 01/01/2021 10:00:00 corresponds to 0, 01/01/2021 11:00:00 to 1, and so on. 
 
[[File: TC1_temperature_csv_01a.png]] 
 
<li> In the '''TUFLOW\bc_dbase''' folder, save a copy of the '''bc_dbase_M06_001.csv''' as '''bc_dbase_TC01_001.csv'''.
<li> Open the file and remove the references to the 2D boundaries (FC01, FC02, FC04, FC05, FC06 and FC07).
<li> Add the reference to the timeseries temperature data as shown below: 
 
[[File: TC1_bc_dbase_01b.png]] 
 
<li> Save the bc_dbase.
</ol>

= Materials =
Surface roughness or bed resistance values (e.g. Manning’s n) are assigned to material IDs. To simulate a more complex catchment area, more material IDs have been specified.
<ol>
<li>In Windows File Explorer, navigate to the '''TUFLOW_CATCH_Module_01\Tutorial_Data''' folder. Copy the '''materials_TC01_001.csv''' and paste it in the '''TUFLOW_CATCH_Module_01\Modelling\TUFLOW\model''' folder. This file is a modified version of '''materials_M06_002.csv''' from [[Tutorial_M06#Materials_2 | TUFLOW Tutorial Module 6]].
<li>Open the file. Roughness values (Manning's n) have been applied to the five new material IDs: 
 
[[File: TC1_materials_01b.png]] 
 
<li>These new material IDs have been assigned to allow different pollutant export properties to be specified to each material ID. This is discussed in the [[#Pollutant_Export_Model | TUFLOW CATCH Control File]] section.
</ol>

= TUFLOW Soil File (.tsoilf) =
The soils (.tsoilf) file is similar to the materials file. A positive integer ID is assigned to each soil, then an infiltration method followed by the soil parameters. For this tutorial, there is only one soil type (ID 1) which is applied across the whole model.
<ol>
<li>In Windows File Explorer, navigate to the '''TUFLOW_CATCH_Module_01\Tutorial_Data''' folder. Copy the '''TC01_soils_001.tsoilf''' and paste it in the '''TUFLOW_CATCH_Module_01\Modelling\TUFLOW\model''' folder. 
<li>Open the file. The Green-Ampt (GA) infiltration method has been used. For more information on infiltration methods, refer to the [https://docs.tuflow.com/classic-hpc/manual/latest/ TUFLOW Manual]. 
 
[[File: TC1_soils_file_01a.png]] 
 
</ol>

= Simulation Control Files =
The following steps will require use of a text editor. The tutorial demonstration uses Notepad++. For its configuration information refer to [[NotepadPlusPlus_Tips | Notepad++ Tips]]. 
=== TUFLOW Geometry Control File (TGC) ===
<ol>
<li> Save a copy of '''M02_001.tgc''' as '''TC01_001.tgc''' in the '''TUFLOW_CATCH_Module_01\Modelling\TUFLOW\model''' folder.
<li> Open the '''TC01_001.tgc''' in a text editor and add the following line after the '<tt>Read GIS Mat</tt>' command to reference the new materials GIS layer. 
<tt>Read GIS Mat == gis\2d_mat_TC01_001_R.shp ! Sets material values according to attributes in the GIS layer</tt> 
<li> Add the following section to globally set the soil ID and the soil thickness: 
<tt>! SOILS</tt> 
<tt>Set Soil == 1 ! Globally sets the soil ID to 1</tt> 
<tt>Set Soil Thickness == 0.2 ! Globally sets the soil thickness to 0.2m</tt> 
<li> Save the TGC.
</ol>

=== TUFLOW Boundary Control File (TBC) ===
<ol>
<li>Save a copy of '''M06_003.tbc''' as '''TC01_001.tbc''' in the '''TUFLOW_CATCH_Module_01\Modelling\TUFLOW\model''' folder.
<li> Open the '''TC01_001.tbc''' in a text editor and remove or comment out the reference to the 2D boundaries using a '<tt>!</tt>' symbol. 
<tt>! Read GIS BC == gis\2d_bc_M01_001_L.shp ! Reads in downstream 2D boundary</tt> 
<li> Add the additional lines to reference the 1D/2D culvert connections: 
<tt>Read GIS BC </tt> <tt>== </tt> <tt>gis\2d_bc_M03_culverts_001_P.shp</tt> <tt> ! Links the 1D culverts to the 2D domain</tt> 
<tt>Read GIS BC </tt> <tt>== </tt> <tt>gis\2d_bc_M03_culverts_001_R.shp | gis\2d_bc_M03_culverts_001_L.shp</tt> <tt> ! Links the 1D culverts to the 2D domain</tt> 
<li>Save the TBC.
</ol>

=== TUFLOW ESTRY Control File (ECF) ===
<ol>
<li> Navigate to the '''TUFLOW_CATCH_Module_01\Modelling\TUFLOW\model''' folder, and open '''TC01_001.ecf''' in a text editor. This file was created using the TUFLOW CATCH plugin.
<li> In the '1D Time Control' section, ensure the following command has been specified to set the 1D computational timestep: 
<tt>Timestep </tt> <tt>== </tt> <tt>0.5</tt> <tt> ! Specifies a 1D computational timestep of 0.5 seconds</tt> 
<li> In the '1D Elements' section, add the following command to define the culverts: 
<tt>Read GIS Network </tt> <tt>== </tt> <tt>gis\1d_nwk_M03_culverts_001_L.shp</tt> <tt> ! Defines culverts</tt>
<li> Add the following command line to define the Advection Dispersion (AD) approach. For more information on Advection Dispersion, please refer to the [https://docs.tuflow.com/classic-hpc/manual/latest/ TUFLOW Manual]. 
<tt>AD Approach == METHOD A ! Sets the modelling approach for the Advection Dispersion through 1D channels</tt>
<li>Save the ECF.
</ol>

== TUFLOW CATCH Control File (TCC) ==
A TUFLOW CATCH simulation is set up and executed by constructing a TUFLOW CATCH Control file (.tcc). TUFLOW Control file (.tcf) and TUFLOW FV Control file (.fvc) are not used. The .tcc has four command blocks:
<ol>
<li> Global settings
<li> Catchment Hydraulic Model (TUFLOW HPC) commands
<li> Catchment Pollutant Export Model
<li> Receiving Model (TUFLOW FV) commands
</ol>
All blocks must be included in the above order, but the later three can be switched on and off with a single command.

The TUFLOW CATCH plugin has created a .tcc template file in the '''TUFLOWCATCH\runs''' folder, '''TC01_001.tcc'''. This file has been populated with all the commands needed to execute a TUFLOW CATCH simulation. In this section, the template commands will be populated/updated for this tutorial model.

=== Global Settings ===
This section contains information that is applied equally to both TUFLOW HPC and TUFLOW FV.
<ol>
<li> Navigate to the '''TUFLOW_CATCH_Module_01\Modelling\TUFLOWCATCH\runs''' folder and open '''TC01_001.tcc''' into a text editor.
<li> In the 'Simulation Settings' section, update the time commands: 
<tt>Start Time == 01/01/2021 10:00:00 ! Specifies the simulation start time</tt> 
<tt>End Time == 01/01/2021 13:00:00 ! Specifies the simulation end time</tt> 
<li> In the 'Boundary Condition Configuration' section, update the BC and CSV output intervals: 
<tt>Catch BC Output Interval Nodestring == 300 ! Outputs BC nodestring data every 300 seconds</tt> 
<tt>Catch BC Output Interval Lateral == 300 ! Outputs BC lateral data every 300 seconds</tt> 
<tt>CSV Write Frequency Day == 0.01 ! Writes CSV output every 0.01 days</tt> 
</ol>

=== Catchment Hydraulic Model (TUFLOW HPC) ===
This block contains commands that construct the TUFLOW HPC simulation. These commands are almost entirely those that would be used in setting up a standalone TUFLOW HPC control file (.tcf), with a small number of additional commands that relate to TUFLOW CATCH.
<ol>
<li> Set the catchment hydraulic model: 
<tt>Catchment Hydraulic Model == HPC </tt>

<li> Set the zero date. TUFLOW HPC does not support ISODATE format, while TUFLOW FV requires it. This command ensures compatibility by setting the date in TUFLOW FV ISODATE format that corresponds to zero hours in TUFLOW HPC boundary condition files. 
<tt>Zero Date == 01/01/2021 10:00 ! Specifies the simulation start time in TUFLOW FV ISODATE format</tt> 

<li> In the 'GIS' section, remove or comment out the following command using a '<tt>!</tt>' symbol. The SHP projection has already been set in the [[#Global_Settings |Global Settings]] section. 
<tt>! SHP Projection == ..\..\TUFLOW\model\gis\projection.shp</tt> 

<li> In the 'GIS' section, set the projection for the output grid files: 
<tt>TIF Projection == ..\..\TUFLOW\model\grid\DEM.tif ! Sets the GIS projection for the output grid files</tt> 

<li> In the 'Solver' section, set the timestep maximum and time format: 
<tt>Timestep Maximum == 2.5 ! Specifies a maximum timestep (seconds)</tt> 
<tt>Time Format == TUFLOWFV ! Specifies the time format of output results</tt> 

<li> In the 'SGS' section, set the sample target distance: 
<tt>SGS Sample Target Distance == 0.5 ! Sets SGS Sample Target Distance (meters)</tt> 

<li> In the 'Control Files' section, ensure all control files are referenced. 
<tt>Geometry Control File == ..\..\TUFLOW\model\TC01_001.tgc ! Reference the TUFLOW Geometry Control File</tt> 
<tt>BC Control File == ..\..\TUFLOW\model\TC01_001.tbc ! Reference the TUFLOW Boundary Conditions Control File</tt> 
<tt>BC Database == ..\..\TUFLOW\bc_dbase\bc_dbase_TC01_001.csv ! Reference the Boundary Conditions Database</tt> 
<tt>Read Materials File == ..\..\TUFLOW\model\materials_TC01_001.csv ! Reference the Materials Definition File</tt> 
<tt>Rainfall Control File == ..\..\TUFLOW\model\M06_point2grid_003.trfc ! Reference the TUFLOW Rainfall Control File</tt> 
<tt>ESTRY Control File == ..\..\TUFLOW\model\TC01_001.ecf ! Reference the ESTRY (1D) Control File</tt> 

<li> In the 'Soils' section, reference the soils file (.tsoilf), and remove or comment out the 'soil negative rainfall approach' command using a '<tt>!</tt>' symbol. 
<tt>Read Soils File == ..\..\TUFLOW\model\TC01_soils_001.tsoilf ! Reference the Soils File</tt> 
<tt>! Soil Negative Rainfall Approach == FACTOR</tt> 

<li> In the 'Pollutant Configuration' section, reference the receiving polygon and set the pollutants. In this tutorial, salinity, temperature, dissolved oxygen (WQ_DISS_OXYGEN_MG_L), alive and dead ecoli (WQ_PATH_ECOLI_ALIVE/DEAD_CFU_100ML) and clay sediment (SED_CLAY) are simulated. 
<tt>Receiving Polygon == ..\..\TUFLOW\model\gis\2d_rp_TC01_001_R.shp ! GIS layer defining the receiving polygon</tt> 
<tt>Pollutant == Salinity, Temperature, WQ_DISS_OXYGEN_MG_L, WQ_PATH_ECOLI_ALIVE_CFU_100ML, WQ_PATH_ECOLI_DEAD_CFU_100ML, SED_CLAY ! Specify the pollutant names </tt> 

<li> In the 'Output Map Configuration' section, update the following commands to set the map output formats, the map output interval, map cuttoff depth and to define the TIF output parameters. 
<tt>Map Output Format == XMDF TIF ! Result file types</tt> 
<tt>Map Output Data Types == catch h v d ! Output data types</tt> 
<tt>Map Output Interval == 30 ! Interval of output map data (seconds)</tt> 
<tt>Map Cutoff Depth == 0.05 ! Sets map cutoff depth (meters)</tt> 
<tt>TIF Map Output Interval == 0 ! Interval of output TIF map data (seconds)</tt> 
<tt>TIF Map Output Data Types == h d dt ! TIF result file types</tt> 
</ol>

===Pollutant Export Model===
This block contains commands that control the pollutant export (and other constituent) simulation.
<ol>
<li> Set the pollutant export model: 
<tt>Catchment Pollutant Export Model == Mass Accumulation Release </tt>

<li> In the 'Constant Concentrations' section, add the following commands. They set the pollutants 'Salinity' and 'WQ_DISS_OXYGEN_MG_L' (dissolved oxygen) to a constant concentration value that is applied equally to all boundaries and summary files where appropriate. 
<tt>Constant Salinity == 0.0 ! Specify the constant concentration of salinity</tt> 
<tt>Constant WQ_DISS_OXYGEN_MG_L == 8.0 ! Specify the constant concentration of dissolved oxygen</tt> 

<li> In the 'Time Series' section, add the following command. It sets the pollutant 'Temperature' to be a time-series input, and points to the name 'temp' in the bc_dbase. 
<tt>Time-Series Temperature == temp ! Specify temperature as a timeseries and the corresponding BC database name</tt> 

<li>In the 'Pollutant Export Properties' section, add the material block '<tt>ALL</tt>' (<tt>Material == ALL</tt>) from the page linked below. This code block defines the default pollutant export properties for each pollutant. Once uniform conditions are set, progressive specifications of material by material pollutant behaviour can be set. These specifications override previous settings on a spatial basis. Including the default (<tt>ALL</tt>) material block is considered best practice, as it ensures that all pollutants have export properties defined across the entire TUFLOW HPC domain, otherwise an error will occur. For more information on the pollutant export parameters, refer to [https://docs.tuflow.com/catch/manual/2025.0/SimulationConstruction-1.html#SCTCCPollExpPE-4 Section 4.5.3.3 of the TUFLOW CATCH Manual].
:*[[TUFLOW_CATCH_Tutorial_M01_Pollutant_Export#Default_.28ALL.29 | Pollutant Export Properties: ALL]] 

<li>To set the pollutant export properties for the different material IDs, blocks similar to the above (e.g. <tt>Material == 4</tt>) can be used. The material IDs correspond to those defined in the '''2d_mat_TC01_001.shp''' and '''2d_mat_M01_001.shp''' GIS layers. 
 
To estimate E. coli export rates for each paddock, the area of each paddock was calculated. Based on this, appropriate animal populations were assigned. Using these values, the E. coli rates were calculated. For more information on pollutant export calculations, refer to [https://docs.tuflow.com/catch/manual/2025.0/ProcessDescriptions-1.html#ProcessDescriptionsMats-3 Section 3.2.3 of the TUFLOW CATCH Manual]. 
 
[[File: TC1_aerial_with_paddocks_01a.png|left]]
 
{| class="wikitable"

! style="background-color:#005581; font-weight:bold; color:white; padding: 10px" |Material ID
! style="background-color:#005581; font-weight:bold; color:white; padding: 10px" |Paddock Name
! style="background-color:#005581; font-weight:bold; color:white; padding: 10px" |Area (ha)
! style="background-color:#005581; font-weight:bold; color:white; padding: 10px" |Animals
|-
|6||paddockA||1.5|| 23 Sheep, 7 Lambs
|-
|7||paddockB||0.3||2 Cows
|-
|8||paddockC||1.2||20 Sheep
|-
|9||paddockD || 1||4 Cows, 2 Calves
|}
 
 

<li> Set the pollutant export properties for material ID 1. This is the material ID for all areas within the model domain not covered by a material region. These pollutant export properties define the release and deposition of clay sediment. Sediment pollutants generally use the 'Shear1' method. For more information on 'Shear1', refer to [https://docs.tuflow.com/catch/manual/2025.0/SimulationConstruction-1.html#SCTCCPollExpSS-5 Section 4.5.3.3.2 of the TUFLOW CATCH Manual]. 
:*[[TUFLOW_CATCH_Tutorial_M01_Pollutant_Export#Model_Area_.281.29 | Pollutant Export Properties: 1]]

<li>Set the pollutant export properties for material ID 4 (waterholes, eddies, etc). These properties define settling (deposition velocity) of alive and dead E. coli to 2 meters per day (approx 25cm during the simulation). 
:*[[TUFLOW_CATCH_Tutorial_M01_Pollutant_Export#Slow_Moving_Water_.284.29 | Pollutant Export Properties: 4]]

<li>Set the pollutant export properties for material ID's 6 (paddockA), 7 (paddockB), 8 (paddockC) and 9 (paddockD). These properties define the accumulation (rate) and washoff of alive and dead E. coli for the animals on the paddock. 
:*[[TUFLOW_CATCH_Tutorial_M01_Pollutant_Export#Paddocks_.286.2C_7.2C_8_and_9.29 | Pollutant Export Properties: 6, 7, 8, 9]]

<li> For this tutorial, leave all interventions commands as is. This section of the .tcc will be discussed in [[TUFLOW_CATCH_Tutorial_M02 |TUFLOW CATCH Tutorial 02]].
<li> Save the .tcc.
</ol>

===Receiving Model (TUFLOW FV)===
For this tutorial, leave all commands as is. This section of the .tcc will be populated in [[TUFLOW_CATCH_Tutorial_M03 | TUFLOW CATCH Tutorial 03]].

=Running the Simulation=
<ol>
<li>In Windows File Explorer, navigate to the '''TUFLOWCATCH\runs''' folder. The TUFLOW CATCH plugin created a batch file (.bat) that references the .tcc called '''Demonstration.bat'''.
<li>Save a copy of '''Demonstration.bat''' as '''_run_TC01_CATCH.bat''' and open the file in a text editor.
<li>Update the batch file to reference the TUFLOW CATCH executable: 
<tt>set exe="..\..\..\..\exe\TUFLOWCATCH\2026.0.0\TUFLOWCATCH.exe"</tt> 
<tt>%exe% TC01_001.tcc</tt>
<li>Double click the batch file in file explorer to run the simulation.
</ol>

=Troubleshooting=
See tips on common mistakes and troubleshooting steps if the model doesn't run:
:*[[Tutorial_Troubleshooting_QGIS | QGIS]]

=Check Files and Results Output=
Complete the steps outlined in the following links to review check files and simulation results from the TUFLOW CATCH pollutant export model simulation:
:*[[TUFLOW_CATCH_Tutorial_M01_Check_Files_QGIS | TC01 - Check Files]] 
:*[[TUFLOW_CATCH_Tutorial_M01_Results_QGIS | TC01 - Results]] 

=Reviewing Model Performance=
There are a number of useful outputs from TUFLOW CATCH for reviewing the model performance.

===TUFLOW CATCH Log File (.catchlog)===
The first file to review is the TUFLOW CATCH Log File (.catchlog). The <tt>Log Folder == log</tt> command in the .tcc controls where the .catchlog is written. 
Navigate to the '''Modelling\TUFLOWCATCH\runs\log''' folder and open the '''TC01_001.catchlog''' file in a text editor. It contains a summary of the TUFLOW CATCH simulation. The following are the key points to review: 
* '''Global Settings:''' The commands from the 'Global Settings' section of the .tcc are echoed here. Review these to confirm that the correct settings have been applied. 
:[[File: TC1_catchlog_01b.png]] 
* '''Simulation Configuration:''' The .catchlog outlines which models have been used and what simulation configuration has been run. In this tutorial, the catchment hydraulic and pollutant export models have been applied, indicating a pollutant export configuration. 
:[[File: TC1_catchlog_02a.png]] 
* '''Run Status:''' At the end of the file, a message will confirm the simulation outcome.
:* If successful, it will state 'Run Successful' 
::[[File: TC1_catchlog_03b.png]] 
:* If an issue occurred, the simulation will stop and an error message will be reported. An example error is shown in the image below.
::'''Note:''' Each TUFLOW CATCH error message has a corresponding wiki page that provides further details about the error, and suggestions for how to fix the issue. Refer to [[5xxx_TUFLOW_Messages | 5xxx Messages]] for a list of all TUFLOW CATCH related error messages. 
::[[File: TC1_catchlog_04c.png]] 

===Other Log Files===
Once the .catchlog has been reviewed, it is recommended to check the TUFLOW Log File (.tlf) if the catchment hydraulic model has been specified and to check the TUFLOW FV Log File (.log) if the receiving model has been specified. These files contain TUFLOW and TUFLOW FV specific check, warning and error messages.

====TUFLOW Log File (.tlf)====
Since the catchment hydraulic model is specified in this tutorial, review the TUFLOW Log File. The <tt>Log Folder == log</tt> command in the .tcc defines where the .tlf is written 
Navigate to the '''Modelling\TUFLOWCATCH\runs\log''' folder and open the '''TC01_001_catchment_hydraulic.tlf''' file in a text editor.
* Scroll down to the bottom to 'Simulation Summary'. This includes information about the computation time, messages, volume calculations and mass error.
* Review any check, warning or error messages.
* For more information on reviewing TUFLOW log outputs, refer to [[HPC_Model_Review | HPC Model Review]].

====TUFLOW FV Log File (.log)====
The receiving model has not been specified in this tutorial, so no TUFLOW FV Log File (.log) has been created. The TUFLOW FV Log File will be reviewed in [[TUFLOW_CATCH_Tutorial_M03#Reviewing_Model_Performance | TUFLOW CATCH Tutorial 03]].

=Conclusion=
* A TUFLOW CATCH Pollutant Export model was created. A downstream receiving polygon was used to track pollutants in the receiving waters.
* Check files were used to review the transfer from the Catchment Hydraulic model (TUFLOW HPC) into the receiving polygon.
* TUFLOW CATCH time series results and TUFLOW map outputs were assessed to observe the pollutant behaviours.
* For further training opportunities see [https://tuflow.com/training/training-course-catalogue/ TUFLOW Training Catalogue] and/or contact [mailto:training@tuflow.com training@tuflow.com]. 
 
{{Tips Navigation
|uplink=[[TUFLOW_CATCH_Tutorial_Introduction| Back to Tutorial Introduction Main Page]]
}}

TUFLOW CATCH Tutorial Introduction

2026-06-01T23:56:01Z

Emilie Nielsen: /* Software Requirements */

= Introduction =
The following tutorial models are aimed at new and experienced users, stepping through the process of building and running TUFLOW CATCH together. These tutorials aim to demonstrate the power and flexibility of TUFLOW CATCH in simulating catchment-wide hydrologic, hydraulic, pollutant export, and receiving waterway processes. TUFLOW CATCH enables detailed simulation of surface and subsurface flows, pollutant transport, and downstream environmental impact without relying on lumped or average assumptions.

'''Note: Users new to TUFLOW are encouraged to first complete Module 1, 2, 3 and 6 of the [[Tutorial_Introduction | TUFLOW Tutorials]]. These modules cover key concepts in 1D and 2D modeling, as well as direct rainfall models.'''

=Software Requirements=
TUFLOW uses QGIS as its Graphical User Interface (GUI), in combination with text editor and spreadsheet software, for its model creation and result viewing. The group of software creates an extremely workflow efficient and flexible modeling environment. Notably, QGIS does not experience the data load/visualization lag and display issues some other hydraulic modeling software GUI's are limited by when working with larger datasets. 

{| class="wikitable" width="75%"

! style="background-color:#005581; font-weight:bold; color:white;"| Requirement
! style="background-color:#005581; font-weight:bold; color:white;" | Brief Description
! style="background-color:#005581; font-weight:bold; color:white;" | Download
|-
| '''TUFLOW''' || TUFLOW is a computer program for simulating depth-averaged, one and two-dimensional free-surface flows such as occurs from floods and tides, with the 2D solution occurring over a regular grid or quadtree mesh of square elements. 
It is recommended to always use the latest release version of TUFLOW. 

This tutorial model does not require a TUFLOW license. 

This tutorial is configured to use a NVIDIA GPU card. If this is not available, the simulations can be run on CPU using the <tt>Hardware == CPU</tt> command.
||The TUFLOW executable is provided within the [[TUFLOW_CATCH_Tutorial_Introduction#Tutorial_Data | Tutorial Download Dataset]].
|-
| '''QGIS''' QGIS TUFLOW plugin || QGIS is the Geographic Information System (GIS) Graphical User Interface (GUI) used to build models and view results.

The QGIS TUFLOW plugin includes numerous tools to increase workflow efficiency.

||[https://qgis.org/download/ Latest 64-bit version of QGIS]. 

[[TUFLOW_QGIS_Plugin| QGIS TUFLOW Plugin Installation]].
|-
| '''NotePad++''' Syntax Highlighting || A text editor is required for creation of the TUFLOW control (script) files. This tutorial was developed with NotePad++. Ideally a text editor should be able to: 
*Color code the TUFLOW control files;
*Open other files from the active control file; and
*Launch a TUFLOW simulation. 
TUFLOW color coding can be enabled using syntax highlighting.
|| [https://notepad-plus-plus.org/downloads/ Latest 64-bit version of Notepad++]. 

[https://downloads.tuflow.com/_archive/Miscellaneous/NPP_TUFLOW_Syntax_Highlighting.zip TUFLOW syntax highlighting for Notepad++]. 

For instructions on configuring Notepad++ for TUFLOW modeling, see [[NotepadPlusPlus_Tips |Notepad++ tips]].
|-
| '''Microsoft Excel''' || A spreadsheet software is required for working with tabular data and .csv files. This tutorial has been created using Excel. ||
|}

=Tutorial Data=
To build the tutorial model, download the dataset below. This includes a digital elevation model (DEM), aerial photography, background model data for the tutorial models and a working version of each model.
:*[https://downloads.tuflow.com/TUFLOW/Wiki_Tute_Models/TUFLOW_CATCH_Tutorial_Models.zip TUFLOW CATCH Tutorial Dataset - QGIS]

=Tutorial Modules=
The download dataset contains the input files and working version of the tutorial models for reference. Results and check files are not included to keep the size of the download file manageable; they will be created when running the model simulations. The folder should be placed in a location with write permissions. 

There are four tutorial models. All models can be completed independently, however it is encouraged to complete them in sequence:

:*[[TUFLOW_CATCH_Tutorial_M01 | TUFLOW CATCH Tutorial 01]] - Pollutant Export
:*[[TUFLOW_CATCH_Tutorial_M02 | TUFLOW CATCH Tutorial 02]] - Interventions
:*[[TUFLOW_CATCH_Tutorial_M03 | TUFLOW CATCH Tutorial 03]] - Hydrology
:*[[TUFLOW_CATCH_Tutorial_M04 | TUFLOW CATCH Tutorial 04]] - Integrated

== TUFLOW CATCH Documentation ==
TUFLOW CATCH documentation can be found in the TUFLOW CATCH Manual and the TUFLOW CATCH Changelog.

* [https://docs.tuflow.com/catch/manual/latest/ TUFLOW CATCH Manual]
* [https://docs.tuflow.com/catch/changelog/ TUFLOW CATCH Changelog]

=Contact=

For comments, requests and feedback contact [mailto:support@tuflow.com support@tuflow.com]. 
For further training opportunities see [https://tuflow.com/training/training-course-catalogue/ TUFLOW Training Catalogue] and/or contact [mailto:training@tuflow.com training@tuflow.com]. 
 

{{Tips Navigation
|uplink=[[Main_Page| Back to Wiki Main Page]]
}}

Tutorial M05 Results QGIS

2026-05-26T04:02:16Z

Emilie Nielsen: Reverted edit by Anne.Kolega (talk) to last revision by Emilie Nielsen

=Introduction=
QGIS is used to view the 1D time series results with the TUFLOW Viewer. For viewing of the 2D map results, see [[Tutorial_M01_Results_QGIS | Module 1]]. 
 

=Method=
Plot Time Series results through the pipe network:
<ol>
<li>Open the TUFLOW Viewer.
<li>Select File > Load Results. Navigate to the '''M05_5m_001.tcf''' in the '''Module_05\TUFLOW\runs''' folder and open it.
<li>When prompted to 'Open Result GIS Layer', click 'Yes'. This loads in all of the 1D and 2D results.
<li>Two additional files appear in the Layers panel:
*'''M05_5m_001_PLOT_L'''
*'''M05_5m_001_PLOT_P'''
<li>Select the '''M05_5m_001_PLOT_L''' file in the Layers panel and using the 'Select Features' tool highlight one of the 1d_nwk lines (to highlight multiple hold down shift).
<li>Select one of the Time Series datasets shown with the [[File:results_2.png | 15px]] icon and the 'Time Series' tab gets updated. 
 
{{Video|name=Animation_M05_Result_01f.mp4|width=1223}} 
 
</ol>
Plot longitudinal profiles from the Time Series datasets: 
<ol>
<li>The available long profile result types have a long profile icon [[File:Image XSLongProfile.png]] and display in the 'Cross Section / Long Profile' tab. 
 
{{Video|name=Animation_M05_Result_02g.mp4|width=1223}} 
</ol>
 

=Conclusion=
:*Both the 1D and 2D results were viewed confirming the the pipe network was getting flows through the pit 1D/2D links and the water was discharging from the downstream pipe to the 2D domain.
:*For further functionality, see [[TUFLOW_Viewer | TUFLOW Viewer]].
 
{{Tips Navigation
|uplink=[[Tutorial_M05#Results| Back to Module 5 Main Page]]
}}

Tutorial M03 Results QGIS

2026-05-25T23:54:48Z

Emilie Nielsen:

= Introduction =
QGIS is used to view the 1D time series results with the TUFLOW Viewer. For viewing of the 2D map results, see [[Tutorial_M01_Results_QGIS | Module 1]]. 
 

= Method =
Plot Time Series results through the culverts:
<ol>
<li>Open the TUFLOW viewer.
<li>Select File > Load Results. Navigate to the '''M03_5m_001.tcf''' in the '''Module_03\TUFLOW\runs''' folder and open it.
<li>When prompted to 'Open Result GIS Layer', click 'Yes'. This loads in all of the 1D and 2D results.
<li>Two additional files appear in the Layers panel:
*'''M03_5m_001_PLOT_L'''
*'''M03_5m_001_PLOT_P'''
<li>Select the '''M03_5m_001_PLOT_L''' file in the Layers panel and using the 'Select Features' tool highlight one of the 1d_nwk lines.
<li>Select one of the Time Series datasets shown with the [[File:results_2.png | 15px]] icon and the 'Time Series' tab gets updated. 
 
{{Video|name=Animation_M03_Results_01e.mp4|width=1258}} 

</ol>
Plot longitudinal profiles from the Time Series output: 
<ol>
<li>The available long profile result types have a long profile icon [[File:results_lp_v2.png | 15px]] and display in the 'Cross Section / Long Profile' tab. 
 
{{Video|name=Animation_M03_Results_02e.mp4|width=1258}} 
</ol>
 

= Conclusion =
:*The 1D results were assessed including time series and long profile results.
:*For further functionality, see [[TUFLOW_Viewer | TUFLOW Viewer]].
 
{{Tips Navigation
|uplink=[[Tutorial_M03#Results| Back to Module 3 Main Page]]
}}

File:TUFLOW Viewer legacy icon.png

2026-05-25T00:08:49Z

Emilie Nielsen:

TUFLOW 2D Hydraulic Structures

2026-04-21T23:43:05Z

Emilie Nielsen: /* 2D Layered Flow Constriction (2d_lfcsh) */

= 2D Structure Modelling Theory =
The theory behind the modelling of energy losses and affluxes of hydraulic structures is presented in the following webinars by Bill Syme and Greg Collecutt (TUFLOW Developers).

*[https://www.tuflow.com/library/webinars/#structures Webinar Link: Modelling Energy Losses at Structures] 
*[https://www.tuflow.com/library/webinars/#nov2022_hydraulic_modelling_bridge Webinar Link: 1D, 2D & 3D Hydraulic Modelling of Bridges]
 

= 2D Bridge Modelling in TUFLOW - Overview =
The TUFLOW 2D solution explicitly predicts the majority of “macro” losses due to the expansion and contraction of water through a constriction, or around a bend, provided the resolution of the grid is sufficiently fine ([https://www.tuflow.com/Download/Publications/Flow%20Through%20an%20Abrupt%20Constriction%20-%202D%20Hydrodynamic%20Performance%20and%20Influence%20of%20Spatial%20Resolution,%20Barton,%202001.pdf Barton, 2001]; [https://www.tuflow.com/Download/Publications/Modelling%20of%20Bends%20and%20Hydraulic%20Structures%20in%20a%202D%20Scheme,%20Syme,%202001.pdf Syme, 2001]; [https://www.tuflow.com/Download/Technical_Memos/Modelling%20Bridge%20Piers%20in%202D%20using%20TUFLOW.pdf Ryan, 2013]). Where the 2D model is not of fine enough resolution to simulate the “micro” losses (e.g. from bridge piers, vena contracta, losses in the vertical (3rd) dimension), additional form loss coefficients and/or modifications to the cells widths and flow height need to be added.
==Contraction/Expansion Losses (“Macro” Losses)==
Loss of energy is caused by the flow contraction during the expansion of water after the vena-contracta inside a bridge section and the flow expansion downstream a bridge. As discussed above, this type of "macro" losses can be explicitly resolved by the TUFLOW 2D solver, provided that a proper turbulence model and mesh size are used. Below is an example of the 2D modelling of flow contraction/expansion at a pair of bridge abutments.
 
[[File:FC_Velocity_Example.PNG|600px]] 

==Pier Losses==
Piers are usually smaller than the 2D cell size in real-world flood models. Although flexible mesh solver or quadtree refinement can be applied to reduce the local cell size around the pier, it also comes with an expensive computational cost that could significantly increase the simulation time. More practically, the backwater effect of piers can be modelled as sub-grid form losses.

Pier form loss coefficients can be derived from information in publications such as [https://www.fhwa.dot.gov/engineering/hydraulics/library_arc.cfm?pub_number=1&id=5 ''Hydraulics of Bridge Waterways'' (Bradly, 1978)] or [https://austroads.com.au/publications/bridges/agbt08 ''Guide to Bridge Technology Part 8: Hydraulic Design of Waterway Structures'' (AUSTROADS, 2018)]. Energy loss estimated from bridge piers or other obstructions, vertical or horizontal, that do not cause upstream controlled flow regimes like pressure flow, are dependent on the ratio of the obstruction's area perpendicular to the flow direction to the gross flow area of the bridge opening, the shape of the piers or obstruction, and the angularity of the piers/obstruction to the flow direction. For example, using Hydraulics of Bridge Waterways (Bradly, 1978) the approach is:
<ol>
<li>Calculate the ratio of the water area occupied by piers to the gross water area of the constriction (both based on the normal water surface) and the angularity of the piers. These inputs are used to calculate "J" in the FHA documentation.</li>
<li>Use the Figure 4.10 ''Incremental Backwater Coefficient for Piers'' data to calculate Kp. 
[[File:incremental_backwater_coefficient_2018_pier_losses.png]]
 
'''NOTE''': the pier form loss coefficients in Hydraulics of Bridge Waterways are derived based on the cross-sectional averaged velocity through the bridge opening in the absence of piers. It's not necessary to specify a blockage value if a pier form loss coefficient estimated from this method is used.
</li>
</ol>

==Bridge Deck and Rail (Super Structure)==
When a bridge deck become partially or completely submerged, the deck could generate extra afflux resulting in increased water levels and flood extents upstream of the structure. The flow around the deck is highly 3-dimentional and complexed due to the different deck designs/profiles and/or the occurrence of pressure flow. In 2D SWE solver, depth-varying form loss values are often needed to reproduce the afflux caused by such structure. Due to the complexity of the flow, guidelines on how to set the form loss coefficient for the bridge deck are rare. We have carried out a joint research with QLD TMR (Queensland Department of Transport and Main Roads) regarding how to choose a proper form loss value for the bridge deck [https://tuflow.com/media/7554/2022-bridge-deck-afflux-modelling-benchmarking-of-cfd-and-swe-codes-to-real-world-data-collecutt-et-al-hwrs.pdf (Collecutt et al, 2022)] . In the research, CFD modelling was conducted to investigate the characteristics of energy loss of a simple bridge with a flat bottomed deck and guardrails.
 
[[File:CFD_study.png|600px]]

Below are the key findings from the study:
*The results displayed a characteristic shape for head loss coefficient as a function of downstream water level over the deck thickness (TW/T).
*The head loss (afflux) peaks when the water level is approximately 1.6*T above the bridge soffit, and decays slowly as the bridge becomes progressively drowned out.
[[File:FormLoss_vs_TWT.png|600px]]
 

=== Bridge Design (hB/T) vs Form Loss Coefficient Table===
The peak loss coefficient value is a function of the ratio of the depth underneath the deck (hB) and the thickness of the deck (T). This table can be used to estimate the deck form loss coefficient based on the bridge design (hB/T).
<ol>
{| style="text-align: center;" class="wikitable" width="35%"
! style="background-color:#005581; font-weight:bold; color:white;" width=55%| Deck Height to Thickness Ratio
! style="background-color:#005581; font-weight:bold; color:white;" width=45%| Peak Form Loss Coefficient
|-
| Scenario A (hB/T) = 2 || 0.42
|-
| Scenario B (hB/T) = 4 || 0.28
|-
| Scenario C (hB/T) = 6 || 0.20
|}
</ol>

*The solid portion of the guard rails (blockage * rail depth) can be added to T in addition to the deck thickness to calculate hB/T.
*For bridge with more complicated designs (e.g. girders), higher form loss might be required due to the higher surface roughness of the bridge.
*If the hB/T ratio is less than 2 or greater than 6, use a peak form loss coefficient of 0.42 (minimum) or 0.20 (maximum), respectively.

'''NOTE''': This form loss value should not be confused with the value of 1.56 used in the pressure flow approached adopted in [[1D_Bridges | TUFLOW 1D "B" and "BB" bridge]]. TUFLOW 1D bridge pressure flow approach is based on the section 4.13.2 "All Girders in Contact with Flow (Case II)" of ''Guide to Bridge Technology Part 8: Hydraulic Design of Waterway Structures'' (AUSTROADS, 2018). The original hydraulic experiment conducted by [https://hdl.handle.net/10217/39009 Liu et al (1957)] in a laboratory flume with a pair of bridge abutments and a deck. The flow conditions were similar to orifice flow due to the high blockage ratio caused by the abutments and the deck. When modelling bridges in 2D, the contraction/expansion losses caused by the abutments would be handled explicitly by the 2D solver, so a value 1.56 can lead to duplication of the contraction/expansion losses caused by the bridge abutments. 
 

=TUFLOW 2D Bridge Setup=
There are two methods available to model depth varying form loss of a bridge structure:
* [[TUFLOW_2D_Hydraulic_Structures#2D_Layered_Flow_Constriction_.282d_lfcsh.29 |2D Layered Flow Constriction (2d_lfcsh)]]
:The traditional method used to model depth-varying form loss through bridge components such as piers, decks, and rails.

*[[TUFLOW_2D_Hydraulic_Structures#2D_BG_Shape_.282d_bg.29 |2D BG Shape (2d_bg)]] (introduced in the 2023 release)
:A simplified approach developed to simplify the model input based on the findings from the joint TMR Study [https://tuflow.com/media/7554/2022-bridge-deck-afflux-modelling-benchmarking-of-cfd-and-swe-codes-to-real-world-data-collecutt-et-al-hwrs.pdf (Collecutt et al, 2022)].

Both methods provide options for representing flow surcharging, the pressure flow of bridge decks and eventually submerged bridge flow at higher water levels. During the surcharging of bridge decks, higher energy losses can be specified to simulate the pressure flow.

Examples for how to configure both approaches are provided in the 2D structures section of the [[TUFLOW_Example_Models#2D_Structures |TUFLOW Wiki Example Models]] and [[Tutorial_M04 |Tutorial Module 4]] - 2D Bridges.

==2D Layered Flow Constriction (2d_lfcsh)==
Four flow constriction layers are represented in a 2d_lfcsh layer. The lower three layers represents the pier, the bridge deck and the rails. Each layer has its own attributes to specify the blockage and the form loss coefficient. The top (fourth) layer assumes the flow is unimpeded, representative of flow over the top of a bridge. Within the same shape, the invert of the bed, and thickness of each layer can vary in 3D.

The following table provides an overview for how to determine the blockage and form loss coefficient for each layer. Note that this is just an overview and additional guidelines may need to be considered. 
{| style="text-align: left; margin-left: 0; " class="wikitable" width="80%"
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Layer
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Description
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Blockage (%)
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Form Loss Coefficient (FLC)
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Notes
|-

| 1 || Pier layer || ~5% (can be omitted if included in FLC) || Estimate using [[TUFLOW_2D_Hydraulic_Structures#Pier_Losses | Pier Losses]] || Represents flow obstruction from piers beneath the bridge deck
|-
| 2 || Bridge deck || 100% || Use calibration data, if available, to determine FLC. If no calibration is available, estimate using [[TUFLOW_2D_Hydraulic_Structures#Bridge_Design_.28hB.2FT.29_vs_Form_Loss_Coefficient_Table | hB/T vs FLC]] table || Full blockage, no flow through the deck
If using the [[TUFLOW_2D_Hydraulic_Structures#Bridge_Design_.28hB.2FT.29_vs_Form_Loss_Coefficient_Table | hB/T vs FLC]] table, it is recommended to enable the Method C Form Loss Approach
|-
| 3 || Bridge rails || 10% – 100% || Use calibration data, if available, to determine FLC. 
If no calibration data is available, combined FLC for Layers 2 and 3 should be estimated using the [[TUFLOW_2D_Hydraulic_Structures#Bridge_Design_.28hB.2FT.29_vs_Form_Loss_Coefficient_Table | hB/T vs FLC]] table, where T = L2_Depth + (pBlockage × L3_Depth)
*(pBlockage × L3_Depth) represents the solid portion of the rails
*L2 FLC and L3 FLC should sum to the combined FLC
|Blockage and FLC depends on rail type Sensitivity testing with 100% blockage is recommended due to potential for debris during flood
If using the [[TUFLOW_2D_Hydraulic_Structures#Bridge_Design_.28hB.2FT.29_vs_Form_Loss_Coefficient_Table | hB/T vs FLC]] table, it is recommended to enable the Method C Form Loss Approach
|-
| 4 || Above rails || 0% || 0 || Represents unimpeded overtopping flow
|}
<ol>
[[File:2d_lfcsh_attributes_02.jpg|700px]]
</ol>
 

===Blockage===

The 2d_lfcsh functions by adjusting the flow width and the form loss of 2D cell faces. The combined blockage across the 4 layers is calculated at each simulation timesteps:
<ol>
 
[[File: Blockage_total_equation_01.png|600px]]
 
where 
'''''yi''''' is the actual depth of water in layer '''''i''''' 
'''''ytotal''''' is the total water depth 
</ol>

===Form Loss Approach===

The combined form loss coefficient is determined using one of three methods. The form loss coefficient method can be specified either individually using the 2d_lfcsh “Shape_Options” attribute or globally using the .tcf command: 
<tt>Layered FLC Default Approach == [ METHOD A | {METHOD B} | METHOD C | METHOD D]</tt> 

:METHOD A: The losses are accumulated as the water level rises through the layers. 
<ol>
[[File:Eq_flc_cumulate.png |450px]]
</ol>
:*Layer 1: Constant form loss (L1_FLC)
:*Layers 2 & 3: Form loss increases based on the depth of water in layer 2 & 3; peak form loss at top of Layer 3
:*Above Layer 3: Applies the full accumulated form loss continuously, even when overtopping begins (no reduction)
:Note: Simpler method but tends to overestimate losses when the structure is submerged or overtopped 

:METHOD B (default): the losses are applied pro-rata according to the depth of water in each layer. 
<ol>
[[File:Eq_flc_portion.png |430px]]
</ol>
:*Layer 1: Constant form loss (L1_FLC)
:*Layers 2 & 3: Form loss increases based on the depth of water in layer 2 & 3; peak form loss at top of Layer 3
:*Above Layer 3: Total form loss gradually reduces as water overtops the structure
:Note: Maintains backward compatibility but may underrepresent losses during pressurised or overtopped flows 

:METHOD C (recommended): hybrid approach combining Method A and Method B. 
<ol>
[[File:Eq_flc_methodC.png |520px]]
</ol>
:*Layer 1: Constant form loss (L1_FLC)
:*Layers 2 & 3: Gradual increase in form loss with water level, following Method A
:*Above Layer 3: Total form loss gradually reduces as water overtops the structure, following Method B
:Note: Recommended method; aligns closest to CFD modelling results and TUFLOW HPC behaviour.

:METHOD D: Allows the modeller to control the depth at which the losses start to reduce when the flow transitions between pressure flow and drowned flow.
:This approach is the same used by the 2d_bg layer (introduced in the 2023-03 release). It is recommended to use the 2d_bg layer as it has the benefit of a simplified attribute table, for easier user input.

===Form Loss Calibration Example - Iowa River Flood Study===

In this study, a combined form loss coefficient of 0.35 was used to match observed head loss during slight overtopping of a bridge. The FLC values for each layer were adjusted to achieve the correct combined form loss. The table and plot show how each layer contributes to the total form loss and highlight the differences in calculated form loss between the three methods.

{| style="text-align: left; margin-left: 0;" class="wikitable" width="60%"
!colspan="1" rowspan="2" style="background-color:#005581; font-weight:bold; color:white;" width=6%| Layer
!colspan="1" rowspan="2" style="background-color:#005581; font-weight:bold; color:white;" width=10%| Depth (m)
!colspan="1" rowspan="2" style="background-color:#005581; font-weight:bold; color:white;" width=12%| Blockage (%)
!colspan="2" style="background-color:#005581; font-weight:bold; color:white;" width=20%| Method A
!colspan="2" style="background-color:#005581; font-weight:bold; color:white;" width=20%| Method B
!colspan="2" style="background-color:#005581; font-weight:bold; color:white;" width=20%| Method C
|-
! style="background-color:#005581; font-weight:bold; color:white;"| Layer FLC
! style="background-color:#005581; font-weight:bold; color:white;"| Combined FLC
! style="background-color:#005581; font-weight:bold; color:white;"| Layer FLC
! style="background-color:#005581; font-weight:bold; color:white;"| Combined FLC
! style="background-color:#005581; font-weight:bold; color:white;"| Layer FLC
! style="background-color:#005581; font-weight:bold; color:white;"| Combined FLC
|-
| 1 || 5.0 || 5 || 0.07 || 0.07 || 0.07 || 0.07 || 0.07 || 0.07
|-
| 2 || 1.5 || 100 || 0.15 || 0.22 || 1.05 || 0.30 || 0.15 || 0.22
|-
| 3 || 1.0 || 50 || 0.13 || 0.35 || 0.70 || 0.35 || 0.13 || 0.35
|}

</ol>
 
<ol>
[[File:FLC_vs_height_updated.png | 600px ]]
</ol>

==2D BG Shape (2d_bg)==
2D BG Shape is similar to the Layered Flow Constriction, but has several updates to simplify the input based on the findings from the joint study with TMR [https://tuflow.com/media/7554/2022-bridge-deck-afflux-modelling-benchmarking-of-cfd-and-swe-codes-to-real-world-data-collecutt-et-al-hwrs.pdf (Collecutt et al, 2022)].

The following table provides an overview of how to determine the blockage and form loss coefficient for each layer. Note that this is just an overview and additional guidelines may need to be considered. 
{| style="text-align: left; margin-left: 0; " class="wikitable" width="80%"
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Layer
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Description
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Blockage (%)
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Form Loss Coefficient (FLC)
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Notes
|-

| 1 || Pier layer || ~5% (can be omitted if included in FLC) || Estimate using [[TUFLOW_2D_Hydraulic_Structures#Pier_Losses | Pier Losses]] || Represents flow obstruction from piers beneath the bridge deck
|-
| 2 || Bridge deck || 100% || rowspan="2" | The Super Structure (Super_S) is the bridge deck and rails layers combined. 
Use calibration data, if available, to determine FLC. 
If no calibration data is available, the Super_S FLC should be estimated using the [[TUFLOW_2D_Hydraulic_Structures#Bridge_Design_.28hB.2FT.29_vs_Form_Loss_Coefficient_Table | hB/T vs FLC]] table, where T = Deck_Depth + (Rail_pBlockage*Rail_Depth)
*(Rail_pBlockage*Rail_Depth) represents the solid portion of the rails
|| Full blockage, no flow through the deck
|-
| 3 || Bridge rails || 10% – 100% || Sensitivity testing with 100% blockage is recommended due to potential for debris during flood events
|-
| 4 || Above rails || 0% || 0 || Represents unimpeded overtopping flow
|}

<ol>
[[File:Bridge block.jpg | 800px]]
</ol>

===Inflection Point===

Based on findings from the joint study [https://tuflow.com/media/7554/2022-bridge-deck-afflux-modelling-benchmarking-of-cfd-and-swe-codes-to-real-world-data-collecutt-et-al-hwrs.pdf (Collecutt et al, 2022)], the head loss peaks when the water level is approximately 1.6*T above the bridge soffit, and decays slowly as the bridge becomes progressively drowned out. The 'SuperS_IPf' attribute (inflection point factor, default = 1.6) can be used to define the height of the inflection point. The solid portion of the rail layer is also added to the deck thickness to calculate the depth to the inflection point (DIP), i.e.:
<ol>
[[File:eq_flc_bg_infection_point.png | 520px ]]
</ol>

===Form Loss Approach===
The form loss approach is similar to the FLC approach METHOD C, with L2/L3 replaced by a single super structure layer:
<ol>
[[File:eq_flc_bg.png | 480px ]]
</ol>

===Form Loss Calibration Example - Iowa River Flood Study===
This example uses the same bridge setup described in the[[TUFLOW_2D_Hydraulic_Structures#Form_Loss_Calibration_Example_-_Iowa_River_Flood_Study | 2D Layered Flow Constriction]] section, with the following parameters applied:
*SuperS_FLC = 0.28
*SuperS_Ipf = 1.6,
The Depth to Inflection Point (DIP) is calculated as 3.2m above the bridge soffit.

The table and figure below show how the form loss value varies with water depth.
<ol>
{| style="text-align: center;" class="wikitable" width="32%"
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;" width=8%| Layer
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;" width=8%| Depth (m)
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;" width=8%| Blockage (%)
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;" width=8%| Form Loss
|-
| Pier || 5.0 || 5 || 0.07
|-
| Deck || 1.5 || 100 || rowspan="2" | 0.28
|-
| Rail || 1.0 || 50
|}

[[File:FLC_vs_height_bg.png | 600px ]]
</ol>

== 2D Bridges Line vs Polygon Layer ==
The form loss coefficient (FLC) is applied differently when using a line compared to a polygon for both 2d_lfcsh and 2d_bg inputs. The FLC is applied at cell sides (u and v faces) as this is where velocities are calculated. 
For larger bridges that spread across multiple cells, it is recommended to use a polygon layer, which selects all u and v faces falling within the polygon.
 
 
'''2D Layered Flow Constriction (2d_lfcsh)'''
{| style="text-align: left; margin-left: 0;" class="wikitable" width="80%"
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 7.5%;"| Geometry
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 7.5%;"| Line Type
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 11%;"| Width Attribute
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 22%;"| FLC Input
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 22%;"| FLC Applied
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 30%;"| Notes
|-
!rowspan="3" | Line
| Thin
| zero
| Total form loss of the bridge
| Applies the FLC to a single row of cell sides
| This approach is cell size independent. It is the easiest setup and the preferred / recommended approach when using 2d_lfcsh.
|-
| Thick
| between zero and 1.5 times the cell size
| Total form loss of the bridge
| FLC/2 applied to all sides of the selected cells
| A cell is selected if the polyline intersects the cell crosshair. Caution should be taken when using a "thick" line, as changes in cell size can cause it to become a "wide" line. If this occurs, the FLC attribute may need to be recalculated to avoid overestimating or underestimating losses.
|-
| Wide
| larger than 1.5 times the cell size
| Total form loss of the bridge ''(may need to be recalculated, see notes)''
| FLC divided by number of cell sides in the direction of flow 
''(number of cell sides in the direction of flow is calculated as line width divided by cell size)''
| Polygon shapes are recommended if more than 3 rows of faces must be selected.. 
Caution should be taken when using a "wide" line. The cell size and alignment of the 2d_lfcsh line may result in selecting too many or too few cell faces in the direction of the flow. The FLC input may need to be recalculated to ensure FLC Applied multiplied by the number of cell sides in the direction of flow equates to the intended total form loss.
|-
!rowspan="1" | Polygon
| -
| -
| Total loss per unit length (meters or feet) in the direction of flow
| FLC * cell size applied to all sides of selected cells
|
|}

'''2D Bridge (2d_bg)'''
{| style="text-align: left; margin-left: 0;" class="wikitable" width="80%"
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 7.5%;"| Geometry
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 7.5%;"| Line Type
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 11%;"| Width Attribute
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 22%;"| FLC Input
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 22%;"| FLC Applied
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 30%;"| Notes
|-
!rowspan="3" | Line
| Thin
| zero
| Total form loss of the bridge
| Applies the FLC to a single row of cell sides.
| This approach is cell size independent.
|-
| Thick
| larger than zero
| Total form loss of the bridge
| FLC/2 applied to all sides of the selected cells
| This approach is cell size independent. A cell is selected if the polyline intersects the cell crosshair.
|-
| Wide
| Not supported
| –
| –
| BG polygon shapes are recommended if more than 3 rows of faces must be selected.
|-
!rowspan="1" |Polygon
| -
| ''(used to automatically distribute the total FLC to the selected faces)''
| Total form loss of the bridge
| FLC / Deck_Width * cell size applied to all sides of selected cells
| For bridges modelled using a 2d_bg polygon the relative ratio of the bridge width to the 2D cell size should be 4 or greater. For more information on this see [https://downloads.tuflow.com/Other/2d_bg_R_Bridge_Configuration_Advice_202503.pdf 2d_bg_R_Bridge_Configuration_Advice.pdf].
|}
 
The following diagrams demonstrate how the input FLC is applied for the four geometry options for 2d_lfcsh and 2d_bg layers: 
[[File:2dlfcsh 2dbg combined v2.png|1200px]]

It is good modelling practice to check the [[Check_Files_2d_lfcsh_uvpt | lfcsh_uvpt_check]] and [[Check Files 2d bg uvpt check | bg_uvpt_check]] files to confirm the number of faces selected and the FLC values assigned. It is also strongly recommended to undertake a sensitivity analysis on the applied form losses in the model to check if it makes any difference to the results and/or double check against other methods (hand calculations, other software, CFD modelling), especially if the bridge is near an area of interest. If calibration data is available, this should be used to guide the form loss value specification. 
 

= Common Questions Answered (FAQ)=
== What blockage values should I use for bridge guard rails? ==
The blockage of bridge guard rails can be anything from 100% blocked (solid concrete rails) to 10% blocked (very open rails). In addition, the accumulation of debris during a flood can be substantial as shown in the image below. Sensitivity testing with 100% blockage is recommended.
 
[[File:Bridge rail debris.jpg | 500px]]

== How to conduct sensitivity test for 2D bridges? ==
General recommendations to cross-check the results are:
* Compare computed affluxes against desktop methods (e.g. Hydraulics of Bridge Waterways, 1978) and/or other software including CFD, especially for unusual bridge designs.
* Use any recorded flood marks or general observations from past events to check and calibrate FLC values.
* Conduct sensitivity testing by assessing the impact and influence of FLC values on your modelling objectives. The afflux resulting from the FLC values will be proportional to the velocity head, i.e. ∆h=FLC*(v^2/2g). As such, if velocities are low (e.g. 1 m/s), the results may not be overly sensitive to uncertainties in the FLC values. If completing a check using this equation for a long skew bridge it is best to calculate the total structure velocity from a PO line digitised in the same location as the bridge.

Finally, after completing sensitivity testing and understanding the range of uncertainty due to unknowns like the degree of blockage and influence of FLC values (e.g. +/-20%), you are in a position to discuss with your client how best to proceed. For example, if the modelling is to set planning levels for a development upstream then it may be appropriate to choose values on the higher side (higher FLC values and/or blockage assumptions), noting that the uncertainty may be amply covered by a regulatory freeboard. Conversely, if the development is on the downstream side the conservative approach would be to use the results at the lower end of your FLC/blockage values. 
[[File:Bridge Flood Debris Loading.jpg | 500px]] 

== Should I use both FLC and blockage for layer one in 2D bridge layered flow constriction? ==
When applying FLC and blockage values to model obstructions such as piers, the following considerations need to be taken into account:
* The FLC value applies an energy loss along 1D channels or across 2D cell faces equivalent to FLC*V2/2g where V is the 1D channel velocity or the 2D cell face velocity.
* FLC values are often sourced from publications such as Hydraulics of Bridge Waterways or AustRoads (e.g. Kp chart for piers).
* If possible, establish whether the source of the FLC value is based on the approach velocity (the velocity in the absence of piers) or structure velocity (the velocity with area blocked out by the piers) noting that it often isn’t clear or stated.
** If it is the structure velocity, this is usually the velocity at the vena-contracta (point of greatest contraction within the entrance to the structure and therefore highest velocity) - see image below. Bluff or sharp-edged obstructions will have a much more pronounced vena-contracta, and therefore higher velocity compared with a round-edged obstruction.
** FLC values based on the approach velocity will be higher than those based on the structure velocity to achieve the same energy loss.
* Applying a blockage equivalent to the obstruction width will increase, usually very slightly, the velocity of the 1D channel or 2D cell face. This won’t be the vena-contracta velocity, but a velocity between the approach velocity and the vena-contracta velocity. A greater blockage will need to be applied to emulate the vena-contracta velocity.
* If the FLC source value is based on:
** The approach velocity then there is no need to apply a blockage value.
** The structure velocity then the blockage value should be applied noting that it may be appropriate to apply a larger blockage to take into account the vena-contracta.
* If it is not clear or unknown whether the FLC source value is based on the approach or structure velocity, the recommendation would be to apply the blockage in the interests of being slightly conservative on the upstream flood level calculation.
* For most minor obstructions such as bridge piers, the blockage is usually relatively small and whether included or not has a negligible or minor affect on flood levels compared with other factors such as the approach embankments and the bridge deck.
* Blockage from debris wrapped around piers can have a greater influence on the results than the effect of applying or not applying a blockage. Debris wrapped around piers can be accounted for in the FLC value calculated for the pier layer.
* As always, sensitivity testing with and without blockage and +/- the FLC value is highly recommended to understand their importance in regard to the broader modelling objectives and the effects of uncertainties in the input data, boundaries, other parameters such as Manning’s n values, and the accuracy of the numerical solution scheme (see [https://www.tuflow.com/library/webinars/#maximise_accuracy Maximising the Accuracy of Hydraulic Models webinar]).
[[File: Vena_contracta.png]] 
''Image showing the formation of the vena-contracta.'' 
 

==I don't see results that I expect when using 2d_lfcsh layer==
The 2d_lfcsh layer is a versatile feature that was designed to model bridges in 2D, but can also be used for other applications like fences, buildings raised on pillars and so on.
Some of the unexpected results could be:
* Water level going through the bridge deck in 2D map output.
* Water transiting through 100% blocked Layer 1, e.g. fences with solid base.
* SHMax.csv reporting values above the bridge deck when 2D map output reports water level lower than the top of the bridge deck.

TUFLOW is a 2D solution (not 3D), in the 2d_lfcsh layer the percent blockage and form loss coefficient applied to the cell faces is depth averaged across the entire cell face (across Layer 1, 2 and 3): 
*For bridges, where Layer 2 has a 100% blockage applied, the minimum flow width of 0.001m is used and is averaged with the Layer 1 blockage (based on the depth of the water). This may result in a water level being reported within or above the bridge deck, which would represent the pressure head.
*Layered flow constriction works by adjusting the flow area of the cell faces by any blockages to generate the correct depth averaged velocity at each face at which the form losses are applied as a fraction of the V2/2g kinetic energy. Calculating the correct velocity is critical for determining the losses as the losses are proportional to the velocity squared. 
*For a layered flow constriction cell face the flow area cannot be zero above the invert of Layer 1 to avoid a divide by zero in the computations, therefore a minimum average flow width after applying blockages of 0.001 m is applied. if Layer 1 is 100% blocked, a very small amount of water will flow through Layer 1. If this is unacceptable, instead of applying 100% blockage of Layer 1, the preferred approach is to start the layered flow constriction at the top of Layer 1 or raise the ground elevation to the top of Layer 1 using one of the Z Shape modification functions (e.g. a breakline). 
<ol>
[[File:100% Blockage Diagram.png | 500px]]
</ol>

== Can I model bridge piers explicitly in 2D using very small cells? ==
It isn't recommended to explicitly model bridge piers by blocking out the pier faces in TUFLOW, or in any hydraulic modelling software based on solving Shallow Water Equations(SWE). Due to the 3-dimentiality of the flow and turbulence around a pier, computational fluid dynamics (CFD) approach is often required to simulate the flow around piers explicitly. The wake turbulence behind a simple-shape pier can be resolved to some extent using extremely fine mesh in TUFLOW (see calibration example to a flume experiment in the [https://www.tuflow.com/library/webinars/#structures webinar on Energy Losses at Structures]), however the predictions for head losses show notable sensitivities to the mesh size, the mesh design, and the choice of turbulence model. The extremely fine mesh resolution also results in significantly higher computational costs.

Therefore, the safest and strongly recommended approach with regard to establishing head losses and consequently flood levels, is to model the effects of such obstructions with form loss coefficients (applied to selected mesh cells) that have been derived from physical testing. This approach has been shown to provide the most consistent results across various mesh resolutions. It also has the added benefit that, by avoiding small cells in the mesh, it will provide much more efficient run times for flow solvers.

[[File:Flow round a cylinder.png]]

''The point of flow separation around an object has a major bearing on the drag coefficient and is not reliably reproduced by 2D or 3D software.''


== How to best convert flow constriction data (2d_fc or 2d_fcsh) into newer formats (2d_lfcsh or 2d_bg)? ==
The form loss parameters can be transferred from the flow constriction (2d_fc or 2d_fcsh) to the first layer of the layered flow constriction (2d_lfcsh) or pier layer of the 2d_bg. Definition of the remaining form loss and blockage layer inputs should follow the guidance outlined in [[TUFLOW_2D_Hydraulic_Structures#2D_Layered_Flow_Constriction_.282d_lfcsh.29 | 2D Layered Flow Constriction]] and [[TUFLOW_2D_Hydraulic_Structures#2D_BG_Shape_.282d_bg.29 | 2D BG Shape]] paragraphs. 
When using floating pontoon (type FD in the 2d_fc or 2d_fcsh) different setup might need to be used for different events. For large events when floating pontoon becomes fixed at the top of the supporting piles, standard 2d_lfcsh setup can be used. Smaller events when the pontoon is floating at different heights might require more sensitivity testing of the structure parameters to find out a setup the matches the reality as close as possible. 

== Should I model bridges in 1D or 2D Domain? ==
The recommended approach typically depends on the study objectives and if the channel upstream and downstream of the bridge is modelled in 1D or 2D. To preserve the momentum as accurately as possible the bridge should be modelled in the same dimension as the channel, e.g. 1d_nwk bridge if the channels is in 1D and 2d_bg or 2d_lfcsh if the channel is modelled in 2D. 
In 2D, the expansion/contraction losses are modelled based on the topography and don't need to be estimated as attributes as for 1D modelling. Also, for higher flows where the bridge is overtopped, 2D is preferable approach.

== What is the difference between downstream and upstream controlled flow? ==
Downstream control means a change in downstream water level will cause a change in upstream water level. Upstream control means the upstream water level is insensitive to the downstream water level and usually indicates the occurrence of supercritical flow.

== What FLC values should be used for 2d_bg bridge if hB/T is below 2 or above 6? ==
TMR has extended the CFD simulation to hB/T ratios of 1 to 10. Refer to the [https://docs.tuflow.com/classic-hpc/manual/latest/ TUFLOW Manual] for details.

If hB/T is outside this ratio:
* hB/T ratios of less than 1 represent a very unusual bridge sitting low to the ground, and the peak FLC may increase above the end value (FLC of 0.6) in a way that doesn't follow the research trend or extrapolation. For these cases we would recommend using CFD modelling to obtain a more informed value. Alternatively, computing an FLC based on pressure flow or using 1D culvert might be considered.
* For hB/T ratios of greater than 10, the FLC is likely to continue to decrease, but probably not significantly. Clamping to the end value (FLC of 0.16) might be considered the more conservative approach (if the primary concern is flood levels upstream of the bridge). 
 
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File:2d lfcsh attributes 02.jpg

2026-04-21T23:42:06Z

Emilie Nielsen:

1D Pumps

2026-04-21T03:58:33Z

Emilie Nielsen: /* 2D-2D Configuration */

=Introduction=
This post provides a modelling example for a 1D pump using a pump curve. For this example we will set up a pump in two common situations (2D-2D & 1D-2D).

=Pump Attributes=
A pump needs to first be digitised in a 1d_nwke layer. The direction of the polyline must go from inlet to outlet as a pump is unidirectional. The attributes required for a pump in your 1d_nwk layer can be found in the [https://docs.tuflow.com/classic-hpc/manual/latest/ TUFLOW Manual]. 
In the 1d_nwk layer, the following attributes are required: 
#ID = ID of the pump channel. 
#Type = "P" or "PO". 
#US_Invert = Intake elevation of the pump. 
#DS_Invert = Outlet elevation of the receptor. 
#Inlet_Type = Used to specify the pump curve in the Depth Discharge database. 
#Width_or_D = Diameter of the pump’s outlet pipe/hose. 
#Number_of = Number of (identical) pumps.
 
[[File:1d_nwk_pump_pipe.PNG|border|300px]] 

=2D-2D Configuration=
As pumps are zero length channels, they do not create automatic nodes at the upstream and downstream end. If you ran the model with just a pump polyline and SX connection, you will get [[TUFLOW_Message_1353| ERROR 1353]]. To remove this error, the most efficient schematisation is to digitise a 1d_nwk 'NODE' at the upstream and downstream end of the pump (no need for a separate 2d_bc SX layer). Unlike NODEs connected to pipes and channels, NODEs connected to zero length pumps require the following attributes: 
#Type = "NODE". 
#Len_or_NA = The 'NODE' requires a nominal storage amount. This can be estimated from the pipe length and diameter attached to the pump. 
#US_Invert = The upper elevation of the automatically created NA table. Make sure these values are set higher than the expected water levels at the intake and outlet of the pump. 
#DS_Invert = The bottom elevation of the pump nodes. As the pump does not create automatic nodes, the bottom elevation of the pump nodes must be specified. Note that this does not change the intake or outlet elevations of the pump, but only sets the bottom elevation of the nodes for storing water. 
#Conn_1D_2D = Set to "SX" to connect the 1D pump with the 2D domain. Without the SX connection, water will build up within the node and cause instabilities. 

See the example below. 

[[File:1d_nwk_pump_SX_node.png|600px]] 

A simple 2D-2D pump configuration will look like the below schematisation. 

[[File:Pump_schematic.PNG|600px]] 

=1D-2D Configuration=
Connecting a pump from a 1d network to the 2d domain or vice versa is similar to the configuration above, the only difference is that the connection with a 1d structure does not require a 1d nwk ‘Node’. A storage chamber in the 1d network can also be modelled using a 1d_na node with an elevation vs area .csv assigned to the node. 
[[File:1D-2D_pump_schematisation.PNG|border|600px]] 

=Estry Control File Setup=
Within the *.ecf the following commands and files are required to run a pump with no logical controls: 
<tt>Read GIS Network</tt> <tt>==</tt><tt>..\model\mi\1d_nwke_xxxxx.MIF</tt> 
<tt>Depth Discharge Database</tt> <tt>==</tt><tt>..\bc_dbase\xxxxx.csv</tt> 
If you do not specify a Depth-Discharge database then you will be faced with [[TUFLOW Message 1118 | ERROR 1118]]. 

=TUFLOW Operating Control File (.TOC)=
For guidance on setting up the operating controls for pumps, refer to the [https://docs.tuflow.com/classic-hpc/manual/latest/ TUFLOW Manual]. 

.ecf command required: 

<tt>Read Operating Controls File</tt> <tt>==</tt><tt> xxxxx.toc</tt> 

=Depth Discharge Database=
The depth discharge database is set up in the same way as a pit inlet database (refer to the [https://docs.tuflow.com/classic-hpc/manual/latest/ TUFLOW Manual]). Each pump ‘Inlet_type’ must reference a name within the depth discharge database, otherwise [[TUFLOW_Message_1118 | ERROR 1118]] - Could not find pit inlet type ",a," in the pit inlet database. The ‘Area (m2)’ column is the area of the pump offtake and ‘Width (m)’ column is the width of the pump offtake. Without information in the Area(m2) or Width(m) columns in the depth discharge database [[TUFLOW Message 1092|ERROR 1092]] and [[TUFLOW Message 1093|ERROR 1093]] will appear. 

==Pump Curve==
The performance of pumps is a function of suction head at the inlet and the level of the discharge location. The resultant total head between the water level at the inlet and outlet is what determines the flow rate through the pump. If the suction level is low the pump will need to provide more energy in the form of pressure to maintain the water elevation at the outlet, the opposite is also true if the water depth at the pump inlet is high. 

[[File:pump_fundamentals_total_head.jpg|thumb|none|500px|www.pumpfundamentals.com]]

That being the case it is important to consider what total head is required to achieve the modelling objectives and what flow rates you may require. Once you have an idea on any limits in total head you can start to research an appropriate pump and then extract the performance curve that is often incorporated as part of the technical specifications. An example is shown below. 

[[File:Manufacturer pump curve.JPG|border|600px]]

==Creating a TUFLOW pump curve==
The setup of the Depth Discharge database for a pump curve is similar to reading in inflow hydrographs, hyetographs etc, that is; a source .csv, and the two corresponding headings within the 3rd and 4th column. 

[[File:depth-discharge_pump.PNG |border|500px]] 

Once you have your manufacturer curve for your given pump it is now necessary to create the curve .csv for TUFLOW to read in. The manufacturer specifications will need to be translated into a total head vs pump rate chart. Although reading in the depth discharge database is the same process as other boundary conditions within TUFLOW, the curve itself is fundamentally different as you no longer need to start the csv file with 0,0. If the curve did start at 0,0 this would not make sense because at a total head difference of 0m the pump should effectively be operating at peak performance so the flow rate would be greater than 0 m3. The image below shows a csv file for the pump performance curve given in the previous section. 
 
[[File:Pump_curve_csv_example.png|border|600px]] 

==Using a Pump Curve in a TUFLOW Operating Control (TOC) File==

With the pump curve defined in the depth-discharge database it can either be specified within the pump 1d_nwk fields in the inlet_type field, for non-operational pumps, or it can be defined with the TOC file, for operational pumps. When defining with a TOC file, the pump curve is defined at the top of the structure control definition block and then the subsequent rules can turn the pump on/off. See the below TOC structure control definition for an example. In this case, the pump curve is used when the pump switches on once upstream water levels reach 2.75m AD. The pump curve is then used until the upstream water levels are reduced to 2.25m AD at which point the pump is switched off.

<tt>Define Pump Control</tt><tt> ==</tt> Pump_1
<tt>Pump Capacity</tt><tt> ==</tt> pump_1
HU <tt>==</tt> H1D Pump1.1
<tt>If </tt>HU <= 2.25
<tt>Pump Operation</tt><tt> ==</tt> Off
<tt>Else if</tt> HU > 2.25 <tt>AND</tt> HU < 2.75
<tt>Pump operation</tt><tt> ==</tt> <tt> No Change </tt>
<tt>Else if</tt> HU <tt>>=</tt> 2.75
<tt>Pump Operation</tt><tt> ==</tt> On
<tt>End if</tt>
<tt>End define</tt>

=1D Result File=
Although strictly not a check file, the operation of the pump can be confirmed by opening the *_1d_O.csv which is found within the csv folder where the results are written. The *_1d_O.csv monitors the operation of structures, this file can be quite useful in checking how the structure is performing with the given .toc file and GIS inputs. 
{| align="center" class="wikitable" width="75%"
! style="background-color:#005581; font-weight:bold; color:white;"| Filename prefix / suffix
! style="background-color:#005581; font-weight:bold; color:white;" width=75%| Brief Description
|-
| [[Pump_Results_1d_O | _1d_O.csv]]|| This csv displays the status of the pump, whether that is closed or fully open, results for any logic parameter specified in the TOC file and the flow through the pump if it is in operation.
|}
 
Any further questions please email TUFLOW support: [mailto:support@tuflow.com?Subject=TUFLOW%201D%20pumps%20help support@tuflow.com]
 
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Advection Dispersion Modelling

2026-04-20T00:57:19Z

Emilie Nielsen: /* Introduction */

=Introduction=
TUFLOW’s Advection Dispersion (AD) functionality is an extension of the TUFLOW Classic/HPC engines available within the TUFLOW CATCH module. It adds to the hydrodynamic capabilities of TUFLOW Classic/HPC by simulating depth-averaged, two and one-dimensional constituent fate and transport. An example of such a constituent might include salinity. Both dissolved and particulate constituents can be simulated. TUFLOW AD takes depth and velocity fields computed by the TUFLOW Classic and HPC solvers and uses this information, together with initial and boundary conditions, to simulate the advection and dispersion of user-defined constituents.

TUFLOW AD is specifically oriented towards such analyses in systems including coastal waters, estuaries, rivers, floodplains and urban areas. The AD functionality is discussed in detail in the [https://docs.tuflow.com/classic-hpc/manual/latest/ TUFLOW Manual - Chapter 9].

TUFLOW FV also has Advection Dispersion functionality. In many cases, it's preferable to use TUFLOW FV for AD modelling due to its functionality with flexible mesh. See the [https://docs.tuflow.com/fv/manual/latest/ TUFLOW FV Manual] for details.

=Model Development=
==Setting Up a New Model==
The steps below describe the process for setting up a TUFLOW AD model. It is assumed that the user is familiar with TUFLOW Classic/HPC and that the folder structure for TUFLOW has been setup with all required files. The user should run the TUFLOW Classic/HPC model without the AD functionality first to make sure that it is appropriately configured and stable.

<ol>
<li>Create a TUFLOW AD control file with the extension .adcf
<li>Use a text editor to create an empty .adcf file and save it to the “runs” folder.

<li>Set up the AD global database (.csv file).
<li>Set up the TUFLOW AD global database in the “bc_dbase” folder which defines the constituent of interest and a number of characteristics, for example the decay rate and dispersion coefficient. The resulting file should look similar to the below: 
[[File:EG17 AD Consit 001.png]] 

<li>In the .adcf file use the "AD Global Database" command to set the location of the global database as follows. <tt>AD Global Database</tt><tt> == </tt><tt>..\bc dbase\my_ad_global_dbase.csv</tt>

<li>Set up the boundary condition tables (.csv file(s)) to define the time-varying constituent concentrations at any input boundaries.
<ul><li>Set up the constituent boundary condition table(s) in the “bc_dbase” folder. For example in the below, the time-varying concentration of constituents Conc_AD1 and Conc_AD2 are set: 
[[File:EG17 conc 001.png]] </ul>
<li>Set up up the boundary condition database (.csv file)
<ul><li>Set up the boundary condition database in the “bc_dbase” folder that references the tables set up in the previous step. 
[[File:EG17 AD 001.png]] 
<li>In the .adcf file use the "AD BC Database" command to set the location of the bc database as follows. <tt>AD BC Database</tt><tt> == </tt><tt>..\bc dbase\my_ad_bc_dbase.csv</tt></ul>
<li>Setup up TUFLOW to activate the AD functionality (.tcf file)
<ul><li>In the .tcf file use the command "AD Control File" to set the location of the adcf and activate execution of the AD functionality as follows. <tt>AD Control File</tt><tt> == </tt><tt>ad_run.adcf</tt></ul>
<li>Run the model
<li>Run TUFLOW as normal. The AD functionality will be utilised and appropriate constituent result output files written.

</ol>

==Example Models==
Example TUFLOW AD models, including settling and decay, are available via the [[TUFLOW_Example_Models#Advection_Dispersion | TUFLOW Example Model Dataset]].

= Common Questions Answered (FAQ) =

== How can the Advection Dispersion functionality be used to determine the time of concentration in a 1D-2D TUFLOW model? ==
The Advection Dispersion functionality can track particles and determine the time of concentration by simulating how a particle of water travels from an upstream to a downstream location. However, the AD functionality is only available for 2D domains and cannot directly operate within a 1D channel.

To utilise the AD functionality in this case, the 1D channel would need to be converted into a 2D domain using a Quadtree grid. This conversion involves refining the 2D cells within the channel to smaller sizes, ensuring the model accurately represents the flow behaviour. Once this modification is complete, the AD functionality can provide detailed insights into particle travel times and help demonstrate the effects of reprofiling or attenuation measures on downstream areas.

== Can TUFLOW generate 2D Plot (Time-Series) Output for Advection Dispersion results? ==
Currently, TUFLOW does not support 2D Plot (Time-Series) Output for Advection Dispersion results at specific point locations.

However, results can be extracted using output zones. Defining smaller output zones allows high-frequency data to be generated for areas of interest while managing file sizes efficiently. Multiple output zones can also be used to monitor widely separated locations.

== How can initial tracer concentrations and SGS parameters be managed in the Advection Dispersion functionality? ==
Initial tracer concentrations can be applied to dry cells, and these concentrations are mobilised as the cells become wet during a simulation. The initial water level in dry cells is set as the bed elevation plus the Cell Wet/Dry Depth. This depth determines the initial tracer volume available for advection once the cell becomes inundated.

When SGS (Sub-Grid Sampling) is used, the initial water volume is derived from a pre-calculated “level vs cell volume” curve. Tracer concentrations are distributed across this calculated volume. This ensures accurate representation of tracer movement, even in partially wet cells.

== How can the Advection Dispersion functionality be used to determine water residency time? ==
The Advection Dispersion functionality in TUFLOW can be used to calculate water residency time by modelling it as a scalar variable. This approach provides a method for tracking the duration water has spent within a specific area, such as a wetland, and is visualised in the model output as a time-based scalar field. This approach has some limitations:
* Output Capabilities: While TUFLOW supports various output formats (e.g., XMDF, DAT, NC), extracting detailed time-series data for specific constituents at individual locations may require additional post-processing. The current AD functionality does not explicitly support direct Point Output (PO) functionality for constituent data.
* Post-Processing Requirements: To obtain detailed residency time information at specific points, output zones may be required along with refined post-processing techniques. Defining output zones allows high-frequency scalar data to be captured in areas of interest, which can then be analysed to estimate residency times.
* Engine-Specific Features: Unlike the TUFLOW FV engine, which includes a particle tracking module for explicit tracking of water age, the fixed grid engine’s AD module relies on scalar-based methods to approximate residency time. For calculating water residency time with the AD functionality, properly configuring scalar outputs and planning post-processing steps are essential for accurate results.

== How can the Advection Dispersion functionality simplify firewater containment modelling? ==
The Advection Dispersion functionality in TUFLOW can simplify firewater containment modelling by using passive tracers to track firewater flow and concentration. Instead of running separate simulations for rainfall and firewater scenarios, the AD functionality enables a single simulation where tracers represent the firewater. This approach reduces modelling complexity while maintaining accuracy.

For example, a model with direct rainfall over the entire domain applies a passive tracer via 2d source area (2d_sa) polygons. The output can be set up to identify areas with tracer concentrations above a certain threshold, distinguishing firewater extents from other inundated areas. Areas outside of this represent zones with zero tracer concentration. Tracers can also include decay and settling parameters for added flexibility. This method not only simplifies the process but also ensures compliance with the UK CIRIA (Construction Industry Research and Information Association) guidance by integrating rainfall and firewater scenarios into a single simulation.

== What guidance is available for Non-Newtonian mixing exponents and dispersion coefficients in the Advection Dispersion functionality? ==
The Non-Newtonian Mixing Exponents (m, o, and p) were introduced in the 2023-03-AC release to improve how TUFLOW models non-Newtonian fluids. These exponents control how yield stress and density change as fluid concentration varies.

Previously, using a single exponent for all properties was ineffective for fluids with high solids content. For example, yield stress can increase rapidly with small changes in solids, while density changes more gradually.

It is recommended that these exponents range between 1 and 5. However, the optimal values depend on the specific fluid being modelled, and should be selected based on the fluid’s properties. TUFLOW does not provide specific default values.

For dispersion coefficients:

* In pure water, the longitudinal dispersion coefficient (KL) is usually between 6 and 13, and the transverse dispersion coefficient (KT) is between 0.15 and 1.6.

* Extremely high values, like 7500, only occur in special conditions such as estuarine environments with a halocline and are not typical for most cases.

Currently, there is no guidance for dispersion coefficients when mixing pure water with non-Newtonian fluids. Suitable values should be determined based on laboratory tests or studies specific to the fluid being modelled.

== What are the limitations of the Advection Dispersion functionality when modelling Non-Newtonian flow through 1D elements? ==
When using the Advection Dispersion functionality for non-Newtonian flow in models that include 1D elements, the following simplifications and limitations apply:

Flow Calculation:
* The flow through 1D elements (e.g., culverts) is calculated based on the assumption of pure water.
* Non-Newtonian properties, such as viscosity or yield stress, are not considered in the 1D engine. This simplification can lead to an overestimation of flow rates when dealing with non-Newtonian fluids.
Tracer Transport:
* By default, the concentration of the non-Newtonian fluid is passed instantly from the upstream to the downstream node in 1D channels.
* The transport equation is not calculated for the 1D elements. This can cause an underestimation of travel time for non-Newtonian fluids, particularly in long 1D elements.

These limitations mean that while the AD module can be used in models with 1D elements, it does not fully capture the complexities of non-Newtonian fluid behaviour in those elements. If higher accuracy is required, 2D elements where non-Newtonian properties are more comprehensively represented may be considered.

== Can the Advection Dispersion functionality be used in a model to simulate salinity? ==
Yes, the Advection Dispersion functionality can be used with models to simulate salinity transport, as long as the system is relatively well mixed vertically.

TUFLOW HPC is a 2D shallow water equation solver, so it does not account for vertical salinity gradients. This means it is best suited for rivers, shallow lakes, and estuaries where haloclines are weak or absent. Different boundary inflows can be assigned varying time series of salinity concentrations, and the module will simulate how these mix over space and time.

If the system has strong density stratification or distinctly three dimensional flow behaviour, a fully 3D solver such as TUFLOW FV is recommended.

== Can the Advection Dispersion functionality simulate pollutant runoff and transport from catchments? ==
Yes, the Advection Dispersion functionality can also be used to simulate pollutant runoff from catchments. This includes modelling the generation, transport, and fate of pollutants such as suspended sediment, nitrogen, and phosphorus.

Pollutants can be generated based on modelled bed shear stress, then transported through the domain using the flow field. The model can also apply decay and settling rates as part of the simulation.

The TUFLOW CATCH module, with which the Advection-Dispersion functionality is included, provides the capability to simulate pollutant runoff and transport from catchments. See the [https://www.tuflow.com/products/tuflow-catch-module/ TUFLOW Website] for further information.

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Tutorial M02

2026-04-10T05:20:53Z

Emilie Nielsen: /* Impact Assessment */

= Introduction =
In the first part of this module, breaklines are added to ensure that the key hydraulic controls are correctly represented in the 5m cell size model. The second part involves simple and more complex development topographic modifications. 

The GIS layers are: 
:*TGC layers:
<ol><ol><li>2d_zsh: A layer used to modify Zpt elevations using points, lines and polygons.</li>
<li>2d_mat: A layer used to define the land use (material) types within the developmental area.</li></ol></ol>
'''Module 2 builds from the model created in [[Tutorial_M01 | Module 1]]. The completed Module 1 model is provided in the Module_02\TUFLOW folder.''' 
 

=Part 1 - Breaklines=
The first part of this module introduces breaklines for road crests.

There are a few ways to model breaklines based on the models cell size. The Shape_Width attribute controls the width of the breakline: 
:*Thin Breakline: Shape_Width equal to 0 - only elevations on the cell sides and cell corners are modified, no change in storage.
:*Thick Breakline: Shape_Width less than or equal to 1.5 times the cell size - entire cells are modified, storage changes with changing elevation of the cell centres.
:*Wide Breakline: Shape_Width greater the 1.5 times the cell size - any elevation points within a distance of half the Shape_Width attribute are modified, storage changes.

== GIS Inputs ==
Create, import and view input data: 
:*[[Tutorial_M02_001_GIS_Inputs_QGIS | QGIS - SHP]]
:*[[Tutorial_M02_001_GIS_Inputs_QGIS_GPKG | QGIS - GPKG]]

== Simulation Control Files ==
=== TUFLOW Geometry Control File (TGC) ===
<ol>
<li>Save a copy of '''M01_001.tgc''' as '''M02_001.tgc''' in the '''Module_02\TUFLOW\model''' folder. 
<li>Open the '''M02_001.tgc''' in a text editor and add the following line after the '<tt>Read GRID Zpts</tt> <tt> == </tt> <tt>grid\DEM.tif</tt>' command. Note, the points and lines are in separate layers, but are part of the same breakline, therefore they are input on the same line with a vertical bar '|' to tell TUFLOW the layers are linked. The TUFLOW modelling convention is to list the lines first and then points. 
'''QGIS - SHP''' 
<tt>Read GIS Z Shape </tt> <tt>== </tt> <tt>gis\2d_zsh_M02_rd_crest_001_L.shp | gis\2d_zsh_M02_rd_crest_001_P.shp </tt> <tt> ! Defines the road crest</tt> 
'''QGIS - GPKG''' 
<tt>Read GIS Z Shape </tt> <tt>== </tt> <tt>2d_zsh_M02_rd_crest_001_L | 2d_zsh_M02_rd_crest_001_P </tt> <tt> ! Defines the road crest</tt> 
<li>Save the TGC.
</ol>

=== TUFLOW Control File (TCF) ===
<ol>
<li>Save a copy of '''M01_5m_001.tcf''' as '''M02_5m_001.tcf''' in the '''Module_02\TUFLOW\runs''' folder.
<li>Open the file '''M02_5m_001.tcf''' in a text editor and make the following reference updates: 
'''QGIS - SHP''' 
<tt>Geometry Control File </tt> <tt>== </tt> <tt>..\model\M02_001.tgc </tt> <tt> ! Reference the TUFLOW Geometry Control File</tt> 
'''QGIS - GPKG''' 
<tt>Spatial Database </tt> <tt>== </tt> <tt>..\model\gis\M02_001.gpkg </tt> <tt> ! Specify the location of the GeoPackage Spatial Database</tt> 
<tt>Geometry Control File </tt> <tt>== </tt> <tt>..\model\M02_001.tgc </tt> <tt> ! Reference the TUFLOW Geometry Control File</tt> 
<li>Save the TCF.
</ol>

== Running the Simulation ==
Run the model using a batch file. Batch files include a wide array of TUFLOW options and functions, such as running multiple simulations in series or parallel, testing model initialisation and even copying models for transfer between modellers or organisations. For more information, see [[Run_TUFLOW_From_a_Batch-file | Run TUFLOW From a Batch file]]. 
<ol>
<li>Save a copy of '''_run_M01_HPC.bat''' as'''_run_M02_HPC.bat''' in the '''Module_02\TUFLOW\runs''' folder.
<li>Open the '''_run_M02_HPC.bat''' in a text editor and update the text: 
<tt>'''set'''</tt> <tt>exe</tt><tt>=</tt><tt>"..\..\..\exe\2026.0.0\TUFLOW_iSP_w64.exe"</tt> 
<tt>'''set'''</tt> <tt>run</tt><tt>=</tt><tt>start "TUFLOW" /wait</tt> <tt> %exe%</tt> <tt> -b</tt> 
<tt>%run% </tt> <tt>M02_5m_001.tcf </tt> 
:*The '<tt>'''set'''</tt> <tt>exe</tt>' command specifies the link to the TUFLOW executable. This file path may need to be changed depending on the folder set up. 
:*The '<tt>'''set'''</tt> <tt>run</tt>' command contains a series of commands:
::*<tt>start</tt>: Opens each simulation in a separate console window.
::*<tt>"TUFLOW"</tt>: Sets 'TUFLOW' as the title of the console window.
::*<tt>/wait</tt>: If multiple simulations are to be run, it is often desirable to run these in series, i.e. the second simulation starts after the first finishes. The /wait switch makes the batch file wait until the process is finished before moving onto the next command.
::*<tt>%exe%</tt>: executes tasks specified in the variable called ‘exe’, in this case the TUFLOW executable.
::*<tt>-b</tt>: The use of the –b (batch mode) switch suppresses the need to press the return key at the end of a simulation. This ensures that one simulation proceeds on to the next without any need for user input. This is required for running multiple simulations in series (one after the other).
:*The '<tt>%run%</tt>' executes tasks specified in the variable called ‘run’.
<li>Save the batch file and double click it in file explorer to run the simulation.
</ol>

== Troubleshooting ==
See tips on common mistakes and troubleshooting steps if the model doesn't run:
:*[[Tutorial_Troubleshooting_QGIS | QGIS]]

== Check Files ==
While the model is running, check that the added features are specified correctly:
:*[[Tutorial_M02_001_Check_Files_QGIS | QGIS - SHP]]
:*[[Tutorial_M02_001_Check_Files_QGIS_GPKG | QGIS - GPKG]]

== Results ==
For viewing of the 2D map results, see [[Tutorial_M01#Results | Module 1]]. 

Suggestions for an investigation: 
:*Does the flooding still overtop the roads? 
<ol>Tip: check the maximum 2D results. </ol>
:*What is the difference in peak water level at the upstream of the roads compared to the Module 1 run? 
<ol>Tip: Use the ‘Plot Time Series from Map Output’ tool in the TUFLOW Viewer QGIS Plugin. </ol> 

=Part 2 - Other Topographic Updates=
The second part of this module introduces a range of options to make both simple and complex topography modifications. It also introduces an additional materials file to reflect the changes of land use based on the complex topography modifications. 
There are a few ways to create polygon topographic modifications based on the Shape_Option attribute:
:*Merge - merges the elevations at polygon perimeter vertices with the topography Zpt values.
:*No merge - assigns a single elevation to all Zpts falling within the polygon.
:*Add - raises or lowers the polygon by a fixed value.
:*TIN functionality - uses combination of points, lines and polygons to create complex topographic modifications.

== GIS Inputs ==
Create, import and view input data:
:*[[Tutorial_M02_002_GIS_Inputs_QGIS | QGIS - SHP]]
:*[[Tutorial_M02_002_GIS_Inputs_QGIS_GPKG | QGIS - GPKG]]

== Simulation Control Files ==
=== TUFLOW Geometry Control File (TGC) ===
<ol>
<li>Save a copy of the '''M02_001.tgc''' as '''M02_002.tgc''' in the '''Module_02\TUFLOW\model''' folder.
<li>Open the '''M02_002.tgc''' in a text editor and add the following lines after the road crest input. 
'''QGIS - SHP''' 
<tt>Read GIS Z Shape </tt> <tt>== </tt> <tt>gis\2d_zsh_M02_fill_002_R.shp </tt> <tt> ! Defines areas of imported fill</tt> 
<tt>Read GIS Z Shape </tt> <tt>== </tt> <tt>gis\2d_zsh_M02_merge_002_R.shp </tt> <tt> ! Defines areas of merging topography</tt> 
<tt>Read GIS Z Shape </tt> <tt>== </tt> <tt>gis\2d_zsh_M02_cut_002_R.shp </tt> <tt> ! Defines excavation through embankment</tt> 
<tt>Read GIS Z Shape </tt> <tt>== </tt> <tt>gis\2d_zsh_M02_landscape_002_R.shp | gis\2d_zsh_M02_landscape_002_L.shp | gis\2d_zsh_M02_landscape_002_P.shp </tt> <tt> ! Defines areas of complex landscaping</tt> 
'''QGIS - GPKG''' 
<tt>Read GIS Z Shape </tt> <tt>== </tt> <tt>2d_zsh_M02_fill_002_R </tt> <tt> ! Defines areas of imported fill</tt> 
<tt>Read GIS Z Shape </tt> <tt>== </tt> <tt>2d_zsh_M02_merge_002_R </tt> <tt> ! Defines areas of merging topography</tt> 
<tt>Read GIS Z Shape </tt> <tt>== </tt> <tt>2d_zsh_M02_cut_002_R </tt> <tt> ! Defines excavation through embankment</tt> 
<tt>Read GIS Z Shape </tt> <tt>== </tt> <tt>2d_zsh_M02_landscape_002_R | 2d_zsh_M02_landscape_002_L | 2d_zsh_M02_landscape_002_P </tt> <tt>
! Defines areas of complex landscaping</tt> 
As the points, lines and regions are in separate files, but are part of the same topographic modification, they are input on the same line with a vertical bar '|' to tell TUFLOW the layers are linked. The TUFLOW modelling convention is to list the polygons first, then lines and points last.
<li>Add in the following line after the '<tt>Read GIS Mat</tt>' command. 
'''QGIS - SHP''' 
<tt>Read GIS Mat </tt> <tt>== </tt> <tt>gis\2d_mat_M02_landscape_002_R.shp </tt> <tt> ! Sets the material values according to attributes in the GIS layer</tt> 
'''QGIS - GPKG''' 
<tt>Read GIS Mat </tt> <tt>== </tt> <tt>2d_mat_M02_landscape_002_R </tt> <tt> ! Sets the material values according to attributes in the GIS layer</tt> 
Assigns the updated materials values due to the development. As the order of commands in the TGC is critical, ensure this command is written after the original <tt>Read GIS Mat</tt> command.
<li>Save the TGC.
</ol>

=== TUFLOW Control File (TCF) ===
<ol>
<li>Save a copy of '''M02_5m_001.tcf''' as '''M02_5m_002.tcf''' in the '''Module_02\TUFLOW\runs''' folder.
<li>Open the file '''M02_5m_002.tcf''' in a text editor and make the following reference updates: 
'''QGIS - SHP''' 
<tt>Geometry Control File </tt> <tt>== </tt> <tt>..\model\M02_002.tgc </tt> <tt> ! Reference the TUFLOW Geometry Control File</tt> 
'''QGIS - GPKG''' 
<tt>Spatial Database </tt> <tt>== </tt> <tt>..\model\gis\M02_002.gpkg </tt> <tt> ! Specify the location of the GeoPackage Spatial Database</tt> 
<tt>Geometry Control File </tt> <tt>== </tt> <tt>..\model\M02_002.tgc </tt> <tt> ! Reference the TUFLOW Geometry Control File</tt> 
<li>Save the TCF.
</ol>

== Running the Simulation ==
Update the batch file created in the first part of Module 2 to reference the '''M02_5m_002.tcf''' file. Save the batch file and double click it in file explorer to run the simulation. 

== Troubleshooting ==
See tips on common mistakes and troubleshooting steps if the model doesn't run:
:*[[Tutorial_Troubleshooting_QGIS | QGIS]]

== Check Files ==
While the model is running, review the added features are specified correctly:
:*[[Tutorial_M02_002_Check_Files_QGIS | QGIS - SHP]]
:*[[Tutorial_M02_002_Check_Files_QGIS_GPKG | QGIS - GPKG]]

== Results ==
For viewing of the 2D map results, see [[Tutorial_M01#Results | Module 1]]. 
=== Impact Assessment ===
The [[ASC_to_ASC| asc_to_asc]] utility with difference flag is used to plot the flood level changes resulting from the topography updates. The utility is provided in the '''exe\asc_to_asc''' folder. It can also be downloaded from the [https://www.tuflow.com/downloads/ TUFLOW website] and saved into a folder with other utilities. 
<ol>
<li>Create a new batch file '''_M02_asc_to_asc_Level_Difference.bat''' in the '''Module_02\TUFLOW\results\grids''' folder and open it in a text editor.
<li>Input the following (Note: Utility location may differ): 
<tt>'''set''' </tt> <tt>asc_to_asc</tt><tt>=</tt><tt>"..\..\..\exe\asc_to_asc.2024-06-AF\asc_to_asc_w64.exe"</tt> 
<li>Use the -dif flag to call the difference function. The utility then expects two grid files, it subtracts the first grid from the second. Add the following syntax below the 'set asc_to_asc' command. 
<tt>%asc_to_asc% </tt> <tt>-b -dif M02_5m_002_h_Max.tif M02_5m_001_h_Max.tif </tt> 
<li>Optional is to use the -out flag to specify the name of the output grids. 
<tt>%asc_to_asc% </tt> <tt>-b -dif -out M02_Level_Difference M02_5m_002_h_Max.tif M02_5m_001_h_Max.tif </tt> 
<li>Save the batch file and double click it in file explorer to run the utility.
<li>The resulting difference grids appear in the same folder location, open these in a GIS software to see the effects of the topography changes on the flood levels.
*M02_Level_Difference.tif = difference in maximum flood level.
*M02_Level_Difference_wd.tif = change in flood extent, identifying cells that were once wet, now dry (-99) and once dry, now wet (99). 
 

[[File:M02_ImpactMap_c.png]] </ol>
 

= Conclusion =
:*Breaklines and different polygon topographic modifications were added to the model.
:*Check files were assessed to view the changes on the underlying topographic model.
:*Impact assessment was conducted using the asc_to_asc utility.
:*For further training opportunities see [https://tuflow.com/training/training-course-catalogue/ TUFLOW Training Catalogue] and/or contact [mailto:training@tuflow.com training@tuflow.com]. 
 
{{Tips Navigation
|uplink=[[Tutorial_Introduction| Back to Tutorial Introduction Main Page]]
}}

File:M02 ImpactMap c.png

2026-04-10T05:20:17Z

Emilie Nielsen:

HPC Introduction

2026-04-10T02:05:29Z

Emilie Nielsen: /* Introduction */

=Introduction=
Since the 2017-09-AA version, TUFLOW offers HPC (Heavily Parallelised Compute) as an alternate 2D Shallow Water Equation (SWE) solver to TUFLOW Classic.

TUFLOW HPC is now industry standard. While TUFLOW Classic is still supported, it is recommended to use TUFLOW HPC.

TUFLOW Classic is limited to running a simulation on a single CPU core, whereas HPC provides parallelisation of the TUFLOW model allowing modellers to run a single TUFLOW model across multiple CPU cores or GPU graphics cards (which utilise thousands of smaller CUDA* cores). Simulations using GPU hardware has shown to provide significantly quicker model run times for TUFLOW users. 

In general, most of the functionality and features of TUFLOW Classic are available in HPC. Additionally, HPC offers several advanced features not supported in Classic, including:
* Quadtree and sub-grid sampling
* High resolution map output grids
* Groundwater infiltration and sub-surface flows
* Wu turbulence formulation
* TMR bridge inputs (2d_bg) and simulation methods

===Solution Scheme, Cell Discretisation and Parallelisation===
TUFLOW HPC is an explicit solver for the full 2D Shallow Water Equations (SWE), including a sub-grid scale eddy viscosity model. The scheme is both volume and momentum conserving, is 2nd order in space and 4th order in time, with adaptive or fixed timestepping. It is unconditionally stable. TUFLOW HPC's computational approach differs from TUFLOW Classic, which is a 2nd order (space) implicit finite difference solver. Both TUFLOW HPC and Classic solve the 2D SWE on the same uniform Cartesian grid configuration. Computationally each 2D cell includes 9 sub-grid points. 

[[File: HPC Cell Design.PNG |300px]] 

The ZC point:
* Defines the volume of active water (cell volume is based on a flat square cell that wets and dries at a height of ZC plus the Cell Wet/Dry Depth);
* Controls when a cell becomes wet and dry (note that cell sides can also wet and dry); and
* Determines the bed slope when testing for the upstream controlled flow regime.
The ZU and ZV points:
* Control how water is conveyed from one cell to another;
* Represent where the momentum equation terms are centred and where upstream controlled flow regimes are applied;
* Deactivate if the cell has dried (based on the ZC point) and cannot flow; and
* Wet and dry independently of the cell wetting or drying (see Cell Wet/Dry Depth). This allows for the modelling of “thin” obstructions such as fences and thin embankments relative to the cell size (e.g. a concrete levee).
ZH points:
* Play no role hydraulically. This point location is used for output processing;
* The only elevations written to the .2dm mesh file (by default, binary output is interpolated/extrapolated to the cell corners).

Within the above sub-grid framework, using TUFLOW HPC time derivatives of cell averaged water depth, u-velocity and v-velocity are computed on a cell-by-cell basis and the model evolved using an explicit ODE solver. Calculation of the cell based derivatives are highly independent of each other making it possible to run this solution scheme across multiple processors or GPU cards. Parallelisation is done by breaking up the model into vertical ribbons. Each ribbon of the model is run on a different processor (or GPU card) with boundary information shared between processors at each timestep. 

[[File: Mesh_Ribbon_Splitting.png |360px]] 

===Mass Conservation and Timestep===

The explicit finite volume solution scheme utilised in HPC is mass conserving by construction (0% mass error). This differs to TUFLOW Classic, which can continue to simulate a model with some volume error due to it being an implicit finite difference scheme. The stability of the explicit finite volume scheme used in TUFLOW HPC is linked to the timestep, flow velocities, water depth, and eddy viscosity. The maximum timestep that can be used while maintaining model stability changes as the model evolves. While it is possible to choose a fixed timestep ahead of time (similarly to TUFLOW Classic), shorter run times and guaranteed model stability from start to finish may be achieved through the use of adaptive timestepping where the solver continually modifies the timestep based on various stability criteria. This is explained in more detail in our [[HPC_Adaptive_Timestepping | Adaptive Timestepping]] page. 

===Compatible Graphic Cards (GPU) ===
TUFLOW HPC’s GPU hardware module is only compatible with NVIDIA architecture CUDA enabled GPU cards. AMD GPU cards are NOT compatible. A list of CUDA enabled GPUs can be found on the following website: http://developer.nvidia.com/cuda-gpus .
To check if your computer has an NVIDA GPU and if it is CUDA enabled:
* Right click on the Windows desktop;
* If you see “NVIDIA Control Panel” or “NVIDIA Display” in the pop up dialogue, the computer has an NVIDIA GPU;
* Click on “NVIDIA Control Panel” or “NVIDIA Display” in the pop up dialogue;
* The GPU model should be displayed in the graphics card information;
* Check to see if the graphics card is listed on the following website: http://developer.nvidia.com/cuda-gpus
On the NVIDA website each CUDA enabled graphics card has a “Compute Capability” listed. For cards with a compute capability of 1.2 or less, only the single precision version of the GPU Module can be utilised. However, benchmarking has indicated that the double precision version is NOT required and that the TUFLOW_iSP exe should be used for all TUFLOW HPC GPU simulations. Extensive GPU hardware benchmarking has been undertaken to assist users who are upgrading hardware for TUFLOW modelling. Over 50 different hardware options have been tested for their speed performance. The results are provided on the [[Hardware_Benchmarking | Hardware Benchmarking]] page.

===Benefits of HPC===
So what does this mean for modellers? 
By providing the ability to run models on Graphics Cards, we can achieve significantly shorter model run times, increasing our modelling capabilities to be able to run continuous hydraulic models, with higher cell resolution, across larger extents and more scenarios. Common TUFLOW HPC applications include:
* Monte Carlo design assessments
* Rainfall ensemble design assessments
* High resolution 1D underground / 2D above ground integrated urban drainage
* High resolution floodplain lumped hydrology / hydraulic modelling (either fully 2D or including nested 1D open channels and pipes)
* Whole of catchment direct rainfall
* Flood forecast modelling
* Long-term water resource management modelling

The unconditional stability and higher order accuracy of TUFLOW HPC also lends itself well to highly transient situations, such as dam break assessments, where other solvers would either become unstable, lose accuracy or experience impractical simulation slow-down due to the need to solve at an extremely small timestep. 
 
{{Tips Navigation
|uplink=[[ HPC_Modelling_Guidance | Back to HPC Modelling Guidance]]
}}

TUFLOW 2D Hydraulic Structures

2026-04-10T02:03:26Z

Emilie Nielsen: /* 2D BG Shape (2d_bg) */

= 2D Structure Modelling Theory =
The theory behind the modelling of energy losses and affluxes of hydraulic structures is presented in the following webinars by Bill Syme and Greg Collecutt (TUFLOW Developers).

*[https://www.tuflow.com/library/webinars/#structures Webinar Link: Modelling Energy Losses at Structures] 
*[https://www.tuflow.com/library/webinars/#nov2022_hydraulic_modelling_bridge Webinar Link: 1D, 2D & 3D Hydraulic Modelling of Bridges]
 

= 2D Bridge Modelling in TUFLOW - Overview =
The TUFLOW 2D solution explicitly predicts the majority of “macro” losses due to the expansion and contraction of water through a constriction, or around a bend, provided the resolution of the grid is sufficiently fine ([https://www.tuflow.com/Download/Publications/Flow%20Through%20an%20Abrupt%20Constriction%20-%202D%20Hydrodynamic%20Performance%20and%20Influence%20of%20Spatial%20Resolution,%20Barton,%202001.pdf Barton, 2001]; [https://www.tuflow.com/Download/Publications/Modelling%20of%20Bends%20and%20Hydraulic%20Structures%20in%20a%202D%20Scheme,%20Syme,%202001.pdf Syme, 2001]; [https://www.tuflow.com/Download/Technical_Memos/Modelling%20Bridge%20Piers%20in%202D%20using%20TUFLOW.pdf Ryan, 2013]). Where the 2D model is not of fine enough resolution to simulate the “micro” losses (e.g. from bridge piers, vena contracta, losses in the vertical (3rd) dimension), additional form loss coefficients and/or modifications to the cells widths and flow height need to be added.
==Contraction/Expansion Losses (“Macro” Losses)==
Loss of energy is caused by the flow contraction during the expansion of water after the vena-contracta inside a bridge section and the flow expansion downstream a bridge. As discussed above, this type of "macro" losses can be explicitly resolved by the TUFLOW 2D solver, provided that a proper turbulence model and mesh size are used. Below is an example of the 2D modelling of flow contraction/expansion at a pair of bridge abutments.
 
[[File:FC_Velocity_Example.PNG|600px]] 

==Pier Losses==
Piers are usually smaller than the 2D cell size in real-world flood models. Although flexible mesh solver or quadtree refinement can be applied to reduce the local cell size around the pier, it also comes with an expensive computational cost that could significantly increase the simulation time. More practically, the backwater effect of piers can be modelled as sub-grid form losses.

Pier form loss coefficients can be derived from information in publications such as [https://www.fhwa.dot.gov/engineering/hydraulics/library_arc.cfm?pub_number=1&id=5 ''Hydraulics of Bridge Waterways'' (Bradly, 1978)] or [https://austroads.com.au/publications/bridges/agbt08 ''Guide to Bridge Technology Part 8: Hydraulic Design of Waterway Structures'' (AUSTROADS, 2018)]. Energy loss estimated from bridge piers or other obstructions, vertical or horizontal, that do not cause upstream controlled flow regimes like pressure flow, are dependent on the ratio of the obstruction's area perpendicular to the flow direction to the gross flow area of the bridge opening, the shape of the piers or obstruction, and the angularity of the piers/obstruction to the flow direction. For example, using Hydraulics of Bridge Waterways (Bradly, 1978) the approach is:
<ol>
<li>Calculate the ratio of the water area occupied by piers to the gross water area of the constriction (both based on the normal water surface) and the angularity of the piers. These inputs are used to calculate "J" in the FHA documentation.</li>
<li>Use the Figure 4.10 ''Incremental Backwater Coefficient for Piers'' data to calculate Kp. 
[[File:incremental_backwater_coefficient_2018_pier_losses.png]]
 
'''NOTE''': the pier form loss coefficients in Hydraulics of Bridge Waterways are derived based on the cross-sectional averaged velocity through the bridge opening in the absence of piers. It's not necessary to specify a blockage value if a pier form loss coefficient estimated from this method is used.
</li>
</ol>

==Bridge Deck and Rail (Super Structure)==
When a bridge deck become partially or completely submerged, the deck could generate extra afflux resulting in increased water levels and flood extents upstream of the structure. The flow around the deck is highly 3-dimentional and complexed due to the different deck designs/profiles and/or the occurrence of pressure flow. In 2D SWE solver, depth-varying form loss values are often needed to reproduce the afflux caused by such structure. Due to the complexity of the flow, guidelines on how to set the form loss coefficient for the bridge deck are rare. We have carried out a joint research with QLD TMR (Queensland Department of Transport and Main Roads) regarding how to choose a proper form loss value for the bridge deck [https://tuflow.com/media/7554/2022-bridge-deck-afflux-modelling-benchmarking-of-cfd-and-swe-codes-to-real-world-data-collecutt-et-al-hwrs.pdf (Collecutt et al, 2022)] . In the research, CFD modelling was conducted to investigate the characteristics of energy loss of a simple bridge with a flat bottomed deck and guardrails.
 
[[File:CFD_study.png|600px]]

Below are the key findings from the study:
*The results displayed a characteristic shape for head loss coefficient as a function of downstream water level over the deck thickness (TW/T).
*The head loss (afflux) peaks when the water level is approximately 1.6*T above the bridge soffit, and decays slowly as the bridge becomes progressively drowned out.
[[File:FormLoss_vs_TWT.png|600px]]
 

=== Bridge Design (hB/T) vs Form Loss Coefficient Table===
The peak loss coefficient value is a function of the ratio of the depth underneath the deck (hB) and the thickness of the deck (T). This table can be used to estimate the deck form loss coefficient based on the bridge design (hB/T).
<ol>
{| style="text-align: center;" class="wikitable" width="35%"
! style="background-color:#005581; font-weight:bold; color:white;" width=55%| Deck Height to Thickness Ratio
! style="background-color:#005581; font-weight:bold; color:white;" width=45%| Peak Form Loss Coefficient
|-
| Scenario A (hB/T) = 2 || 0.42
|-
| Scenario B (hB/T) = 4 || 0.28
|-
| Scenario C (hB/T) = 6 || 0.20
|}
</ol>

*The solid portion of the guard rails (blockage * rail depth) can be added to T in addition to the deck thickness to calculate hB/T.
*For bridge with more complicated designs (e.g. girders), higher form loss might be required due to the higher surface roughness of the bridge.
*If the hB/T ratio is less than 2 or greater than 6, use a peak form loss coefficient of 0.42 (minimum) or 0.20 (maximum), respectively.

'''NOTE''': This form loss value should not be confused with the value of 1.56 used in the pressure flow approached adopted in [[1D_Bridges | TUFLOW 1D "B" and "BB" bridge]]. TUFLOW 1D bridge pressure flow approach is based on the section 4.13.2 "All Girders in Contact with Flow (Case II)" of ''Guide to Bridge Technology Part 8: Hydraulic Design of Waterway Structures'' (AUSTROADS, 2018). The original hydraulic experiment conducted by [https://hdl.handle.net/10217/39009 Liu et al (1957)] in a laboratory flume with a pair of bridge abutments and a deck. The flow conditions were similar to orifice flow due to the high blockage ratio caused by the abutments and the deck. When modelling bridges in 2D, the contraction/expansion losses caused by the abutments would be handled explicitly by the 2D solver, so a value 1.56 can lead to duplication of the contraction/expansion losses caused by the bridge abutments. 
 

=TUFLOW 2D Bridge Setup=
There are two methods available to model depth varying form loss of a bridge structure:
* [[TUFLOW_2D_Hydraulic_Structures#2D_Layered_Flow_Constriction_.282d_lfcsh.29 |2D Layered Flow Constriction (2d_lfcsh)]]
:The traditional method used to model depth-varying form loss through bridge components such as piers, decks, and rails.

*[[TUFLOW_2D_Hydraulic_Structures#2D_BG_Shape_.282d_bg.29 |2D BG Shape (2d_bg)]] (introduced in the 2023 release)
:A simplified approach developed to simplify the model input based on the findings from the joint TMR Study [https://tuflow.com/media/7554/2022-bridge-deck-afflux-modelling-benchmarking-of-cfd-and-swe-codes-to-real-world-data-collecutt-et-al-hwrs.pdf (Collecutt et al, 2022)].

Both methods provide options for representing flow surcharging, the pressure flow of bridge decks and eventually submerged bridge flow at higher water levels. During the surcharging of bridge decks, higher energy losses can be specified to simulate the pressure flow.

Examples for how to configure both approaches are provided in the 2D structures section of the [[TUFLOW_Example_Models#2D_Structures |TUFLOW Wiki Example Models]] and [[Tutorial_M04 |Tutorial Module 4]] - 2D Bridges.

==2D Layered Flow Constriction (2d_lfcsh)==
Four flow constriction layers are represented in a 2d_lfcsh layer. The lower three layers represents the pier, the bridge deck and the rails. Each layer has its own attributes to specify the blockage and the form loss coefficient. The top (fourth) layer assumes the flow is unimpeded, representative of flow over the top of a bridge. Within the same shape, the invert of the bed, and thickness of each layer can vary in 3D.

The following table provides an overview for how to determine the blockage and form loss coefficient for each layer. Note that this is just an overview and additional guidelines may need to be considered. 
{| style="text-align: left; margin-left: 0; " class="wikitable" width="80%"
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Layer
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Description
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Blockage (%)
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Form Loss Coefficient (FLC)
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Notes
|-

| 1 || Pier layer || ~5% (can be omitted if included in FLC) || Estimate using [[TUFLOW_2D_Hydraulic_Structures#Pier_Losses | Pier Losses]] || Represents flow obstruction from piers beneath the bridge deck
|-
| 2 || Bridge deck || 100% || Use calibration data, if available, to determine FLC. If no calibration is available, estimate using [[TUFLOW_2D_Hydraulic_Structures#Bridge_Design_.28hB.2FT.29_vs_Form_Loss_Coefficient_Table | hB/T vs FLC]] table || Full blockage, no flow through the deck
If using the [[TUFLOW_2D_Hydraulic_Structures#Bridge_Design_.28hB.2FT.29_vs_Form_Loss_Coefficient_Table | hB/T vs FLC]] table, it is recommended to enable the Method C Form Loss Approach
|-
| 3 || Bridge rails || 10% – 100% || Use calibration data, if available, to determine FLC. 
If no calibration data is available, combined FLC for Layers 2 and 3 should be estimated using the [[TUFLOW_2D_Hydraulic_Structures#Bridge_Design_.28hB.2FT.29_vs_Form_Loss_Coefficient_Table | hB/T vs FLC]] table, where T = L2_Depth + (pBlockage × L3_Depth)
*(pBlockage × L3_Depth) represents the solid portion of the rails
*L2 FLC and L3 FLC should sum to the combined FLC
|Blockage and FLC depends on rail type Sensitivity testing with 100% blockage is recommended due to potential for debris during flood
If using the [[TUFLOW_2D_Hydraulic_Structures#Bridge_Design_.28hB.2FT.29_vs_Form_Loss_Coefficient_Table | hB/T vs FLC]] table, it is recommended to enable the Method C Form Loss Approach
|-
| 4 || Above rails || 0% || 0 || Represents unimpeded overtopping flow
|}
<ol>
[[File:2d_lfcsh_attributes.png | 500px ]]
</ol>
 

===Blockage===

The 2d_lfcsh functions by adjusting the flow width and the form loss of 2D cell faces. The combined blockage across the 4 layers is calculated at each simulation timesteps:
<ol>
 
[[File: Blockage_total_equation_01.png|600px]]
 
where 
'''''yi''''' is the actual depth of water in layer '''''i''''' 
'''''ytotal''''' is the total water depth 
</ol>

===Form Loss Approach===

The combined form loss coefficient is determined using one of three methods. The form loss coefficient method can be specified either individually using the 2d_lfcsh “Shape_Options” attribute or globally using the .tcf command: 
<tt>Layered FLC Default Approach == [ METHOD A | {METHOD B} | METHOD C | METHOD D]</tt> 

:METHOD A: The losses are accumulated as the water level rises through the layers. 
<ol>
[[File:Eq_flc_cumulate.png |450px]]
</ol>
:*Layer 1: Constant form loss (L1_FLC)
:*Layers 2 & 3: Form loss increases based on the depth of water in layer 2 & 3; peak form loss at top of Layer 3
:*Above Layer 3: Applies the full accumulated form loss continuously, even when overtopping begins (no reduction)
:Note: Simpler method but tends to overestimate losses when the structure is submerged or overtopped 

:METHOD B (default): the losses are applied pro-rata according to the depth of water in each layer. 
<ol>
[[File:Eq_flc_portion.png |430px]]
</ol>
:*Layer 1: Constant form loss (L1_FLC)
:*Layers 2 & 3: Form loss increases based on the depth of water in layer 2 & 3; peak form loss at top of Layer 3
:*Above Layer 3: Total form loss gradually reduces as water overtops the structure
:Note: Maintains backward compatibility but may underrepresent losses during pressurised or overtopped flows 

:METHOD C (recommended): hybrid approach combining Method A and Method B. 
<ol>
[[File:Eq_flc_methodC.png |520px]]
</ol>
:*Layer 1: Constant form loss (L1_FLC)
:*Layers 2 & 3: Gradual increase in form loss with water level, following Method A
:*Above Layer 3: Total form loss gradually reduces as water overtops the structure, following Method B
:Note: Recommended method; aligns closest to CFD modelling results and TUFLOW HPC behaviour.

:METHOD D: Allows the modeller to control the depth at which the losses start to reduce when the flow transitions between pressure flow and drowned flow.
:This approach is the same used by the 2d_bg layer (introduced in the 2023-03 release). It is recommended to use the 2d_bg layer as it has the benefit of a simplified attribute table, for easier user input.

===Form Loss Calibration Example - Iowa River Flood Study===

In this study, a combined form loss coefficient of 0.35 was used to match observed head loss during slight overtopping of a bridge. The FLC values for each layer were adjusted to achieve the correct combined form loss. The table and plot show how each layer contributes to the total form loss and highlight the differences in calculated form loss between the three methods.

{| style="text-align: left; margin-left: 0;" class="wikitable" width="60%"
!colspan="1" rowspan="2" style="background-color:#005581; font-weight:bold; color:white;" width=6%| Layer
!colspan="1" rowspan="2" style="background-color:#005581; font-weight:bold; color:white;" width=10%| Depth (m)
!colspan="1" rowspan="2" style="background-color:#005581; font-weight:bold; color:white;" width=12%| Blockage (%)
!colspan="2" style="background-color:#005581; font-weight:bold; color:white;" width=20%| Method A
!colspan="2" style="background-color:#005581; font-weight:bold; color:white;" width=20%| Method B
!colspan="2" style="background-color:#005581; font-weight:bold; color:white;" width=20%| Method C
|-
! style="background-color:#005581; font-weight:bold; color:white;"| Layer FLC
! style="background-color:#005581; font-weight:bold; color:white;"| Combined FLC
! style="background-color:#005581; font-weight:bold; color:white;"| Layer FLC
! style="background-color:#005581; font-weight:bold; color:white;"| Combined FLC
! style="background-color:#005581; font-weight:bold; color:white;"| Layer FLC
! style="background-color:#005581; font-weight:bold; color:white;"| Combined FLC
|-
| 1 || 5.0 || 5 || 0.07 || 0.07 || 0.07 || 0.07 || 0.07 || 0.07
|-
| 2 || 1.5 || 100 || 0.15 || 0.22 || 1.05 || 0.30 || 0.15 || 0.22
|-
| 3 || 1.0 || 50 || 0.13 || 0.35 || 0.70 || 0.35 || 0.13 || 0.35
|}

</ol>
 
<ol>
[[File:FLC_vs_height_updated.png | 600px ]]
</ol>

==2D BG Shape (2d_bg)==
2D BG Shape is similar to the Layered Flow Constriction, but has several updates to simplify the input based on the findings from the joint study with TMR [https://tuflow.com/media/7554/2022-bridge-deck-afflux-modelling-benchmarking-of-cfd-and-swe-codes-to-real-world-data-collecutt-et-al-hwrs.pdf (Collecutt et al, 2022)].

The following table provides an overview of how to determine the blockage and form loss coefficient for each layer. Note that this is just an overview and additional guidelines may need to be considered. 
{| style="text-align: left; margin-left: 0; " class="wikitable" width="80%"
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Layer
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Description
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Blockage (%)
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Form Loss Coefficient (FLC)
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Notes
|-

| 1 || Pier layer || ~5% (can be omitted if included in FLC) || Estimate using [[TUFLOW_2D_Hydraulic_Structures#Pier_Losses | Pier Losses]] || Represents flow obstruction from piers beneath the bridge deck
|-
| 2 || Bridge deck || 100% || rowspan="2" | The Super Structure (Super_S) is the bridge deck and rails layers combined. 
Use calibration data, if available, to determine FLC. 
If no calibration data is available, the Super_S FLC should be estimated using the [[TUFLOW_2D_Hydraulic_Structures#Bridge_Design_.28hB.2FT.29_vs_Form_Loss_Coefficient_Table | hB/T vs FLC]] table, where T = Deck_Depth + (Rail_pBlockage*Rail_Depth)
*(Rail_pBlockage*Rail_Depth) represents the solid portion of the rails
|| Full blockage, no flow through the deck
|-
| 3 || Bridge rails || 10% – 100% || Sensitivity testing with 100% blockage is recommended due to potential for debris during flood events
|-
| 4 || Above rails || 0% || 0 || Represents unimpeded overtopping flow
|}

<ol>
[[File:Bridge block.jpg | 800px]]
</ol>

===Inflection Point===

Based on findings from the joint study [https://tuflow.com/media/7554/2022-bridge-deck-afflux-modelling-benchmarking-of-cfd-and-swe-codes-to-real-world-data-collecutt-et-al-hwrs.pdf (Collecutt et al, 2022)], the head loss peaks when the water level is approximately 1.6*T above the bridge soffit, and decays slowly as the bridge becomes progressively drowned out. The 'SuperS_IPf' attribute (inflection point factor, default = 1.6) can be used to define the height of the inflection point. The solid portion of the rail layer is also added to the deck thickness to calculate the depth to the inflection point (DIP), i.e.:
<ol>
[[File:eq_flc_bg_infection_point.png | 520px ]]
</ol>

===Form Loss Approach===
The form loss approach is similar to the FLC approach METHOD C, with L2/L3 replaced by a single super structure layer:
<ol>
[[File:eq_flc_bg.png | 480px ]]
</ol>

===Form Loss Calibration Example - Iowa River Flood Study===
This example uses the same bridge setup described in the[[TUFLOW_2D_Hydraulic_Structures#Form_Loss_Calibration_Example_-_Iowa_River_Flood_Study | 2D Layered Flow Constriction]] section, with the following parameters applied:
*SuperS_FLC = 0.28
*SuperS_Ipf = 1.6,
The Depth to Inflection Point (DIP) is calculated as 3.2m above the bridge soffit.

The table and figure below show how the form loss value varies with water depth.
<ol>
{| style="text-align: center;" class="wikitable" width="32%"
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;" width=8%| Layer
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;" width=8%| Depth (m)
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;" width=8%| Blockage (%)
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;" width=8%| Form Loss
|-
| Pier || 5.0 || 5 || 0.07
|-
| Deck || 1.5 || 100 || rowspan="2" | 0.28
|-
| Rail || 1.0 || 50
|}

[[File:FLC_vs_height_bg.png | 600px ]]
</ol>

== 2D Bridges Line vs Polygon Layer ==
The form loss coefficient (FLC) is applied differently when using a line compared to a polygon for both 2d_lfcsh and 2d_bg inputs. The FLC is applied at cell sides (u and v faces) as this is where velocities are calculated. 
For larger bridges that spread across multiple cells, it is recommended to use a polygon layer, which selects all u and v faces falling within the polygon.
 
 
'''2D Layered Flow Constriction (2d_lfcsh)'''
{| style="text-align: left; margin-left: 0;" class="wikitable" width="80%"
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 7.5%;"| Geometry
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 7.5%;"| Line Type
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 11%;"| Width Attribute
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 22%;"| FLC Input
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 22%;"| FLC Applied
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 30%;"| Notes
|-
!rowspan="3" | Line
| Thin
| zero
| Total form loss of the bridge
| Applies the FLC to a single row of cell sides
| This approach is cell size independent. It is the easiest setup and the preferred / recommended approach when using 2d_lfcsh.
|-
| Thick
| between zero and 1.5 times the cell size
| Total form loss of the bridge
| FLC/2 applied to all sides of the selected cells
| A cell is selected if the polyline intersects the cell crosshair. Caution should be taken when using a "thick" line, as changes in cell size can cause it to become a "wide" line. If this occurs, the FLC attribute may need to be recalculated to avoid overestimating or underestimating losses.
|-
| Wide
| larger than 1.5 times the cell size
| Total form loss of the bridge ''(may need to be recalculated, see notes)''
| FLC divided by number of cell sides in the direction of flow 
''(number of cell sides in the direction of flow is calculated as line width divided by cell size)''
| Polygon shapes are recommended if more than 3 rows of faces must be selected.. 
Caution should be taken when using a "wide" line. The cell size and alignment of the 2d_lfcsh line may result in selecting too many or too few cell faces in the direction of the flow. The FLC input may need to be recalculated to ensure FLC Applied multiplied by the number of cell sides in the direction of flow equates to the intended total form loss.
|-
!rowspan="1" | Polygon
| -
| -
| Total loss per unit length (meters or feet) in the direction of flow
| FLC * cell size applied to all sides of selected cells
|
|}

'''2D Bridge (2d_bg)'''
{| style="text-align: left; margin-left: 0;" class="wikitable" width="80%"
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 7.5%;"| Geometry
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 7.5%;"| Line Type
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 11%;"| Width Attribute
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 22%;"| FLC Input
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 22%;"| FLC Applied
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 30%;"| Notes
|-
!rowspan="3" | Line
| Thin
| zero
| Total form loss of the bridge
| Applies the FLC to a single row of cell sides.
| This approach is cell size independent.
|-
| Thick
| larger than zero
| Total form loss of the bridge
| FLC/2 applied to all sides of the selected cells
| This approach is cell size independent. A cell is selected if the polyline intersects the cell crosshair.
|-
| Wide
| Not supported
| –
| –
| BG polygon shapes are recommended if more than 3 rows of faces must be selected.
|-
!rowspan="1" |Polygon
| -
| ''(used to automatically distribute the total FLC to the selected faces)''
| Total form loss of the bridge
| FLC / Deck_Width * cell size applied to all sides of selected cells
| For bridges modelled using a 2d_bg polygon the relative ratio of the bridge width to the 2D cell size should be 4 or greater. For more information on this see [https://downloads.tuflow.com/Other/2d_bg_R_Bridge_Configuration_Advice_202503.pdf 2d_bg_R_Bridge_Configuration_Advice.pdf].
|}
 
The following diagrams demonstrate how the input FLC is applied for the four geometry options for 2d_lfcsh and 2d_bg layers: 
[[File:2dlfcsh 2dbg combined v2.png|1200px]]

It is good modelling practice to check the [[Check_Files_2d_lfcsh_uvpt | lfcsh_uvpt_check]] and [[Check Files 2d bg uvpt check | bg_uvpt_check]] files to confirm the number of faces selected and the FLC values assigned. It is also strongly recommended to undertake a sensitivity analysis on the applied form losses in the model to check if it makes any difference to the results and/or double check against other methods (hand calculations, other software, CFD modelling), especially if the bridge is near an area of interest. If calibration data is available, this should be used to guide the form loss value specification. 
 

= Common Questions Answered (FAQ)=
== What blockage values should I use for bridge guard rails? ==
The blockage of bridge guard rails can be anything from 100% blocked (solid concrete rails) to 10% blocked (very open rails). In addition, the accumulation of debris during a flood can be substantial as shown in the image below. Sensitivity testing with 100% blockage is recommended.
 
[[File:Bridge rail debris.jpg | 500px]]

== How to conduct sensitivity test for 2D bridges? ==
General recommendations to cross-check the results are:
* Compare computed affluxes against desktop methods (e.g. Hydraulics of Bridge Waterways, 1978) and/or other software including CFD, especially for unusual bridge designs.
* Use any recorded flood marks or general observations from past events to check and calibrate FLC values.
* Conduct sensitivity testing by assessing the impact and influence of FLC values on your modelling objectives. The afflux resulting from the FLC values will be proportional to the velocity head, i.e. ∆h=FLC*(v^2/2g). As such, if velocities are low (e.g. 1 m/s), the results may not be overly sensitive to uncertainties in the FLC values. If completing a check using this equation for a long skew bridge it is best to calculate the total structure velocity from a PO line digitised in the same location as the bridge.

Finally, after completing sensitivity testing and understanding the range of uncertainty due to unknowns like the degree of blockage and influence of FLC values (e.g. +/-20%), you are in a position to discuss with your client how best to proceed. For example, if the modelling is to set planning levels for a development upstream then it may be appropriate to choose values on the higher side (higher FLC values and/or blockage assumptions), noting that the uncertainty may be amply covered by a regulatory freeboard. Conversely, if the development is on the downstream side the conservative approach would be to use the results at the lower end of your FLC/blockage values. 
[[File:Bridge Flood Debris Loading.jpg | 500px]] 

== Should I use both FLC and blockage for layer one in 2D bridge layered flow constriction? ==
When applying FLC and blockage values to model obstructions such as piers, the following considerations need to be taken into account:
* The FLC value applies an energy loss along 1D channels or across 2D cell faces equivalent to FLC*V2/2g where V is the 1D channel velocity or the 2D cell face velocity.
* FLC values are often sourced from publications such as Hydraulics of Bridge Waterways or AustRoads (e.g. Kp chart for piers).
* If possible, establish whether the source of the FLC value is based on the approach velocity (the velocity in the absence of piers) or structure velocity (the velocity with area blocked out by the piers) noting that it often isn’t clear or stated.
** If it is the structure velocity, this is usually the velocity at the vena-contracta (point of greatest contraction within the entrance to the structure and therefore highest velocity) - see image below. Bluff or sharp-edged obstructions will have a much more pronounced vena-contracta, and therefore higher velocity compared with a round-edged obstruction.
** FLC values based on the approach velocity will be higher than those based on the structure velocity to achieve the same energy loss.
* Applying a blockage equivalent to the obstruction width will increase, usually very slightly, the velocity of the 1D channel or 2D cell face. This won’t be the vena-contracta velocity, but a velocity between the approach velocity and the vena-contracta velocity. A greater blockage will need to be applied to emulate the vena-contracta velocity.
* If the FLC source value is based on:
** The approach velocity then there is no need to apply a blockage value.
** The structure velocity then the blockage value should be applied noting that it may be appropriate to apply a larger blockage to take into account the vena-contracta.
* If it is not clear or unknown whether the FLC source value is based on the approach or structure velocity, the recommendation would be to apply the blockage in the interests of being slightly conservative on the upstream flood level calculation.
* For most minor obstructions such as bridge piers, the blockage is usually relatively small and whether included or not has a negligible or minor affect on flood levels compared with other factors such as the approach embankments and the bridge deck.
* Blockage from debris wrapped around piers can have a greater influence on the results than the effect of applying or not applying a blockage. Debris wrapped around piers can be accounted for in the FLC value calculated for the pier layer.
* As always, sensitivity testing with and without blockage and +/- the FLC value is highly recommended to understand their importance in regard to the broader modelling objectives and the effects of uncertainties in the input data, boundaries, other parameters such as Manning’s n values, and the accuracy of the numerical solution scheme (see [https://www.tuflow.com/library/webinars/#maximise_accuracy Maximising the Accuracy of Hydraulic Models webinar]).
[[File: Vena_contracta.png]] 
''Image showing the formation of the vena-contracta.'' 
 

==I don't see results that I expect when using 2d_lfcsh layer==
The 2d_lfcsh layer is a versatile feature that was designed to model bridges in 2D, but can also be used for other applications like fences, buildings raised on pillars and so on.
Some of the unexpected results could be:
* Water level going through the bridge deck in 2D map output.
* Water transiting through 100% blocked Layer 1, e.g. fences with solid base.
* SHMax.csv reporting values above the bridge deck when 2D map output reports water level lower than the top of the bridge deck.

TUFLOW is a 2D solution (not 3D), in the 2d_lfcsh layer the percent blockage and form loss coefficient applied to the cell faces is depth averaged across the entire cell face (across Layer 1, 2 and 3): 
*For bridges, where Layer 2 has a 100% blockage applied, the minimum flow width of 0.001m is used and is averaged with the Layer 1 blockage (based on the depth of the water). This may result in a water level being reported within or above the bridge deck, which would represent the pressure head.
*Layered flow constriction works by adjusting the flow area of the cell faces by any blockages to generate the correct depth averaged velocity at each face at which the form losses are applied as a fraction of the V2/2g kinetic energy. Calculating the correct velocity is critical for determining the losses as the losses are proportional to the velocity squared. 
*For a layered flow constriction cell face the flow area cannot be zero above the invert of Layer 1 to avoid a divide by zero in the computations, therefore a minimum average flow width after applying blockages of 0.001 m is applied. if Layer 1 is 100% blocked, a very small amount of water will flow through Layer 1. If this is unacceptable, instead of applying 100% blockage of Layer 1, the preferred approach is to start the layered flow constriction at the top of Layer 1 or raise the ground elevation to the top of Layer 1 using one of the Z Shape modification functions (e.g. a breakline). 
<ol>
[[File:100% Blockage Diagram.png | 500px]]
</ol>

== Can I model bridge piers explicitly in 2D using very small cells? ==
It isn't recommended to explicitly model bridge piers by blocking out the pier faces in TUFLOW, or in any hydraulic modelling software based on solving Shallow Water Equations(SWE). Due to the 3-dimentiality of the flow and turbulence around a pier, computational fluid dynamics (CFD) approach is often required to simulate the flow around piers explicitly. The wake turbulence behind a simple-shape pier can be resolved to some extent using extremely fine mesh in TUFLOW (see calibration example to a flume experiment in the [https://www.tuflow.com/library/webinars/#structures webinar on Energy Losses at Structures]), however the predictions for head losses show notable sensitivities to the mesh size, the mesh design, and the choice of turbulence model. The extremely fine mesh resolution also results in significantly higher computational costs.

Therefore, the safest and strongly recommended approach with regard to establishing head losses and consequently flood levels, is to model the effects of such obstructions with form loss coefficients (applied to selected mesh cells) that have been derived from physical testing. This approach has been shown to provide the most consistent results across various mesh resolutions. It also has the added benefit that, by avoiding small cells in the mesh, it will provide much more efficient run times for flow solvers.

[[File:Flow round a cylinder.png]]

''The point of flow separation around an object has a major bearing on the drag coefficient and is not reliably reproduced by 2D or 3D software.''


== How to best convert flow constriction data (2d_fc or 2d_fcsh) into newer formats (2d_lfcsh or 2d_bg)? ==
The form loss parameters can be transferred from the flow constriction (2d_fc or 2d_fcsh) to the first layer of the layered flow constriction (2d_lfcsh) or pier layer of the 2d_bg. Definition of the remaining form loss and blockage layer inputs should follow the guidance outlined in [[TUFLOW_2D_Hydraulic_Structures#2D_Layered_Flow_Constriction_.282d_lfcsh.29 | 2D Layered Flow Constriction]] and [[TUFLOW_2D_Hydraulic_Structures#2D_BG_Shape_.282d_bg.29 | 2D BG Shape]] paragraphs. 
When using floating pontoon (type FD in the 2d_fc or 2d_fcsh) different setup might need to be used for different events. For large events when floating pontoon becomes fixed at the top of the supporting piles, standard 2d_lfcsh setup can be used. Smaller events when the pontoon is floating at different heights might require more sensitivity testing of the structure parameters to find out a setup the matches the reality as close as possible. 

== Should I model bridges in 1D or 2D Domain? ==
The recommended approach typically depends on the study objectives and if the channel upstream and downstream of the bridge is modelled in 1D or 2D. To preserve the momentum as accurately as possible the bridge should be modelled in the same dimension as the channel, e.g. 1d_nwk bridge if the channels is in 1D and 2d_bg or 2d_lfcsh if the channel is modelled in 2D. 
In 2D, the expansion/contraction losses are modelled based on the topography and don't need to be estimated as attributes as for 1D modelling. Also, for higher flows where the bridge is overtopped, 2D is preferable approach.

== What is the difference between downstream and upstream controlled flow? ==
Downstream control means a change in downstream water level will cause a change in upstream water level. Upstream control means the upstream water level is insensitive to the downstream water level and usually indicates the occurrence of supercritical flow.

== What FLC values should be used for 2d_bg bridge if hB/T is below 2 or above 6? ==
TMR has extended the CFD simulation to hB/T ratios of 1 to 10. Refer to the [https://docs.tuflow.com/classic-hpc/manual/latest/ TUFLOW Manual] for details.

If hB/T is outside this ratio:
* hB/T ratios of less than 1 represent a very unusual bridge sitting low to the ground, and the peak FLC may increase above the end value (FLC of 0.6) in a way that doesn't follow the research trend or extrapolation. For these cases we would recommend using CFD modelling to obtain a more informed value. Alternatively, computing an FLC based on pressure flow or using 1D culvert might be considered.
* For hB/T ratios of greater than 10, the FLC is likely to continue to decrease, but probably not significantly. Clamping to the end value (FLC of 0.16) might be considered the more conservative approach (if the primary concern is flood levels upstream of the bridge). 
 
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TUFLOW 2D Hydraulic Structures

2026-04-10T02:03:08Z

Emilie Nielsen: /* 2D Layered Flow Constriction (2d_lfcsh) */

= 2D Structure Modelling Theory =
The theory behind the modelling of energy losses and affluxes of hydraulic structures is presented in the following webinars by Bill Syme and Greg Collecutt (TUFLOW Developers).

*[https://www.tuflow.com/library/webinars/#structures Webinar Link: Modelling Energy Losses at Structures] 
*[https://www.tuflow.com/library/webinars/#nov2022_hydraulic_modelling_bridge Webinar Link: 1D, 2D & 3D Hydraulic Modelling of Bridges]
 

= 2D Bridge Modelling in TUFLOW - Overview =
The TUFLOW 2D solution explicitly predicts the majority of “macro” losses due to the expansion and contraction of water through a constriction, or around a bend, provided the resolution of the grid is sufficiently fine ([https://www.tuflow.com/Download/Publications/Flow%20Through%20an%20Abrupt%20Constriction%20-%202D%20Hydrodynamic%20Performance%20and%20Influence%20of%20Spatial%20Resolution,%20Barton,%202001.pdf Barton, 2001]; [https://www.tuflow.com/Download/Publications/Modelling%20of%20Bends%20and%20Hydraulic%20Structures%20in%20a%202D%20Scheme,%20Syme,%202001.pdf Syme, 2001]; [https://www.tuflow.com/Download/Technical_Memos/Modelling%20Bridge%20Piers%20in%202D%20using%20TUFLOW.pdf Ryan, 2013]). Where the 2D model is not of fine enough resolution to simulate the “micro” losses (e.g. from bridge piers, vena contracta, losses in the vertical (3rd) dimension), additional form loss coefficients and/or modifications to the cells widths and flow height need to be added.
==Contraction/Expansion Losses (“Macro” Losses)==
Loss of energy is caused by the flow contraction during the expansion of water after the vena-contracta inside a bridge section and the flow expansion downstream a bridge. As discussed above, this type of "macro" losses can be explicitly resolved by the TUFLOW 2D solver, provided that a proper turbulence model and mesh size are used. Below is an example of the 2D modelling of flow contraction/expansion at a pair of bridge abutments.
 
[[File:FC_Velocity_Example.PNG|600px]] 

==Pier Losses==
Piers are usually smaller than the 2D cell size in real-world flood models. Although flexible mesh solver or quadtree refinement can be applied to reduce the local cell size around the pier, it also comes with an expensive computational cost that could significantly increase the simulation time. More practically, the backwater effect of piers can be modelled as sub-grid form losses.

Pier form loss coefficients can be derived from information in publications such as [https://www.fhwa.dot.gov/engineering/hydraulics/library_arc.cfm?pub_number=1&id=5 ''Hydraulics of Bridge Waterways'' (Bradly, 1978)] or [https://austroads.com.au/publications/bridges/agbt08 ''Guide to Bridge Technology Part 8: Hydraulic Design of Waterway Structures'' (AUSTROADS, 2018)]. Energy loss estimated from bridge piers or other obstructions, vertical or horizontal, that do not cause upstream controlled flow regimes like pressure flow, are dependent on the ratio of the obstruction's area perpendicular to the flow direction to the gross flow area of the bridge opening, the shape of the piers or obstruction, and the angularity of the piers/obstruction to the flow direction. For example, using Hydraulics of Bridge Waterways (Bradly, 1978) the approach is:
<ol>
<li>Calculate the ratio of the water area occupied by piers to the gross water area of the constriction (both based on the normal water surface) and the angularity of the piers. These inputs are used to calculate "J" in the FHA documentation.</li>
<li>Use the Figure 4.10 ''Incremental Backwater Coefficient for Piers'' data to calculate Kp. 
[[File:incremental_backwater_coefficient_2018_pier_losses.png]]
 
'''NOTE''': the pier form loss coefficients in Hydraulics of Bridge Waterways are derived based on the cross-sectional averaged velocity through the bridge opening in the absence of piers. It's not necessary to specify a blockage value if a pier form loss coefficient estimated from this method is used.
</li>
</ol>

==Bridge Deck and Rail (Super Structure)==
When a bridge deck become partially or completely submerged, the deck could generate extra afflux resulting in increased water levels and flood extents upstream of the structure. The flow around the deck is highly 3-dimentional and complexed due to the different deck designs/profiles and/or the occurrence of pressure flow. In 2D SWE solver, depth-varying form loss values are often needed to reproduce the afflux caused by such structure. Due to the complexity of the flow, guidelines on how to set the form loss coefficient for the bridge deck are rare. We have carried out a joint research with QLD TMR (Queensland Department of Transport and Main Roads) regarding how to choose a proper form loss value for the bridge deck [https://tuflow.com/media/7554/2022-bridge-deck-afflux-modelling-benchmarking-of-cfd-and-swe-codes-to-real-world-data-collecutt-et-al-hwrs.pdf (Collecutt et al, 2022)] . In the research, CFD modelling was conducted to investigate the characteristics of energy loss of a simple bridge with a flat bottomed deck and guardrails.
 
[[File:CFD_study.png|600px]]

Below are the key findings from the study:
*The results displayed a characteristic shape for head loss coefficient as a function of downstream water level over the deck thickness (TW/T).
*The head loss (afflux) peaks when the water level is approximately 1.6*T above the bridge soffit, and decays slowly as the bridge becomes progressively drowned out.
[[File:FormLoss_vs_TWT.png|600px]]
 

=== Bridge Design (hB/T) vs Form Loss Coefficient Table===
The peak loss coefficient value is a function of the ratio of the depth underneath the deck (hB) and the thickness of the deck (T). This table can be used to estimate the deck form loss coefficient based on the bridge design (hB/T).
<ol>
{| style="text-align: center;" class="wikitable" width="35%"
! style="background-color:#005581; font-weight:bold; color:white;" width=55%| Deck Height to Thickness Ratio
! style="background-color:#005581; font-weight:bold; color:white;" width=45%| Peak Form Loss Coefficient
|-
| Scenario A (hB/T) = 2 || 0.42
|-
| Scenario B (hB/T) = 4 || 0.28
|-
| Scenario C (hB/T) = 6 || 0.20
|}
</ol>

*The solid portion of the guard rails (blockage * rail depth) can be added to T in addition to the deck thickness to calculate hB/T.
*For bridge with more complicated designs (e.g. girders), higher form loss might be required due to the higher surface roughness of the bridge.
*If the hB/T ratio is less than 2 or greater than 6, use a peak form loss coefficient of 0.42 (minimum) or 0.20 (maximum), respectively.

'''NOTE''': This form loss value should not be confused with the value of 1.56 used in the pressure flow approached adopted in [[1D_Bridges | TUFLOW 1D "B" and "BB" bridge]]. TUFLOW 1D bridge pressure flow approach is based on the section 4.13.2 "All Girders in Contact with Flow (Case II)" of ''Guide to Bridge Technology Part 8: Hydraulic Design of Waterway Structures'' (AUSTROADS, 2018). The original hydraulic experiment conducted by [https://hdl.handle.net/10217/39009 Liu et al (1957)] in a laboratory flume with a pair of bridge abutments and a deck. The flow conditions were similar to orifice flow due to the high blockage ratio caused by the abutments and the deck. When modelling bridges in 2D, the contraction/expansion losses caused by the abutments would be handled explicitly by the 2D solver, so a value 1.56 can lead to duplication of the contraction/expansion losses caused by the bridge abutments. 
 

=TUFLOW 2D Bridge Setup=
There are two methods available to model depth varying form loss of a bridge structure:
* [[TUFLOW_2D_Hydraulic_Structures#2D_Layered_Flow_Constriction_.282d_lfcsh.29 |2D Layered Flow Constriction (2d_lfcsh)]]
:The traditional method used to model depth-varying form loss through bridge components such as piers, decks, and rails.

*[[TUFLOW_2D_Hydraulic_Structures#2D_BG_Shape_.282d_bg.29 |2D BG Shape (2d_bg)]] (introduced in the 2023 release)
:A simplified approach developed to simplify the model input based on the findings from the joint TMR Study [https://tuflow.com/media/7554/2022-bridge-deck-afflux-modelling-benchmarking-of-cfd-and-swe-codes-to-real-world-data-collecutt-et-al-hwrs.pdf (Collecutt et al, 2022)].

Both methods provide options for representing flow surcharging, the pressure flow of bridge decks and eventually submerged bridge flow at higher water levels. During the surcharging of bridge decks, higher energy losses can be specified to simulate the pressure flow.

Examples for how to configure both approaches are provided in the 2D structures section of the [[TUFLOW_Example_Models#2D_Structures |TUFLOW Wiki Example Models]] and [[Tutorial_M04 |Tutorial Module 4]] - 2D Bridges.

==2D Layered Flow Constriction (2d_lfcsh)==
Four flow constriction layers are represented in a 2d_lfcsh layer. The lower three layers represents the pier, the bridge deck and the rails. Each layer has its own attributes to specify the blockage and the form loss coefficient. The top (fourth) layer assumes the flow is unimpeded, representative of flow over the top of a bridge. Within the same shape, the invert of the bed, and thickness of each layer can vary in 3D.

The following table provides an overview for how to determine the blockage and form loss coefficient for each layer. Note that this is just an overview and additional guidelines may need to be considered. 
{| style="text-align: left; margin-left: 0; " class="wikitable" width="80%"
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Layer
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Description
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Blockage (%)
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Form Loss Coefficient (FLC)
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Notes
|-

| 1 || Pier layer || ~5% (can be omitted if included in FLC) || Estimate using [[TUFLOW_2D_Hydraulic_Structures#Pier_Losses | Pier Losses]] || Represents flow obstruction from piers beneath the bridge deck
|-
| 2 || Bridge deck || 100% || Use calibration data, if available, to determine FLC. If no calibration is available, estimate using [[TUFLOW_2D_Hydraulic_Structures#Bridge_Design_.28hB.2FT.29_vs_Form_Loss_Coefficient_Table | hB/T vs FLC]] table || Full blockage, no flow through the deck
If using the [[TUFLOW_2D_Hydraulic_Structures#Bridge_Design_.28hB.2FT.29_vs_Form_Loss_Coefficient_Table | hB/T vs FLC]] table, it is recommended to enable the Method C Form Loss Approach
|-
| 3 || Bridge rails || 10% – 100% || Use calibration data, if available, to determine FLC. 
If no calibration data is available, combined FLC for Layers 2 and 3 should be estimated using the [[TUFLOW_2D_Hydraulic_Structures#Bridge_Design_.28hB.2FT.29_vs_Form_Loss_Coefficient_Table | hB/T vs FLC]] table, where T = L2_Depth + (pBlockage × L3_Depth)
*(pBlockage × L3_Depth) represents the solid portion of the rails
*L2 FLC and L3 FLC should sum to the combined FLC
|Blockage and FLC depends on rail type Sensitivity testing with 100% blockage is recommended due to potential for debris during flood
If using the [[TUFLOW_2D_Hydraulic_Structures#Bridge_Design_.28hB.2FT.29_vs_Form_Loss_Coefficient_Table | hB/T vs FLC]] table, it is recommended to enable the Method C Form Loss Approach
|-
| 4 || Above rails || 0% || 0 || Represents unimpeded overtopping flow
|}
<ol>
[[File:2d_lfcsh_attributes.png | 500px ]]
</ol>
 

===Blockage===

The 2d_lfcsh functions by adjusting the flow width and the form loss of 2D cell faces. The combined blockage across the 4 layers is calculated at each simulation timesteps:
<ol>
 
[[File: Blockage_total_equation_01.png|600px]]
 
where 
'''''yi''''' is the actual depth of water in layer '''''i''''' 
'''''ytotal''''' is the total water depth 
</ol>

===Form Loss Approach===

The combined form loss coefficient is determined using one of three methods. The form loss coefficient method can be specified either individually using the 2d_lfcsh “Shape_Options” attribute or globally using the .tcf command: 
<tt>Layered FLC Default Approach == [ METHOD A | {METHOD B} | METHOD C | METHOD D]</tt> 

:METHOD A: The losses are accumulated as the water level rises through the layers. 
<ol>
[[File:Eq_flc_cumulate.png |450px]]
</ol>
:*Layer 1: Constant form loss (L1_FLC)
:*Layers 2 & 3: Form loss increases based on the depth of water in layer 2 & 3; peak form loss at top of Layer 3
:*Above Layer 3: Applies the full accumulated form loss continuously, even when overtopping begins (no reduction)
:Note: Simpler method but tends to overestimate losses when the structure is submerged or overtopped 

:METHOD B (default): the losses are applied pro-rata according to the depth of water in each layer. 
<ol>
[[File:Eq_flc_portion.png |430px]]
</ol>
:*Layer 1: Constant form loss (L1_FLC)
:*Layers 2 & 3: Form loss increases based on the depth of water in layer 2 & 3; peak form loss at top of Layer 3
:*Above Layer 3: Total form loss gradually reduces as water overtops the structure
:Note: Maintains backward compatibility but may underrepresent losses during pressurised or overtopped flows 

:METHOD C (recommended): hybrid approach combining Method A and Method B. 
<ol>
[[File:Eq_flc_methodC.png |520px]]
</ol>
:*Layer 1: Constant form loss (L1_FLC)
:*Layers 2 & 3: Gradual increase in form loss with water level, following Method A
:*Above Layer 3: Total form loss gradually reduces as water overtops the structure, following Method B
:Note: Recommended method; aligns closest to CFD modelling results and TUFLOW HPC behaviour.

:METHOD D: Allows the modeller to control the depth at which the losses start to reduce when the flow transitions between pressure flow and drowned flow.
:This approach is the same used by the 2d_bg layer (introduced in the 2023-03 release). It is recommended to use the 2d_bg layer as it has the benefit of a simplified attribute table, for easier user input.

===Form Loss Calibration Example - Iowa River Flood Study===

In this study, a combined form loss coefficient of 0.35 was used to match observed head loss during slight overtopping of a bridge. The FLC values for each layer were adjusted to achieve the correct combined form loss. The table and plot show how each layer contributes to the total form loss and highlight the differences in calculated form loss between the three methods.

{| style="text-align: left; margin-left: 0;" class="wikitable" width="60%"
!colspan="1" rowspan="2" style="background-color:#005581; font-weight:bold; color:white;" width=6%| Layer
!colspan="1" rowspan="2" style="background-color:#005581; font-weight:bold; color:white;" width=10%| Depth (m)
!colspan="1" rowspan="2" style="background-color:#005581; font-weight:bold; color:white;" width=12%| Blockage (%)
!colspan="2" style="background-color:#005581; font-weight:bold; color:white;" width=20%| Method A
!colspan="2" style="background-color:#005581; font-weight:bold; color:white;" width=20%| Method B
!colspan="2" style="background-color:#005581; font-weight:bold; color:white;" width=20%| Method C
|-
! style="background-color:#005581; font-weight:bold; color:white;"| Layer FLC
! style="background-color:#005581; font-weight:bold; color:white;"| Combined FLC
! style="background-color:#005581; font-weight:bold; color:white;"| Layer FLC
! style="background-color:#005581; font-weight:bold; color:white;"| Combined FLC
! style="background-color:#005581; font-weight:bold; color:white;"| Layer FLC
! style="background-color:#005581; font-weight:bold; color:white;"| Combined FLC
|-
| 1 || 5.0 || 5 || 0.07 || 0.07 || 0.07 || 0.07 || 0.07 || 0.07
|-
| 2 || 1.5 || 100 || 0.15 || 0.22 || 1.05 || 0.30 || 0.15 || 0.22
|-
| 3 || 1.0 || 50 || 0.13 || 0.35 || 0.70 || 0.35 || 0.13 || 0.35
|}

</ol>
 
<ol>
[[File:FLC_vs_height_updated.png | 600px ]]
</ol>

==2D BG Shape (2d_bg)==
2D BG Shape is similar to the Layered Flow Constriction, but has several updates to simplify the input based on the findings from the joint study with TMR [https://tuflow.com/media/7554/2022-bridge-deck-afflux-modelling-benchmarking-of-cfd-and-swe-codes-to-real-world-data-collecutt-et-al-hwrs.pdf (Collecutt et al, 2022)].

The following table provides an overview of how to determine the blockage and form loss coefficient for each layer: 
{| style="text-align: left; margin-left: 0; " class="wikitable" width="80%"
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Layer
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Description
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Blockage (%)
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Form Loss Coefficient (FLC)
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Notes
|-

| 1 || Pier layer || ~5% (can be omitted if included in FLC) || Estimate using [[TUFLOW_2D_Hydraulic_Structures#Pier_Losses | Pier Losses]] || Represents flow obstruction from piers beneath the bridge deck
|-
| 2 || Bridge deck || 100% || rowspan="2" | The Super Structure (Super_S) is the bridge deck and rails layers combined. 
Use calibration data, if available, to determine FLC. 
If no calibration data is available, the Super_S FLC should be estimated using the [[TUFLOW_2D_Hydraulic_Structures#Bridge_Design_.28hB.2FT.29_vs_Form_Loss_Coefficient_Table | hB/T vs FLC]] table, where T = Deck_Depth + (Rail_pBlockage*Rail_Depth)
*(Rail_pBlockage*Rail_Depth) represents the solid portion of the rails
|| Full blockage, no flow through the deck
|-
| 3 || Bridge rails || 10% – 100% || Sensitivity testing with 100% blockage is recommended due to potential for debris during flood events
|-
| 4 || Above rails || 0% || 0 || Represents unimpeded overtopping flow
|}

<ol>
[[File:Bridge block.jpg | 800px]]
</ol>

===Inflection Point===

Based on findings from the joint study [https://tuflow.com/media/7554/2022-bridge-deck-afflux-modelling-benchmarking-of-cfd-and-swe-codes-to-real-world-data-collecutt-et-al-hwrs.pdf (Collecutt et al, 2022)], the head loss peaks when the water level is approximately 1.6*T above the bridge soffit, and decays slowly as the bridge becomes progressively drowned out. The 'SuperS_IPf' attribute (inflection point factor, default = 1.6) can be used to define the height of the inflection point. The solid portion of the rail layer is also added to the deck thickness to calculate the depth to the inflection point (DIP), i.e.:
<ol>
[[File:eq_flc_bg_infection_point.png | 520px ]]
</ol>

===Form Loss Approach===
The form loss approach is similar to the FLC approach METHOD C, with L2/L3 replaced by a single super structure layer:
<ol>
[[File:eq_flc_bg.png | 480px ]]
</ol>

===Form Loss Calibration Example - Iowa River Flood Study===
This example uses the same bridge setup described in the[[TUFLOW_2D_Hydraulic_Structures#Form_Loss_Calibration_Example_-_Iowa_River_Flood_Study | 2D Layered Flow Constriction]] section, with the following parameters applied:
*SuperS_FLC = 0.28
*SuperS_Ipf = 1.6,
The Depth to Inflection Point (DIP) is calculated as 3.2m above the bridge soffit.

The table and figure below show how the form loss value varies with water depth.
<ol>
{| style="text-align: center;" class="wikitable" width="32%"
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;" width=8%| Layer
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;" width=8%| Depth (m)
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;" width=8%| Blockage (%)
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;" width=8%| Form Loss
|-
| Pier || 5.0 || 5 || 0.07
|-
| Deck || 1.5 || 100 || rowspan="2" | 0.28
|-
| Rail || 1.0 || 50
|}

[[File:FLC_vs_height_bg.png | 600px ]]
</ol>

== 2D Bridges Line vs Polygon Layer ==
The form loss coefficient (FLC) is applied differently when using a line compared to a polygon for both 2d_lfcsh and 2d_bg inputs. The FLC is applied at cell sides (u and v faces) as this is where velocities are calculated. 
For larger bridges that spread across multiple cells, it is recommended to use a polygon layer, which selects all u and v faces falling within the polygon.
 
 
'''2D Layered Flow Constriction (2d_lfcsh)'''
{| style="text-align: left; margin-left: 0;" class="wikitable" width="80%"
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 7.5%;"| Geometry
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 7.5%;"| Line Type
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 11%;"| Width Attribute
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 22%;"| FLC Input
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 22%;"| FLC Applied
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 30%;"| Notes
|-
!rowspan="3" | Line
| Thin
| zero
| Total form loss of the bridge
| Applies the FLC to a single row of cell sides
| This approach is cell size independent. It is the easiest setup and the preferred / recommended approach when using 2d_lfcsh.
|-
| Thick
| between zero and 1.5 times the cell size
| Total form loss of the bridge
| FLC/2 applied to all sides of the selected cells
| A cell is selected if the polyline intersects the cell crosshair. Caution should be taken when using a "thick" line, as changes in cell size can cause it to become a "wide" line. If this occurs, the FLC attribute may need to be recalculated to avoid overestimating or underestimating losses.
|-
| Wide
| larger than 1.5 times the cell size
| Total form loss of the bridge ''(may need to be recalculated, see notes)''
| FLC divided by number of cell sides in the direction of flow 
''(number of cell sides in the direction of flow is calculated as line width divided by cell size)''
| Polygon shapes are recommended if more than 3 rows of faces must be selected.. 
Caution should be taken when using a "wide" line. The cell size and alignment of the 2d_lfcsh line may result in selecting too many or too few cell faces in the direction of the flow. The FLC input may need to be recalculated to ensure FLC Applied multiplied by the number of cell sides in the direction of flow equates to the intended total form loss.
|-
!rowspan="1" | Polygon
| -
| -
| Total loss per unit length (meters or feet) in the direction of flow
| FLC * cell size applied to all sides of selected cells
|
|}

'''2D Bridge (2d_bg)'''
{| style="text-align: left; margin-left: 0;" class="wikitable" width="80%"
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 7.5%;"| Geometry
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 7.5%;"| Line Type
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 11%;"| Width Attribute
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 22%;"| FLC Input
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 22%;"| FLC Applied
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 30%;"| Notes
|-
!rowspan="3" | Line
| Thin
| zero
| Total form loss of the bridge
| Applies the FLC to a single row of cell sides.
| This approach is cell size independent.
|-
| Thick
| larger than zero
| Total form loss of the bridge
| FLC/2 applied to all sides of the selected cells
| This approach is cell size independent. A cell is selected if the polyline intersects the cell crosshair.
|-
| Wide
| Not supported
| –
| –
| BG polygon shapes are recommended if more than 3 rows of faces must be selected.
|-
!rowspan="1" |Polygon
| -
| ''(used to automatically distribute the total FLC to the selected faces)''
| Total form loss of the bridge
| FLC / Deck_Width * cell size applied to all sides of selected cells
| For bridges modelled using a 2d_bg polygon the relative ratio of the bridge width to the 2D cell size should be 4 or greater. For more information on this see [https://downloads.tuflow.com/Other/2d_bg_R_Bridge_Configuration_Advice_202503.pdf 2d_bg_R_Bridge_Configuration_Advice.pdf].
|}
 
The following diagrams demonstrate how the input FLC is applied for the four geometry options for 2d_lfcsh and 2d_bg layers: 
[[File:2dlfcsh 2dbg combined v2.png|1200px]]

It is good modelling practice to check the [[Check_Files_2d_lfcsh_uvpt | lfcsh_uvpt_check]] and [[Check Files 2d bg uvpt check | bg_uvpt_check]] files to confirm the number of faces selected and the FLC values assigned. It is also strongly recommended to undertake a sensitivity analysis on the applied form losses in the model to check if it makes any difference to the results and/or double check against other methods (hand calculations, other software, CFD modelling), especially if the bridge is near an area of interest. If calibration data is available, this should be used to guide the form loss value specification. 
 

= Common Questions Answered (FAQ)=
== What blockage values should I use for bridge guard rails? ==
The blockage of bridge guard rails can be anything from 100% blocked (solid concrete rails) to 10% blocked (very open rails). In addition, the accumulation of debris during a flood can be substantial as shown in the image below. Sensitivity testing with 100% blockage is recommended.
 
[[File:Bridge rail debris.jpg | 500px]]

== How to conduct sensitivity test for 2D bridges? ==
General recommendations to cross-check the results are:
* Compare computed affluxes against desktop methods (e.g. Hydraulics of Bridge Waterways, 1978) and/or other software including CFD, especially for unusual bridge designs.
* Use any recorded flood marks or general observations from past events to check and calibrate FLC values.
* Conduct sensitivity testing by assessing the impact and influence of FLC values on your modelling objectives. The afflux resulting from the FLC values will be proportional to the velocity head, i.e. ∆h=FLC*(v^2/2g). As such, if velocities are low (e.g. 1 m/s), the results may not be overly sensitive to uncertainties in the FLC values. If completing a check using this equation for a long skew bridge it is best to calculate the total structure velocity from a PO line digitised in the same location as the bridge.

Finally, after completing sensitivity testing and understanding the range of uncertainty due to unknowns like the degree of blockage and influence of FLC values (e.g. +/-20%), you are in a position to discuss with your client how best to proceed. For example, if the modelling is to set planning levels for a development upstream then it may be appropriate to choose values on the higher side (higher FLC values and/or blockage assumptions), noting that the uncertainty may be amply covered by a regulatory freeboard. Conversely, if the development is on the downstream side the conservative approach would be to use the results at the lower end of your FLC/blockage values. 
[[File:Bridge Flood Debris Loading.jpg | 500px]] 

== Should I use both FLC and blockage for layer one in 2D bridge layered flow constriction? ==
When applying FLC and blockage values to model obstructions such as piers, the following considerations need to be taken into account:
* The FLC value applies an energy loss along 1D channels or across 2D cell faces equivalent to FLC*V2/2g where V is the 1D channel velocity or the 2D cell face velocity.
* FLC values are often sourced from publications such as Hydraulics of Bridge Waterways or AustRoads (e.g. Kp chart for piers).
* If possible, establish whether the source of the FLC value is based on the approach velocity (the velocity in the absence of piers) or structure velocity (the velocity with area blocked out by the piers) noting that it often isn’t clear or stated.
** If it is the structure velocity, this is usually the velocity at the vena-contracta (point of greatest contraction within the entrance to the structure and therefore highest velocity) - see image below. Bluff or sharp-edged obstructions will have a much more pronounced vena-contracta, and therefore higher velocity compared with a round-edged obstruction.
** FLC values based on the approach velocity will be higher than those based on the structure velocity to achieve the same energy loss.
* Applying a blockage equivalent to the obstruction width will increase, usually very slightly, the velocity of the 1D channel or 2D cell face. This won’t be the vena-contracta velocity, but a velocity between the approach velocity and the vena-contracta velocity. A greater blockage will need to be applied to emulate the vena-contracta velocity.
* If the FLC source value is based on:
** The approach velocity then there is no need to apply a blockage value.
** The structure velocity then the blockage value should be applied noting that it may be appropriate to apply a larger blockage to take into account the vena-contracta.
* If it is not clear or unknown whether the FLC source value is based on the approach or structure velocity, the recommendation would be to apply the blockage in the interests of being slightly conservative on the upstream flood level calculation.
* For most minor obstructions such as bridge piers, the blockage is usually relatively small and whether included or not has a negligible or minor affect on flood levels compared with other factors such as the approach embankments and the bridge deck.
* Blockage from debris wrapped around piers can have a greater influence on the results than the effect of applying or not applying a blockage. Debris wrapped around piers can be accounted for in the FLC value calculated for the pier layer.
* As always, sensitivity testing with and without blockage and +/- the FLC value is highly recommended to understand their importance in regard to the broader modelling objectives and the effects of uncertainties in the input data, boundaries, other parameters such as Manning’s n values, and the accuracy of the numerical solution scheme (see [https://www.tuflow.com/library/webinars/#maximise_accuracy Maximising the Accuracy of Hydraulic Models webinar]).
[[File: Vena_contracta.png]] 
''Image showing the formation of the vena-contracta.'' 
 

==I don't see results that I expect when using 2d_lfcsh layer==
The 2d_lfcsh layer is a versatile feature that was designed to model bridges in 2D, but can also be used for other applications like fences, buildings raised on pillars and so on.
Some of the unexpected results could be:
* Water level going through the bridge deck in 2D map output.
* Water transiting through 100% blocked Layer 1, e.g. fences with solid base.
* SHMax.csv reporting values above the bridge deck when 2D map output reports water level lower than the top of the bridge deck.

TUFLOW is a 2D solution (not 3D), in the 2d_lfcsh layer the percent blockage and form loss coefficient applied to the cell faces is depth averaged across the entire cell face (across Layer 1, 2 and 3): 
*For bridges, where Layer 2 has a 100% blockage applied, the minimum flow width of 0.001m is used and is averaged with the Layer 1 blockage (based on the depth of the water). This may result in a water level being reported within or above the bridge deck, which would represent the pressure head.
*Layered flow constriction works by adjusting the flow area of the cell faces by any blockages to generate the correct depth averaged velocity at each face at which the form losses are applied as a fraction of the V2/2g kinetic energy. Calculating the correct velocity is critical for determining the losses as the losses are proportional to the velocity squared. 
*For a layered flow constriction cell face the flow area cannot be zero above the invert of Layer 1 to avoid a divide by zero in the computations, therefore a minimum average flow width after applying blockages of 0.001 m is applied. if Layer 1 is 100% blocked, a very small amount of water will flow through Layer 1. If this is unacceptable, instead of applying 100% blockage of Layer 1, the preferred approach is to start the layered flow constriction at the top of Layer 1 or raise the ground elevation to the top of Layer 1 using one of the Z Shape modification functions (e.g. a breakline). 
<ol>
[[File:100% Blockage Diagram.png | 500px]]
</ol>

== Can I model bridge piers explicitly in 2D using very small cells? ==
It isn't recommended to explicitly model bridge piers by blocking out the pier faces in TUFLOW, or in any hydraulic modelling software based on solving Shallow Water Equations(SWE). Due to the 3-dimentiality of the flow and turbulence around a pier, computational fluid dynamics (CFD) approach is often required to simulate the flow around piers explicitly. The wake turbulence behind a simple-shape pier can be resolved to some extent using extremely fine mesh in TUFLOW (see calibration example to a flume experiment in the [https://www.tuflow.com/library/webinars/#structures webinar on Energy Losses at Structures]), however the predictions for head losses show notable sensitivities to the mesh size, the mesh design, and the choice of turbulence model. The extremely fine mesh resolution also results in significantly higher computational costs.

Therefore, the safest and strongly recommended approach with regard to establishing head losses and consequently flood levels, is to model the effects of such obstructions with form loss coefficients (applied to selected mesh cells) that have been derived from physical testing. This approach has been shown to provide the most consistent results across various mesh resolutions. It also has the added benefit that, by avoiding small cells in the mesh, it will provide much more efficient run times for flow solvers.

[[File:Flow round a cylinder.png]]

''The point of flow separation around an object has a major bearing on the drag coefficient and is not reliably reproduced by 2D or 3D software.''


== How to best convert flow constriction data (2d_fc or 2d_fcsh) into newer formats (2d_lfcsh or 2d_bg)? ==
The form loss parameters can be transferred from the flow constriction (2d_fc or 2d_fcsh) to the first layer of the layered flow constriction (2d_lfcsh) or pier layer of the 2d_bg. Definition of the remaining form loss and blockage layer inputs should follow the guidance outlined in [[TUFLOW_2D_Hydraulic_Structures#2D_Layered_Flow_Constriction_.282d_lfcsh.29 | 2D Layered Flow Constriction]] and [[TUFLOW_2D_Hydraulic_Structures#2D_BG_Shape_.282d_bg.29 | 2D BG Shape]] paragraphs. 
When using floating pontoon (type FD in the 2d_fc or 2d_fcsh) different setup might need to be used for different events. For large events when floating pontoon becomes fixed at the top of the supporting piles, standard 2d_lfcsh setup can be used. Smaller events when the pontoon is floating at different heights might require more sensitivity testing of the structure parameters to find out a setup the matches the reality as close as possible. 

== Should I model bridges in 1D or 2D Domain? ==
The recommended approach typically depends on the study objectives and if the channel upstream and downstream of the bridge is modelled in 1D or 2D. To preserve the momentum as accurately as possible the bridge should be modelled in the same dimension as the channel, e.g. 1d_nwk bridge if the channels is in 1D and 2d_bg or 2d_lfcsh if the channel is modelled in 2D. 
In 2D, the expansion/contraction losses are modelled based on the topography and don't need to be estimated as attributes as for 1D modelling. Also, for higher flows where the bridge is overtopped, 2D is preferable approach.

== What is the difference between downstream and upstream controlled flow? ==
Downstream control means a change in downstream water level will cause a change in upstream water level. Upstream control means the upstream water level is insensitive to the downstream water level and usually indicates the occurrence of supercritical flow.

== What FLC values should be used for 2d_bg bridge if hB/T is below 2 or above 6? ==
TMR has extended the CFD simulation to hB/T ratios of 1 to 10. Refer to the [https://docs.tuflow.com/classic-hpc/manual/latest/ TUFLOW Manual] for details.

If hB/T is outside this ratio:
* hB/T ratios of less than 1 represent a very unusual bridge sitting low to the ground, and the peak FLC may increase above the end value (FLC of 0.6) in a way that doesn't follow the research trend or extrapolation. For these cases we would recommend using CFD modelling to obtain a more informed value. Alternatively, computing an FLC based on pressure flow or using 1D culvert might be considered.
* For hB/T ratios of greater than 10, the FLC is likely to continue to decrease, but probably not significantly. Clamping to the end value (FLC of 0.16) might be considered the more conservative approach (if the primary concern is flood levels upstream of the bridge). 
 
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TUFLOW Version Backward Compatibility

2026-04-09T23:57:18Z

Emilie Nielsen: /* Backward Compatibility Change Register */

=Backward Compatibility Change Register=

For a list of new features and changes for each TUFLOW release, refer to the [https://docs.tuflow.com/classic-hpc/changelog/ TUFLOW Classic/HPC Changelog] (for versions since 2023-03-AF). For versions 2023-03-AF and prior, see the relevant release notes in the [https://www.tuflow.com/downloads/tuflow-classichpc-archive/ TUFLOW Downloads Archive].

For backward compatibility and default changes, please see Chapter 18 (Default Changes) of the [https://docs.tuflow.com/classic-hpc/manual/latest TUFLOW Manual].

=Frequently Asked Questions (FAQ)=
== Why are model results developed in an older release different to a newer release? ==
If comparing a Classic model with HPC, also check the [[HPC_FAQ#Will_TUFLOW_HPC_and_TUFLOW_Classic_results_match.3F | Will TUFLOW HPC and TUFLOW Classic results match?]] page in addition to this answer. 
In addition to the above, there are reasons why model results would be different between different TUFLOW releases, whether it is the Classic or HPC solver, as follows:
* General improvements and fine-tuning of the solution scheme, especially for the more complex hydraulic physical terms and situations such as: sub-grid turbulence representation; treatment of shocks (e.g. hydraulic jumps); and transitioning between sub-critical and super-critical flow on steep slopes.
* Some new functionality can cause a significant change in results. For example:
** Sub-Grid Sampling (SGS) applied to an existing model that used a too coarse cell resolution in high flow areas of highly variable topography (relative to the 2D cell size). SGS will greatly improve the model's ability to convey water accurately in these situations with vastly improved results.
** New default sub-grid turbulence scheme in the 2020 release of TUFLOW HPC that is cell size independent and allows modellers to use cell sizes much smaller than the flow depth across all scales from flume to large rivers. For more information on differences between Smagorinsky scheme (HPC releases up to 2020) and the Wu turbulence scheme (2020 onwards) see [[HPC_FAQ#With_Wu_turbulence_scheme_being_the_new_default.2C_are_old_models_using_Smagorinsky_wrong.3F | here]].
* Changes to the default settings and values, e.g.:
**different default eddy viscosity formulation and/or coefficients,
**improved data pre-processing approaches such as sampling materials on cell mid-sides instead of cell centres,
** and many others.
** For backward compatibility the <tt>Defaults</tt> <tt>== </tt> command is available to run old models on new releases to replicate past results (note, sometimes full backward compatibility cannot be catered for due to different code compiler and updates that can't be reverted, especially for several releases earlier).
* New features that use GIS attributes previously reserved (i.e. unused). If these attributes were not populated with the recommended “reserved” value (usually 0 or blank), then they can cause unpredictable results in later releases.
* Bug fixes noting that most bug fixes are input/output related and rarely affect the model's hydraulic calculations.
* Change in timestepping can also produce a small change in results. HPC uses the Runge-Kutta 4th order integrator, which is usually fairly insensitive to time step provided the model is running stably. However when a region is filled by flow that only just overtops an embankment, a 10 mm difference in water levels upstream of the embankment can create a much larger difference in levels downstream. Hence, small differences in time-stepping (along with many other aspects of model setup) can trigger local differences in model results.
* Model orientation (if changed) could also mean slight change in results. This is mostly given by interpolating values from different calculation points. Every cell has nine calculation points. Based on the model origin, all or most of the calculation points would have different topography elevation sampled, which translates to slightly different results.
* If using 1D channel, possibly different cells have been selected as HX boundary and might have different elevations. This can be reviewed in [[Check_Files_1d_to_2d_bc | 1d_to_2d check file]].

Generally, there should not be substantial differences as the fundamental equations being solved are unchanged and TUFLOW Classic and HPC solvers have always solved all the physical terms using a 2nd order spatial approach. The one exception is the turbulence (eddy viscosity) representation, which is the most complex and challenging to solve of all the physical terms (many 2D schemes simply omit this term). If significant differences (>10% of depth change across the whole model) are observed then it’s most likely due to the first four dot points above. To identify in which release(s) the significant changes occurred, the model can be run with the latest build and for past releases. The changes for each release are documented in their release notes. Past releases and release notes are all available [https://www.tuflow.com/downloads/tuflow-classichpc-archive/. here]. Once the exact release where the changes occurred is tracked down, individual features can be turned off to narrow down the cause. 

The recommendation is usually for new or reworked models to use the newest build to take advantage of the latest features and enhancements, some level of calibration might be required for reworked models. The new TUFLOW executable is not different from the previous ones in the meaning that any existing model should be re-calibrated if there are available calibration data. However, particularly if a model is already calibrated, using prior builds of TUFLOW or winding back default settings using <tt>Defaults</tt> <tt>== </tt> command is considered reasonable for established models that are to be used for minor tasks where an update of the model would not be cost effective. 

== How can differences in model results between TUFLOW builds be investigated? ==
Running TUFLOW on a later build from which it was originally calibrated will not necessarily produce the same results, as discussed in [[TUFLOW_Version_Backward_Compatibility#Why_are_model_results_developed_in_an_older_release_different_to_a_newer_release.3F | Why are model results developed in an older release different to a newer release?]].

The following is an example of steps that can be taken when upgrading a TUFLOW model’s executable build, checking for consistency to original results each time.
<ol>
<li> Confirm you are able to run the original model with the original build that would have been used to initially produce results.
* This may be particularly relevant when a model has been externally supplied, for example from a government body.
* Confirm if reproduced results are consistent with supplied results.
<li> Run the original model with the newer build, along with a relevant <tt>Defaults</tt> <tt>== </tt> command (e.g. <tt>Defaults</tt> <tt>== </tt> Pre 2011 when the original build was 2010-10).
* Any differences in results compared to the original results may highlight if there are any changes over time where no backward compatibility had been provided for.
<li> Run the original model with the newer build, and without the <tt>Defaults</tt> <tt>== </tt> command.
* This is more likely to see changes in results compared to the original results, which may require justification to the client or resolution by investigating, isolating and remedying the causes, especially if recalibration is not intended as a subsequent step.
<li> Iteratively run the original model with the newer build, stepping through the different release version options for <tt>Defaults</tt> <tt>== </tt> command.
* This will allow the modeller to investigate and isolate what changes to TUFLOW builds may be affecting results, and when changes appear.
* Then, individually reverting settings that make up a Default group (see Chapter 18 of the [https://docs.tuflow.com/classic-hpc/manual/latest/ TUFLOW Manual]).
* This can help isolate the primary drivers for any differences in results.
* The [https://docs.tuflow.com/classic-hpc/changelog// TUFLOW Classic/HPC Changelog] accompanying build releases are also a key reference.
<li> Develop new improved or updated model version, with the newer build (and any grouped or individual defaults that are deemed necessary to retain from the iterative testing in the prior step).
*Continue to verify results against the original results as you then iteratively add in or update to any newer functionality or formats that may be available in the later build, a good quality assurance check that changes are behaving as expected.
</ol>
 
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}}

TUFLOW Version Backward Compatibility

2026-04-09T23:57:09Z

Emilie Nielsen: /* Backward Compatibility Change Register */

=Backward Compatibility Change Register=

For a list of new features and changes for each TUFLOW release, refer to the [https://docs.tuflow.com/classic-hpc/changelog/ TUFLOW Classic/HPC Changelog] (for versions since 2023-03-AF). For versions 2023-03-AF and prior, see the relevant release notes in the [https://www.tuflow.com/downloads/tuflow-classichpc-archive/ TUFLOW Downloads Archive].

For backward compatibility and default changes, please see Chapter 18 (Default Changes) of the [https://docs.tuflow.com/classic-hpc/manual/latest TUFLOW Manual] 

=Frequently Asked Questions (FAQ)=
== Why are model results developed in an older release different to a newer release? ==
If comparing a Classic model with HPC, also check the [[HPC_FAQ#Will_TUFLOW_HPC_and_TUFLOW_Classic_results_match.3F | Will TUFLOW HPC and TUFLOW Classic results match?]] page in addition to this answer. 
In addition to the above, there are reasons why model results would be different between different TUFLOW releases, whether it is the Classic or HPC solver, as follows:
* General improvements and fine-tuning of the solution scheme, especially for the more complex hydraulic physical terms and situations such as: sub-grid turbulence representation; treatment of shocks (e.g. hydraulic jumps); and transitioning between sub-critical and super-critical flow on steep slopes.
* Some new functionality can cause a significant change in results. For example:
** Sub-Grid Sampling (SGS) applied to an existing model that used a too coarse cell resolution in high flow areas of highly variable topography (relative to the 2D cell size). SGS will greatly improve the model's ability to convey water accurately in these situations with vastly improved results.
** New default sub-grid turbulence scheme in the 2020 release of TUFLOW HPC that is cell size independent and allows modellers to use cell sizes much smaller than the flow depth across all scales from flume to large rivers. For more information on differences between Smagorinsky scheme (HPC releases up to 2020) and the Wu turbulence scheme (2020 onwards) see [[HPC_FAQ#With_Wu_turbulence_scheme_being_the_new_default.2C_are_old_models_using_Smagorinsky_wrong.3F | here]].
* Changes to the default settings and values, e.g.:
**different default eddy viscosity formulation and/or coefficients,
**improved data pre-processing approaches such as sampling materials on cell mid-sides instead of cell centres,
** and many others.
** For backward compatibility the <tt>Defaults</tt> <tt>== </tt> command is available to run old models on new releases to replicate past results (note, sometimes full backward compatibility cannot be catered for due to different code compiler and updates that can't be reverted, especially for several releases earlier).
* New features that use GIS attributes previously reserved (i.e. unused). If these attributes were not populated with the recommended “reserved” value (usually 0 or blank), then they can cause unpredictable results in later releases.
* Bug fixes noting that most bug fixes are input/output related and rarely affect the model's hydraulic calculations.
* Change in timestepping can also produce a small change in results. HPC uses the Runge-Kutta 4th order integrator, which is usually fairly insensitive to time step provided the model is running stably. However when a region is filled by flow that only just overtops an embankment, a 10 mm difference in water levels upstream of the embankment can create a much larger difference in levels downstream. Hence, small differences in time-stepping (along with many other aspects of model setup) can trigger local differences in model results.
* Model orientation (if changed) could also mean slight change in results. This is mostly given by interpolating values from different calculation points. Every cell has nine calculation points. Based on the model origin, all or most of the calculation points would have different topography elevation sampled, which translates to slightly different results.
* If using 1D channel, possibly different cells have been selected as HX boundary and might have different elevations. This can be reviewed in [[Check_Files_1d_to_2d_bc | 1d_to_2d check file]].

Generally, there should not be substantial differences as the fundamental equations being solved are unchanged and TUFLOW Classic and HPC solvers have always solved all the physical terms using a 2nd order spatial approach. The one exception is the turbulence (eddy viscosity) representation, which is the most complex and challenging to solve of all the physical terms (many 2D schemes simply omit this term). If significant differences (>10% of depth change across the whole model) are observed then it’s most likely due to the first four dot points above. To identify in which release(s) the significant changes occurred, the model can be run with the latest build and for past releases. The changes for each release are documented in their release notes. Past releases and release notes are all available [https://www.tuflow.com/downloads/tuflow-classichpc-archive/. here]. Once the exact release where the changes occurred is tracked down, individual features can be turned off to narrow down the cause. 

The recommendation is usually for new or reworked models to use the newest build to take advantage of the latest features and enhancements, some level of calibration might be required for reworked models. The new TUFLOW executable is not different from the previous ones in the meaning that any existing model should be re-calibrated if there are available calibration data. However, particularly if a model is already calibrated, using prior builds of TUFLOW or winding back default settings using <tt>Defaults</tt> <tt>== </tt> command is considered reasonable for established models that are to be used for minor tasks where an update of the model would not be cost effective. 

== How can differences in model results between TUFLOW builds be investigated? ==
Running TUFLOW on a later build from which it was originally calibrated will not necessarily produce the same results, as discussed in [[TUFLOW_Version_Backward_Compatibility#Why_are_model_results_developed_in_an_older_release_different_to_a_newer_release.3F | Why are model results developed in an older release different to a newer release?]].

The following is an example of steps that can be taken when upgrading a TUFLOW model’s executable build, checking for consistency to original results each time.
<ol>
<li> Confirm you are able to run the original model with the original build that would have been used to initially produce results.
* This may be particularly relevant when a model has been externally supplied, for example from a government body.
* Confirm if reproduced results are consistent with supplied results.
<li> Run the original model with the newer build, along with a relevant <tt>Defaults</tt> <tt>== </tt> command (e.g. <tt>Defaults</tt> <tt>== </tt> Pre 2011 when the original build was 2010-10).
* Any differences in results compared to the original results may highlight if there are any changes over time where no backward compatibility had been provided for.
<li> Run the original model with the newer build, and without the <tt>Defaults</tt> <tt>== </tt> command.
* This is more likely to see changes in results compared to the original results, which may require justification to the client or resolution by investigating, isolating and remedying the causes, especially if recalibration is not intended as a subsequent step.
<li> Iteratively run the original model with the newer build, stepping through the different release version options for <tt>Defaults</tt> <tt>== </tt> command.
* This will allow the modeller to investigate and isolate what changes to TUFLOW builds may be affecting results, and when changes appear.
* Then, individually reverting settings that make up a Default group (see Chapter 18 of the [https://docs.tuflow.com/classic-hpc/manual/latest/ TUFLOW Manual]).
* This can help isolate the primary drivers for any differences in results.
* The [https://docs.tuflow.com/classic-hpc/changelog// TUFLOW Classic/HPC Changelog] accompanying build releases are also a key reference.
<li> Develop new improved or updated model version, with the newer build (and any grouped or individual defaults that are deemed necessary to retain from the iterative testing in the prior step).
*Continue to verify results against the original results as you then iteratively add in or update to any newer functionality or formats that may be available in the later build, a good quality assurance check that changes are behaving as expected.
</ol>
 
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}}

TUFLOW Version Backward Compatibility

2026-04-09T23:52:17Z

Emilie Nielsen: /* Backward Compatibility Change Register */

=Backward Compatibility Change Register=

For backward compatibility and release notes, please see Chapter 18 (Default Changes) of the [https://docs.tuflow.com/classic-hpc/manual/latest TUFLOW Manual] 

=Frequently Asked Questions (FAQ)=
== Why are model results developed in an older release different to a newer release? ==
If comparing a Classic model with HPC, also check the [[HPC_FAQ#Will_TUFLOW_HPC_and_TUFLOW_Classic_results_match.3F | Will TUFLOW HPC and TUFLOW Classic results match?]] page in addition to this answer. 
In addition to the above, there are reasons why model results would be different between different TUFLOW releases, whether it is the Classic or HPC solver, as follows:
* General improvements and fine-tuning of the solution scheme, especially for the more complex hydraulic physical terms and situations such as: sub-grid turbulence representation; treatment of shocks (e.g. hydraulic jumps); and transitioning between sub-critical and super-critical flow on steep slopes.
* Some new functionality can cause a significant change in results. For example:
** Sub-Grid Sampling (SGS) applied to an existing model that used a too coarse cell resolution in high flow areas of highly variable topography (relative to the 2D cell size). SGS will greatly improve the model's ability to convey water accurately in these situations with vastly improved results.
** New default sub-grid turbulence scheme in the 2020 release of TUFLOW HPC that is cell size independent and allows modellers to use cell sizes much smaller than the flow depth across all scales from flume to large rivers. For more information on differences between Smagorinsky scheme (HPC releases up to 2020) and the Wu turbulence scheme (2020 onwards) see [[HPC_FAQ#With_Wu_turbulence_scheme_being_the_new_default.2C_are_old_models_using_Smagorinsky_wrong.3F | here]].
* Changes to the default settings and values, e.g.:
**different default eddy viscosity formulation and/or coefficients,
**improved data pre-processing approaches such as sampling materials on cell mid-sides instead of cell centres,
** and many others.
** For backward compatibility the <tt>Defaults</tt> <tt>== </tt> command is available to run old models on new releases to replicate past results (note, sometimes full backward compatibility cannot be catered for due to different code compiler and updates that can't be reverted, especially for several releases earlier).
* New features that use GIS attributes previously reserved (i.e. unused). If these attributes were not populated with the recommended “reserved” value (usually 0 or blank), then they can cause unpredictable results in later releases.
* Bug fixes noting that most bug fixes are input/output related and rarely affect the model's hydraulic calculations.
* Change in timestepping can also produce a small change in results. HPC uses the Runge-Kutta 4th order integrator, which is usually fairly insensitive to time step provided the model is running stably. However when a region is filled by flow that only just overtops an embankment, a 10 mm difference in water levels upstream of the embankment can create a much larger difference in levels downstream. Hence, small differences in time-stepping (along with many other aspects of model setup) can trigger local differences in model results.
* Model orientation (if changed) could also mean slight change in results. This is mostly given by interpolating values from different calculation points. Every cell has nine calculation points. Based on the model origin, all or most of the calculation points would have different topography elevation sampled, which translates to slightly different results.
* If using 1D channel, possibly different cells have been selected as HX boundary and might have different elevations. This can be reviewed in [[Check_Files_1d_to_2d_bc | 1d_to_2d check file]].

Generally, there should not be substantial differences as the fundamental equations being solved are unchanged and TUFLOW Classic and HPC solvers have always solved all the physical terms using a 2nd order spatial approach. The one exception is the turbulence (eddy viscosity) representation, which is the most complex and challenging to solve of all the physical terms (many 2D schemes simply omit this term). If significant differences (>10% of depth change across the whole model) are observed then it’s most likely due to the first four dot points above. To identify in which release(s) the significant changes occurred, the model can be run with the latest build and for past releases. The changes for each release are documented in their release notes. Past releases and release notes are all available [https://www.tuflow.com/downloads/tuflow-classichpc-archive/. here]. Once the exact release where the changes occurred is tracked down, individual features can be turned off to narrow down the cause. 

The recommendation is usually for new or reworked models to use the newest build to take advantage of the latest features and enhancements, some level of calibration might be required for reworked models. The new TUFLOW executable is not different from the previous ones in the meaning that any existing model should be re-calibrated if there are available calibration data. However, particularly if a model is already calibrated, using prior builds of TUFLOW or winding back default settings using <tt>Defaults</tt> <tt>== </tt> command is considered reasonable for established models that are to be used for minor tasks where an update of the model would not be cost effective. 

== How can differences in model results between TUFLOW builds be investigated? ==
Running TUFLOW on a later build from which it was originally calibrated will not necessarily produce the same results, as discussed in [[TUFLOW_Version_Backward_Compatibility#Why_are_model_results_developed_in_an_older_release_different_to_a_newer_release.3F | Why are model results developed in an older release different to a newer release?]].

The following is an example of steps that can be taken when upgrading a TUFLOW model’s executable build, checking for consistency to original results each time.
<ol>
<li> Confirm you are able to run the original model with the original build that would have been used to initially produce results.
* This may be particularly relevant when a model has been externally supplied, for example from a government body.
* Confirm if reproduced results are consistent with supplied results.
<li> Run the original model with the newer build, along with a relevant <tt>Defaults</tt> <tt>== </tt> command (e.g. <tt>Defaults</tt> <tt>== </tt> Pre 2011 when the original build was 2010-10).
* Any differences in results compared to the original results may highlight if there are any changes over time where no backward compatibility had been provided for.
<li> Run the original model with the newer build, and without the <tt>Defaults</tt> <tt>== </tt> command.
* This is more likely to see changes in results compared to the original results, which may require justification to the client or resolution by investigating, isolating and remedying the causes, especially if recalibration is not intended as a subsequent step.
<li> Iteratively run the original model with the newer build, stepping through the different release version options for <tt>Defaults</tt> <tt>== </tt> command.
* This will allow the modeller to investigate and isolate what changes to TUFLOW builds may be affecting results, and when changes appear.
* Then, individually reverting settings that make up a Default group (see Chapter 18 of the [https://docs.tuflow.com/classic-hpc/manual/latest/ TUFLOW Manual]).
* This can help isolate the primary drivers for any differences in results.
* The [https://docs.tuflow.com/classic-hpc/changelog// TUFLOW Classic/HPC Changelog] accompanying build releases are also a key reference.
<li> Develop new improved or updated model version, with the newer build (and any grouped or individual defaults that are deemed necessary to retain from the iterative testing in the prior step).
*Continue to verify results against the original results as you then iteratively add in or update to any newer functionality or formats that may be available in the later build, a good quality assurance check that changes are behaving as expected.
</ol>
 
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}}

HPC Introduction

2026-04-09T23:41:41Z

Emilie Nielsen: /* Introduction */

=Introduction=
Since the 2017-09-AA version, TUFLOW offers HPC (Heavily Parallelised Compute) as an alternate 2D Shallow Water Equation (SWE) solver to TUFLOW Classic. TUFLOW Classic is limited to running a simulation on a single CPU core, whereas HPC provides parallelisation of the TUFLOW model allowing modellers to run a single TUFLOW model across multiple CPU cores or GPU graphics cards (which utilise thousands of smaller CUDA* cores). Simulations using GPU hardware has shown to provide significantly quicker model run times for TUFLOW users. 

In general, most of the functionality and features of TUFLOW Classic are available in HPC. Additionally, HPC offers several advanced features not supported in Classic, including:
* Quadtree and sub-grid sampling
* High resolution map output grids
* Groundwater infiltration and sub-surface flows
* Wu turbulence formulation
* TMR bridge inputs (2d_bg) and simulation methods

===Solution Scheme, Cell Discretisation and Parallelisation===
TUFLOW HPC is an explicit solver for the full 2D Shallow Water Equations (SWE), including a sub-grid scale eddy viscosity model. The scheme is both volume and momentum conserving, is 2nd order in space and 4th order in time, with adaptive or fixed timestepping. It is unconditionally stable. TUFLOW HPC's computational approach differs from TUFLOW Classic, which is a 2nd order (space) implicit finite difference solver. Both TUFLOW HPC and Classic solve the 2D SWE on the same uniform Cartesian grid configuration. Computationally each 2D cell includes 9 sub-grid points. 

[[File: HPC Cell Design.PNG |300px]] 

The ZC point:
* Defines the volume of active water (cell volume is based on a flat square cell that wets and dries at a height of ZC plus the Cell Wet/Dry Depth);
* Controls when a cell becomes wet and dry (note that cell sides can also wet and dry); and
* Determines the bed slope when testing for the upstream controlled flow regime.
The ZU and ZV points:
* Control how water is conveyed from one cell to another;
* Represent where the momentum equation terms are centred and where upstream controlled flow regimes are applied;
* Deactivate if the cell has dried (based on the ZC point) and cannot flow; and
* Wet and dry independently of the cell wetting or drying (see Cell Wet/Dry Depth). This allows for the modelling of “thin” obstructions such as fences and thin embankments relative to the cell size (e.g. a concrete levee).
ZH points:
* Play no role hydraulically. This point location is used for output processing;
* The only elevations written to the .2dm mesh file (by default, binary output is interpolated/extrapolated to the cell corners).

Within the above sub-grid framework, using TUFLOW HPC time derivatives of cell averaged water depth, u-velocity and v-velocity are computed on a cell-by-cell basis and the model evolved using an explicit ODE solver. Calculation of the cell based derivatives are highly independent of each other making it possible to run this solution scheme across multiple processors or GPU cards. Parallelisation is done by breaking up the model into vertical ribbons. Each ribbon of the model is run on a different processor (or GPU card) with boundary information shared between processors at each timestep. 

[[File: Mesh_Ribbon_Splitting.png |360px]] 

===Mass Conservation and Timestep===

The explicit finite volume solution scheme utilised in HPC is mass conserving by construction (0% mass error). This differs to TUFLOW Classic, which can continue to simulate a model with some volume error due to it being an implicit finite difference scheme. The stability of the explicit finite volume scheme used in TUFLOW HPC is linked to the timestep, flow velocities, water depth, and eddy viscosity. The maximum timestep that can be used while maintaining model stability changes as the model evolves. While it is possible to choose a fixed timestep ahead of time (similarly to TUFLOW Classic), shorter run times and guaranteed model stability from start to finish may be achieved through the use of adaptive timestepping where the solver continually modifies the timestep based on various stability criteria. This is explained in more detail in our [[HPC_Adaptive_Timestepping | Adaptive Timestepping]] page. 

===Compatible Graphic Cards (GPU) ===
TUFLOW HPC’s GPU hardware module is only compatible with NVIDIA architecture CUDA enabled GPU cards. AMD GPU cards are NOT compatible. A list of CUDA enabled GPUs can be found on the following website: http://developer.nvidia.com/cuda-gpus .
To check if your computer has an NVIDA GPU and if it is CUDA enabled:
* Right click on the Windows desktop;
* If you see “NVIDIA Control Panel” or “NVIDIA Display” in the pop up dialogue, the computer has an NVIDIA GPU;
* Click on “NVIDIA Control Panel” or “NVIDIA Display” in the pop up dialogue;
* The GPU model should be displayed in the graphics card information;
* Check to see if the graphics card is listed on the following website: http://developer.nvidia.com/cuda-gpus
On the NVIDA website each CUDA enabled graphics card has a “Compute Capability” listed. For cards with a compute capability of 1.2 or less, only the single precision version of the GPU Module can be utilised. However, benchmarking has indicated that the double precision version is NOT required and that the TUFLOW_iSP exe should be used for all TUFLOW HPC GPU simulations. Extensive GPU hardware benchmarking has been undertaken to assist users who are upgrading hardware for TUFLOW modelling. Over 50 different hardware options have been tested for their speed performance. The results are provided on the [[Hardware_Benchmarking | Hardware Benchmarking]] page.

===Benefits of HPC===
So what does this mean for modellers? 
By providing the ability to run models on Graphics Cards, we can achieve significantly shorter model run times, increasing our modelling capabilities to be able to run continuous hydraulic models, with higher cell resolution, across larger extents and more scenarios. Common TUFLOW HPC applications include:
* Monte Carlo design assessments
* Rainfall ensemble design assessments
* High resolution 1D underground / 2D above ground integrated urban drainage
* High resolution floodplain lumped hydrology / hydraulic modelling (either fully 2D or including nested 1D open channels and pipes)
* Whole of catchment direct rainfall
* Flood forecast modelling
* Long-term water resource management modelling

The unconditional stability and higher order accuracy of TUFLOW HPC also lends itself well to highly transient situations, such as dam break assessments, where other solvers would either become unstable, lose accuracy or experience impractical simulation slow-down due to the need to solve at an extremely small timestep. 
 
{{Tips Navigation
|uplink=[[ HPC_Modelling_Guidance | Back to HPC Modelling Guidance]]
}}

TUFLOW Viewer

2026-04-09T23:18:21Z

Emilie Nielsen:

TUFLOW Viewer replaces Crayfish and TUPLOT as the TUFLOW result viewer for [[QGIS_Tips | QGIS]] (version 3.6 onwards). It uses the Mesh Data Abstraction Library (MDAL) available in QGIS to display and interact with TUFLOW map output results, and the TUFLOW results python library (the same library used by TUPLOT in earlier versions of QGIS) for viewing TUFLOW time series results. 

The TUFLOW Viewer tool has been significantly updated in the 2026.0.0 QGIS TUFLOW Plugin release. Refer to the [https://docs.tuflow.com/qgis-tuflow-plugin/latest/tuflow-viewer/ TUFLOW Viewer Documentation] for more information. 
 
__TOC__

=Getting Started=
==QGIS Version==
''A few notes on the recommended QGIS version:'' 

It is recommended to use the latest version of QGIS. The reasons for this are:
* TUFLOW Viewer is developed using the latest version, and although backwards compatibility is maintained as best as possible, TUFLOW Viewer is tested more frequently on the latest QGIS version.
* The mesh data provider (MDAL) and the temporal controller (which now underpins the mesh datasets in QGIS) are both relatively new in comparison to other libraries (e.g. GDAL) and are therefore more regularly updated with new features, enhancements, and bug fixes by the QGIS developers. TUFLOW Viewer takes advantage of these updates. 

Although TUFLOW Viewer has been developed to be consistent across QGIS versions, it is not always possible. Some QGIS developments and behaviour changes have led to TUFLOW Viewer behaviour also changing either through necessity or to keep in-line with the QGIS development direction. The below is a current list of known behaviour changes due to QGIS version: 
<ol>
<li> '''Date-time format within TUFLOW Viewer''' - QGIS 3.14 introduced the '''temporal controller''' 
* Prior to QGIS 3.14, TUFLOW Viewer stored all results internally as relative time. The user could display as date-time and the reference time by changing '''Zero Date''' in '''Settings >> Options'''.
* QGIS 3.14, TUFLOW Viewer tried to mimic the behaviour of previous versions but the reference time could also be altered natively in the mesh layer '''Properties'''. Note on this version, this is the first QGIS release with the '''temporal controller''' and as a consequence some of the functionality matured and changed in subsequent versions. Users may experience strange behaviour when using TUFLOW Viewer with the QGIS 3.14 if using date-time format. It is recommended to upgrade to later versions of QGIS if date-time format is required.
* Post QGIS 3.14 TUFLOW Viewer stores all results internally as absolute time and the user must change the reference time in the native properties of the mesh layer to alter the dates being displayed. '''Zero Date''' now only changes how the relative time is displayed in TUFLOW Viewer and doesn't change the mesh layer reference time.
* Please follow the link below on how to use isodate (date-time) format in TUFLOW Viewer in QGIS 3.16+ (recommended minimum version if using date-time format): [[TUFLOW_Viewer_-_Isodate_(Date-Time)_Format | Working With Isodate (Date-Time) format]].
</ol>

'''Other Known Issues''' 
* QGIS 3.24 uses Matplotlib v3.5.1 which contains the following known bug which may affect users when re-labelling datasets within the TUFLOW Viewer plot window: 
: [[TUFLOW_Viewer_Matplotlib_v3.5.1_Bug | TUFLOW Viewer - Matplotlib v3.5.1 bug]] 
* "ValueError: Failed to find font DejaVu Sans:style=normal:variant=normal:weight=normal:stretch=normal:size=10.0, and fallback to the default font was disabled"
: [[TUFLOW_Viewer_Matplotlib_Font_Error | TUFLOW Viewer - Matplotlib Font Error]] 

==Installation or Version Upgrade==
===Installation===
TUFLOW Viewer is a free tool that comes as part of the TUFLOW plugin in QGIS. For instructions on how to install the plugin, please follow these steps: [[TUFLOW_QGIS_Plugin#Installation_of_Plugin |Installation of Plugin]]. 
There are also instructions on installing plugins in the QGIS documentation - if you choose to follow the QGIS documentation, the plugin is called "TUFLOW" in the repository: [https://docs.qgis.org/3.16/en/docs/training_manual/qgis_plugins/fetching_plugins.html Link to QGIS Documentation - Installing and Managing Plugins]. 

===Plugin Upgrades===
It's recommended to upgrade the plugin whenever a new version is released. The upgrade process is typically done via the Plugin Manager ('''QGIS Drop Menu: Plugins >> Manage and Install Plugins'''). 
 
[[File: TUFLOW_Plugin_Update_01.png]] 
If you encounter an error while upgrading the plugin please follow these steps: [[ TUFLOW_QGIS_Plugin#Error_While_Upgrading_Plugin | Error While Upgrading Plugin ]].

==Development Version==
It's possible to test out the latest development version of the plugin and TUFLOW Viewer by following the instructions here: [[Installing_the_Latest_Development_Version_of_the_TUFLOW_Plugin | Installing the Latest Development Version of the TUFLOW Plugin]].

=Using TUFLOW Viewer=
==Opening the TUFLOW Viewer==
After installing the QGIS TUFLOW plugin, the TUFLOW Viewer tool can be opened by clicking the following icon in the plugin toolbar: 
 
[[File: TUFLOW_Plugin_Toolbar_TUFLOW_Viewer_01.png]] 

==Loading Results==
TUFLOW simulation results can be loaded two ways: 
<ol>
<li> Select '''File >> Load Results''' from the TUFLOW Viewer drop down menu. 
 
[[File:TUFLOW_Viewer_Load_Results_01a.png]] 
 
<li> Right Click in the '''Open Results''' panel and select '''Load Results'''. 
 
[[File: TUFLOW_Viewer_Load_Results_02a.png]] 
 
</ol>
Using either of the above methods, the following result load options are available:
<ol>
<li> '''[[TUFLOW_Viewer_-_Load_Results | Load All Results]]''' --> This is done via a TCF or TLF file and will load in all results (Map Outputs and ESTRY Time Series). ''Note: the Load All Results feature is not yet enabled for TUFLOW FV FVC files.''
<li> '''[[TUFLOW_Viewer_-_Load_Results_-_Map_Outputs | Load Results - Map Outputs]]''' --> Select map output mesh results file ('''*.xmdf, *.dat, *.2dm, *.xmdf.sup, *.dat.sup, *.nc''' ''(supports netCDF format from TUFLOW FV output only)'').
<li> '''[[TUFLOW_Viewer_-_Load_Results_-_Time_Series | Load Results - Time Series]]''' --> Select ESTRY / SWMM time series output results ('''*.tpc *.gpkg''').
<li> '''[[TUFLOW_Viewer_-_Load_Results_-_Time_Series_FM | Load Results - Flood Modeller Time Series]]''' --> Load Flood Modeller results. This requires a '''*.gxy''' and result '''*.csv''' file to be exported from Flood Modeller.
<li> '''[[TUFLOW_Viewer_-_Load_Results_-_Particles | Load Results - Particle Tracking Module]]''' --> Select output from particle module ('''*.nc''') which will typically be suffixed with '''_ptm'''.
<li> '''[[TUFLOW_Viewer_-_Load_Results_-_NetCDF_Grid | Load Results - NetCDF Grid]]''' --> Load TUFLOW NC or HRNC map output results.
<li> '''[[TUFLOW_Viewer_-_Import_1D_Hydraulic_Tables | Import 1D Hydraulic Tables]]''' --> Select a '''_1d_ta_tables_check.csv''' check file.
<li> '''[[TUFLOW_Viewer_-_Import_2D_BC_Tables | Import 2D BC Tables]]''' --> Select a '''_2d_bc_tables_check.csv''' check file.
<li> '''[[TUFLOW_Viewer_-_Import_1D_ESTRY_Cross_-_Sections | Import 1D ESTRY Cross-Sections]]''' --> This will automatically happen if an appropriate TUFLOW input is opened in QGIS while TUFLOW Viewer is open (e.g. 1d_xs).
<li> '''[[TUFLOW_Viewer_-_Importing_a_User_Defined_Time_Series_To_Display_On_The_Plot | Importing a User Defined Time Series Dataset To Display In The Plot Window]]'''
<li> '''[[TUFLOW_Viewer_-_Import_FV_Tide_BC_NetCDF | Import FV Tide BC NetCDF]]'''
<li> '''[[TUFLOW_Viewer_-_Loading_Results_While_TUFLOW_is_Running | Loading Results While TUFLOW is Running]]'''
</ol>

===Troubleshooting===
If you receive an error similar to that shown below when attempting to load results from a TCF you will need to fix the encoding of your TUFLOW control files: 
<pre>
UnicodeDecodeError: 'utf-8' codec can't decode byte 0x92 in position 626: invalid start byte
</pre>
This error is caused by incompatible encoding of the TUFLOW control files. You can resolve this issue by changing the encoding of all your TUFLOW control files to a single type (typically UTF-8). You can do this using Notepad++. Please see the following link for instructions on how to do this (refer last image): [[TUFLOW_Message_0060 | TUFLOW Message 0060]]. 

== TUFLOW-SWMM Results ==
Results from a linked TUFLOW-SWMM model can be loaded via the standard menu options (available from the TUFLOW plugin version 3.10):
* '''[[TUFLOW_Viewer_-_Load_Results_-_Time_Series | Load Results - Time Series]]''' To load the GPKG time series format (_swmm_ts.gpkg) by itself. The GPKG time series format is a new format similar to the .tpc with some additional functionality. More information can be found in the [[#GPKG_Time_Series_Format | GPKG Time Series Format]] section.
* '''[[TUFLOW_Viewer_-_Load_Results_-_Map_Outputs | Load Results - Map Outputs]]''' To load in 2D map output results
* '''[[TUFLOW_Viewer_-_Load_Results | Load Results]]''' To load all available results from the model. This includes .xmdf, .tpc, and .gpkg results which could all be available for a given model run. Note that .tpc and .gpkg are both time series type results and will load separate GIS _PLOT_ layers.

== GPKG Time Series Format ==
The GPKG time series format is a new format similar to the .tpc with enhanced temporal functionality. Currently the GPKG time series format is only supported as an output from SWMM in TUFLOW-SWMM linked models and only supported in TUFLOW Plugin version 3.10+ and QGIS 3.16+. 
 
The GPKG format is different from the TPC format as it supports temporal styling in QGIS. As an example, the line width of the channels can be varied by both time and flow, with wider lines showing higher flow than thinner lines at a particular timestep. The format is fully compatible with the QGIS temporal controller and reacts dynamically as the temporal controller is updated. This results in a dynamic, and intuitive, method of showing the user the flood progression in the 1D system. Another benefit of being compatible with the core QGIS temporal capabilities is that the styling will also be dynamically updated if included in an animation export. TUFLOW Viewer's animation export tool has been updated to enable GPKG results to be exported with 2D results or even by itself. 
 
The layer's styling can be automatically set using the TUFLOW Plugin via the layer's right-click context menu (under the TUFLOW submenu) or will automatically by styled if the results are loaded via TUFLOW Viewer. Examples of this format in QGIS are linked below:
* [[Automatically_Styling_GPKG_Time_Series | Styling layers from the GPKG time series output]]
* [[TUFLOW_Viewer_-_Load_Results_-_GPKG_Time_Series | Loading results via TUFLOW Viewer]]
The GPKG time series format is an open format and the specification is detailed at the below link:
* [[GPKG_Time_Series_Format_Specification | GPKG Time Series Format Specification]]

== Data Selection, Display and Styling==
===Map Output===
Map Outputs are the time varying 2D result outputs from TUFLOW (or 3D outputs from TUFLOW FV). Data selection, display, styling and plotting instructions for Map Output results in TUFLOW Viewer are described below:
<ol>
<li> Load Map Output results either via:
<ol>
<li> '''[[TUFLOW_Viewer_-_Load_Results | Load All Results]]''', or
<li> '''[[TUFLOW_Viewer_-_Load_Results_-_Map_Outputs | Load Results - Map Outputs]]'''
</ol>
<li> '''[[TUFLOW_Viewer_-_Reload_Results | Reload Results]]''' --> Reload and update results
<li> '''[[TUFLOW_Viewer_-_Map_Outputs_-_Change_Result_Selection | Change Simulation Result Selection]]''' --> Changing between different simulation results is done by selecting the result name(s) in the 'Open Results' widget.
<li> '''[[TUFLOW_Viewer_-_Map_Outputs_-_Changing_Result_Type | Change Result Type Selection]]''' --> Changing between different result types is done using the 'Result Type' widget.
<li> '''[[TUFLOW_Viewer_-_Map_Outputs_-_Displaying_Maximum | Display Result Maximum]]''' --> If available, maximums can be toggled on/off for the different result types.
<li> '''[[TUFLOW_Viewer_-_Map_Outputs_-_Displaying_Vectors | Display Vectors]]''' --> Vector results can be displayed in combination with any of the scalar result types (e.g. velocity vectors can be displayed with depth).
<li> '''[[TUFLOW_Viewer_-_Map_Outputs_-_Styling_Scalar_Types | Style Scalar Map Outputs]]''' --> Styling scalar map output results is similar to styling raster layers in QGIS.
<li> '''[[TUFLOW_Viewer_-_Map_Outputs_-_Styling_Vector_Types | Style Vector Map Outputs]]''' --> Similar to the styling the scalar map outputs, there are a range of options for styling the vector layers.
<li> '''[[TUFLOW_Viewer_-_Map_Outputs_-_Saving_Default_Styles | Save Default Styles]]''' --> Users can save default styles for result types so they are automatically applied each time results are imported using TUFLOW Viewer.
<li> '''[[TUFLOW_Viewer_-_Map_Outputs_-_Displaying_The_Mesh | Display The Mesh]]''' --> The quickest way to toggle the mesh is to click the grid box in TUFLOW Viewer.
<li> '''[[TUFLOW_Viewer_-_Map_Outputs_-_3D_to_2D_Depth_Averaging_Method | 3D to 2D Depth Averaging]]''' --> For 3D map output results, the 3D to 2D depth averaging method can be changed in the layer properties.
<li> '''[[TUFLOW_Viewer_-_Toggling_Between_Output_Timesteps | Lock/Unlock Output Time Steps from Different Result Datasets]]''' --> Locking Plot Output Timesteps to the Map Output Interval.
<li> '''[[TUFLOW_Viewer_-_Isodate_(Date-Time)_Format | Working With Isodate (Date-Time) Format]]''' --> View results using absolute time format (dd/mm/yyyy hh:mm:ss) instead of relative time format (hh:mm:ss).
<li> '''[[TUFLOW_Viewer_-_Map_Outputs_-_Plotting_Time_Series | Map Output Plot - Plotting Time Series]]''' --> Plotting Map Output results.
<li> '''[[TUFLOW_Viewer_-_Map_Outputs_-_Plotting_Cross-Sections_And_Longitudinal_Profiles | Map Output Plot - Plotting Cross-Sections and Longitudinal Profiles]]''' --> Plotting Map Output results.
<li> '''[[TUFLOW_Viewer_-_Map_Outputs_-_Plotting_Flow | Map Output Plot - Plotting Flow]]''' --> Plotting Map Output results.
<li> '''[[TUFLOW_Viewer_-_Map_Outputs_-_Curtain_Plot | Map Output Plot - 3D Curtain Plot]]''' --> Plotting Map Output results.
<li> '''[[TUFLOW_Viewer_-_Map_Outputs_-_Vertical_Profile | Map Output Plot - 3D Vertical Profile]]''' --> Plotting Map Output results --> Plotting Map Output results.
<li> '''[[TUFLOW_Viewer_-_Map_Outputs_-_3D_to_2D_Depth_Averaged_Time_Series | Map Output Plot - Plotting 3D to 2D Depth Averaged Time Series]]''' --> Plotting Map Output results.
<li> '''[[TUFLOW_Viewer_-_Map_Outputs_-_3D_to_2D_Depth_Averaged_Cross-Sections | Map Output Plot - Plotting 3D to 2D Depth Averaged Cross-Sections]]''' --> Plotting Map Output results.
<li> '''[[TUFLOW_Viewer_-_Map_Outputs_-_Plotting_From_Vector_Layer | Map Output Plot - Plotting From Vector a Layer (e.g. shp file)]]''' --> Plotting Map Output results.

</ol>
 
[[file: MapOutputs HeaderImg.PNG|650px]] 
 

===Time Series Output===
Time series outputs are typically 1D result outputs or 2D time series results (plot outputs or reporting locations). Time series results consist of two elements, the result datasets and GIS layers that the user can interact with to customise the plot selection in TUFLOW Viewer.
<ol>
<li> Load time series output results either via:
<ol>
<li> '''[[TUFLOW_Viewer_-_Load_Results | Load All Results]]''', or
<li> '''[[TUFLOW_Viewer_-_Load_Results_-_Time_Series | Load Results - Time Series]]''' for TUFLOW models, or:
<li> '''[[TUFLOW_Viewer_-_Load_Results_-_Time_Series_FM | Load Results - Time Series Flood Modeller]]''' for TUFLOW linked Flood Modeller 1D models.
</ol>
<li> '''[[TUFLOW_Viewer_-_Time_Series_Outputs_GIS_Data | Time Series Output - GIS Data]]'''
<li> '''[[TUFLOW_Viewer_-_Time_Series_Outputs_-_Plotting_Time_Series | Time Series Output - Plotting Time Series]]'''
<li> '''[[TUFLOW_Viewer_-_Time_Series_Outputs_-_Plotting_Longitudinal_Profiles | Time Series Output - Plotting Longitudinal Profiles]]'''
<li> '''[[TUFLOW_Viewer_-_Showing_Selected_Elements_And_Selecting_Sub-Sets | Identifying Selected Elements and Selecting Sub-Sets]]'''
<li> '''[[TUFLOW_Viewer_-_Time_Series_Outputs_-_Plotting_1D_Cross-Section_Inputs | Plotting 1D Cross-Section Inputs (with / without results)]]'''
<li> '''[[TUFLOW_Viewer_-_Time_Series_Outputs_-_Plotting_1D_Hydraulic_Table_Check_Files | Plotting 1D Hydraulic Table Check Files]]'''
<li> '''[[TUFLOW_Viewer_-_Extracting_Median_And_Mean_Time_Series | Extracting Median and Mean Time Series - Australian Rainfall and Runoff]]'''
<li> '''[[TUFLOW_Viewer_-_Plotting_1D_Flow_Regime | Plotting 1D Flow Regime]]'''
<li> '''[[TUFLOW_Viewer_-_Import_2D_BC_Tables | Plotting 2D Boundary Condition Tables]]'''
<li> '''[[TUFLOW_Viewer_-_Toggling_Between_Output_Timesteps | Lock/Unlock Output Time Steps from Different Result Datasets]]'''
<li> '''[[TUFLOW_Viewer_-_Isodate_(Date-Time)_Format | Working With Isodate (Date-Time) Format]]'''
</ol> 
[[File: TimeSeries_HeaderImg.PNG|650px]] 
 

===Particle Tracking Output===
<ol>
<li> '''[[TUFLOW_Viewer_-_Particle_Outputs | Particle Tracking Outputs]]'''
<li>'''[[TUFLOW_Viewer_-_Isodate_(Date-Time)_Format | Working With Isodate (Date-Time) Format]]'''
<li> '''[[TUFLOW_Viewer_-_Toggling_Between_Output_Timesteps | Lock/Unlock Output Time Steps from Different Result Datasets]]'''
</ol>
[[File: Particles HeaderImg.PNG|650px]] 

==General Plot Display Options==
<ol>
<li> '''[[TUFLOW_Viewer_-_Summary_of_Plotting_Toolbar | Summary of Plotting Toolbar Options]]''' 
<li> '''[[TUFLOW_Viewer_-_Using_A_Secondary_Axis | Using a Secondary Axis]]'''
<li> '''[[TUFLOW_Viewer_-_Using_A_Date_Axis | Using a Date Axis]]'''
<li> '''[[TUFLOW_Viewer_-_Showing_The_Current_Time | Displaying the Current Time]]'''
<li> '''[[TUFLOW_Viewer_-_Customising_The_Plot_Legend | Customising The Legend]]'''
<li> '''[[TUFLOW_Viewer_-_Customising_The_Plotting_Styles | Customising The Plotting Styles]]'''
<li> '''[[TUFLOW_Viewer_-_Customising_The_Plot_Axes | Customising The Plot Axes]]'''
<li> '''[[TUFLOW_Viewer_-_Toggling_Plot_Grid_Lines | Plot Grid Line Display]]'''
<li> '''[[TUFLOW_Viewer_-_Importing_a_Custom_Colour_Ramp_For_The_Curtain_Plot | Importing a Custom Colour Ramp For The Curtain Plot]]'''
<li> '''[[TUFLOW_Viewer_-_Navigating_And_Querying_The_Plot | Navigating And Querying The Plot]]'''
<li> '''[[TUFLOW_Viewer_-_Auto_Update_Plot_From_Cursor_Location | Auto Update Plot From Cursor Location]]'''
<li> '''[[TUFLOW_Viewer_-_Viewing_The_Vertical_Mesh | 3D Mesh Vertical Layer Display]]'''
<li> '''[[TUFLOW_Viewer_-_Hiding_The_Plotting_Window | Hiding the Plot Window]]'''
<li> '''[[TUFLOW_Viewer_-_Customising_The_Plot_Background_Colour | Customising the Plot Background Colour]]'''
<li> '''[[TUFLOW_Viewer_-_Setting_The_Plot_Default_Font_Size | Setting the Default Font Size For the Plot]]'''
<li> '''[[TUFLOW_Viewer_-_Toggling_Between_Output_Timesteps | Lock/Unlock Output Time Steps from Different Result Datasets]]'''
<li> '''[[TUFLOW_Viewer_-_Changing_Icon_Size | Changing the Icon Size]]'''
<li> '''[[TUFLOW_Viewer_-_Summary_Of_Options | Settings Options]]'''
</ol>

[[File: Plotting_HeaderImg.PNG | 650px ]] 
 

==Exporting Animations, Data, Plots and Maps ==
TUFLOW Viewer offers the ability to export animations, data interegation points/lines, maps and plots: 
<ol>
<li> '''[[TUFLOW_Viewer_-_Exporting_An_Animation | Exporting An Animation]]''' 
: [[File: Animation_cover.gif]] 
<li> '''[[TUFLOW_Viewer_-_Exporting_And_Copying_A_Plot | Exporting and Copying a Plot]]'''
<li> '''[[TUFLOW_Viewer_-_Exporting_The_Drawn_GIS_Plot_Features | Exporting The Drawn GIS Plot Points / Lines]]'''
<li> '''[[TUFLOW_Viewer_-_Batch_Exporting_Maps | Batch Exporting Maps]]'''
<li> '''[[TUFLOW_Viewer_-_Batch_Exporting_Plots | Batch Exporting Plots]]'''
</ol>
: [[File: Maps_Cover_Image.PNG | 550px]] 

= Python Error Troubleshooting =
Occasionally the TUFLOW plugin will throw an exception and this will produce a '''Python Error''' which is displayed either as a yellow banner at the top of the map window or a window may appear stating than an 'Error has occurred while executing Python code'. 
[[File: PythonError.PNG]] 
When this occurs it means that the TUFLOW plugin has encountered something unusual or a situation that it does not know how to handle (i.e. it has reached a line in the code that has failed to execute and as a consequence Python has bailed out). This means all the code below this point that was meant to execute has not. This can have knock-on consequences as variables may not exist or be set to incorrect values and signal handling (e.g. what happens when a menu item is clicked) may be broken. As such, a python error can lead to further python errors that would normally not have occurred. Because of this flow-on effect the first python error is usually the most important. 

If you encounter a python error please:
<ol>
<li> Email the '''Stack Trace''' to [mailto:support@tuflow.com support@tuflow.com] with a description of the steps that produced the python error (as best you can describe it). This is to help us identify bugs and fix the plugin so that it catches this exception in the future.
<li> If you find that you are now experiencing further python errors (probably caused by the initial error) you can try the following alternative in order of severity (least to worst):
<ol>
<li> On the TUFLOW Viewer menu bar '''File >> Reload TUFLOW Viewer''' - this will reload TUFLOW Viewer, resetting all variables and signals. You will be required to load in any time series results again and other settings may also be reset. Map output results will remain in the workspace and be reloaded into TUFLOW Viewer.
<li> Save the QGIS workspace (.qgz) and restart QGIS.
<li> Restart QGIS - you can save the workspace (.qgz), however you should first select on the TUFLOW Viewer menu bar '''File >> Close TUFLOW Viewer Completely''' - this will close the Viewer and also remove all settings associated with it from the workspace so that the problematic variable is not accidentally reloaded with the workspace.
<li> The last resort option is to restart QGIS and load and create a new workspace from scratch (do not load a saved workspace).
</ol>
</ol>
 
{{Tips Navigation
|uplink=[[TUFLOW_QGIS_Plugin#Usage| Back to TUFLOW QGIS Plugin Main Page]]
}}
 
 
 
{{Tips Navigation
|uplink=[[Main_Page| Back to Wiki Main Page]]
}}

TUFLOW QGIS Plugin

2026-04-09T23:14:28Z

Emilie Nielsen: /* Introduction */

=Introduction=
If you are using QGIS as your model development or result viewing environment we strongly recommend installing the TUFLOW QGIS Plugin. It includes numerous tools to increase workflow efficiency. It also includes powerful result viewing functionality via its [[TUFLOW_Viewer | TUFLOW Viewer]]. This page describes the process of installing and using the Plugin.
 
See the [https://docs.tuflow.com/qgis-tuflow-plugin/changelog/ TUFLOW QGIS Plugin Changelog] for changes between versions of the plugin (since version 3.2).

=Installation of Plugin=
To enable the plugin please follow the instructions below:
<ol>
<li>Download the plugin from the QGIS official repository, '''Plugins >> Manage and Install Plugins'''</li>
[[File:QGIS_TUFLOW_000.PNG|400px]]
<li>In the manager, search for "TUFLOW".</li>
<li>Select TUFLOW, and "Install Plugin".</li>
[[File:QGIS_TUFLOW_001.PNG|400px]]
<li>Once enabled the plugin should be accessible from the '''Plugins >> TUFLOW''' menu item:</li>
[[File:QGIS_TUFLOW_003.PNG|400px]]
<li>Before using, check that the prerequisite python modules are also installed (see below).
</ol> 

=Development Version=
It's possible to test out the latest development version of the plugin and TUFLOW Viewer by following the instructions below: 
[[Installing_the_Latest_Development_Version_of_the_TUFLOW_Plugin | Installing the Latest Development Version of the TUFLOW Plugin]]
 

= Prerequisites=
The TUFLOW plugin uses the following python modules which '''may''' need to be separately installed. These may have been installed with other software, to check if they are installed on your machine:
<ol>
<li> Install the TUFLOW plugin (see instructions above)</li>
<li> Open the TUFLOW plugin '''Plugins >> TUFLOW''' </li>
<li> Check that the required dependencies are installed from the menu. '''TUFLOW >> About >> Check Python Dependencies Installed'''. </li>
[[File:QGIS_TUFLOW_004.PNG|600px]]
</ol>

All going well you will get a notification to tell you that the required modules are installed. If not, you will be notified if you need to install either of the python modules below: 
Please ensure QGIS / python is installed before installing the below. 
* numpy (see https://sourceforge.net/projects/numpy/files/NumPy/1.6.1/numpy-1.6.1-win32-superpack-python2.7.exe/download)
* matplotlib (see https://sourceforge.net/projects/matplotlib/files/matplotlib/matplotlib-1.1.0/matplotlib-1.1.0.win32-py2.7.exe/download)
 

=Usage=
Each function in the utility has a separate page documenting the usage.

The first step for a project is to create the project / save the settings with the [[QGIS_TUFLOW_Create_Project | Create or Configure TUFLOW Project]] tool. Subsequent tools rely on the information stored at this stage to work best.

=== Editing Tools ===
<ol>
<li> [[QGIS_TUFLOW_Create_Project | Create or Configure TUFLOW Project]]</li>
<li> [[QGIS_TUFLOW_Import_Empty | Import Empty (template GIS file)]]</li>
<li> [[QGIS_TUFLOW_Insert_TUFLOW_Attributes_to_Existing_Layer | Insert TUFLOW Attributes to Existing Layer]]</li>
<li> [[QGIS_TUFLOW_Increment_Layer | Increment Selected Layer]]</li>
<li> [[QGIS_TUFLOW_Reload_Data | Reload Data]]
<li> [[QGIS_TUFLOW_Arch_Bridge_Editor | Arch Bridge Editor]]
<li> [[QGIS_TUFLOW_Copy_TUFLOW_Command | Copy TUFLOW Command]]
</ol>
=== Run Tools ===
<ol>
<li> [[QGIS_TUFLOW_Run_TUFLOW | Run TUFLOW simulation]]</li>
<li> [[TUFLOW_Runner | TUFLOW Runner]]</li>
<li> [[QGIS_TUFLOW_Run_TUFLOW_Utilities | Running TUFLOW Utilities]]</li>
</ol>

=== Visualisation Tools ===
<ol>
<li> [[TUFLOW_Viewer | TUFLOW Viewer ]](result visualisation toolkit)
<li> [[QGIS_TUFLOW_Styles | Applying TUFLOW styles]]
<li> [[QGIS_TUFLOW_Import_Check_Files_From_Folder | Import Check Files From Folder]]
<li> [[QGIS_TUFLOW_Load_Layers_From_TCF | Load TUFLOW Layers From TCF]]
<li> [[QGIS_TUFLOW_Filter_and_Sort_TUFLOW_Layers | Filter and Sort TUFLOW Layers]]
<li> [[QGIS_TUFLOW_Apply_GPKG_Layer_Names | Apply GPKG Layer Names]]
<li> [[QGIS_TUFLOW_Apply_Label_to_Current_Layer | Apply Label to Current Layer]]
<li> [[QGIS_TUFLOW_Apply_Stability_Styling | Apply Stability Styling]]
</ol>
=== Hydrology Tools ===
<ol>
<li> [[QGIS_ARR_to_TUFLOW | ARR to TUFLOW]]
<li> [[QGIS_ReFH2_to_TUFLOW | ReFH2 to TUFLOW]]
<li> [[QGIS_SCS_to_TUFLOW | SCS to TUFLOW]]
</ol>
=== Integrity Tools ===
<ol>
<li> [[1D_Integrity_Tool | 1D Integrity Tool]]
</ol>
=== SWAN GIS Tools ===
For more information on SWAN GIS Tools please visit the following TUFLOW FV Wiki page: '''[https://fvwiki.tuflow.com/index.php?title=SWAN_GIS_Tools SWAN GIS Tools]'''. Links to the individual tools on the TUFLOW FV Wiki area also provided below:
<ol>
<li> [https://fvwiki.tuflow.com/index.php?title=SWAN_GIS_Model_Builder SWAN GIS Model Builder]
<li> [https://fvwiki.tuflow.com/index.php?title=SWAN_GIS_Post_Processing SWAN GIS Post Processing]
</ol>
=== Processing Toolbox ===
<ol>
<li> [[Convert_TUFLOW_Model_GIS_Format | Convert TUFLOW Model GIS Format]]
<li> [[Create_TUFLOW_Project | Create TUFLOW Project]]
<li> [[Package_Model_in_QGIS | Package Model]]
<li> [[QGIS_TIN_Polygons_Assign_Elevations | TIN Polygons - Assign Elevations]]
<li> SWMM Tools:
<ol><li>[[QGIS_SWMM_BC_Create_Channel_Endpoint_1D/2D_Connections | BC - Create channel endpoint 1D/2D connections]]
<li> [[QGIS_SWMM_Conduits_Assign_Losses | Conduits - Assign losses]]
<li> [[QGIS_SWMM_Conduits_Assign_Node_Fields | Conduits - Assign node fields]]
<li> [[QGIS_SWMM_Convert_ESTRY_Layers_To_SWMM | Convert - ESTRY layers to SWMM]]
<li> [[QGIS_SWMM_Convert_XPSWMM_GIS_Inlet_Layers_to_SWMM | Convert - XPSWMM GIS inlet layers to SWMM]]
<li> [[QGIS_SWMM_Convert_XPSWMM_Hydrology_(beta) | Convert - XPSWMM Hydrology (beta)]]
<li> [[QGIS_SWMM_Convert_XPSWMM_Model_From_XPX | Convert - XPSWMM model from XPX (beta)]]
<li> [[QGIS_SWMM_GeoPackage_Add_Sections | GeoPackage - Add sections]]
<li> [[QGIS_SWMM_GeoPackage_Create | GeoPackage - Create]]
<li> [[QGIS_SWMM_GeoPackage_Create_from_SWMM_inp | GeoPackage - Create from SWMM inp]]
<li> [[QGIS_SWMM_GeoPackage_Write_to_SWMM_inp | GeoPackage - Write to SWMM inp]]
<li> [[QGIS_SWMM_Integrity_Make_Object_Names_Unique| Integrity - Make object names unique]]
<li> [[QGIS_SWMM_Junctions_Convert_HX_Nodes_to_Storage| Junctions - Convert HX nodes to storage]]
<li> [[QGIS_SWMM_Junctions_Downstream_Junctions_to_Outfalls| Junctions - Downstream junctions to outfalls]]
<li> [[QGIS_SWMM_Junctions_Set_Attributes| Junctions - Set attributes]]
<li> [[QGIS_SWMM_Outfalls_Fix_Multiply_Connected_Links| Outfalls - Fix multiply connected links]]

</ol>
</ol>

If you encounter any issues with the plugin please contact [mailto:support@tuflow.com support@tuflow.com]. 
 

=Error While Upgrading Plugin=
[[File:Plugin_uninstall_failed.PNG]] 
If you receive an error while trying to upgrade the TUFLOW plugin you may need to either: 
<ol>
<li> Restart QGIS and try upgrading the plugin again
<li> Manually remove the old version
</ol>

Errors are most likely caused by an issue with deleting the old version of the plugin as some part of the plugin is still being used somewhere in memory (RAM) and locking permissions. This is a known issue that occur with the ReFH2 to TUFLOW tool in older versions of the plugin. Simply restarting QGIS and retrying the upgrade process should fix the issue.

=== Manually removing the TUFLOW plugin ===
To manually remove the TUFLOW plugin simply delete the 'tuflow' folder from the QGIS plugin directory (you may need to close QGIS first): 
<ol>
<li>'''Windows''' - %appdata%\QGIS\QGIS3\profiles\default\python\plugins
<li>'''Linux''' - /home/USER/.local/share/QGIS/QGIS3/profiles/default/python/plugins
</ol>

=Changelog=

[https://docs.tuflow.com/qgis-tuflow-plugin/changelog/ https://docs.tuflow.com/qgis-tuflow-plugin/changelog/]

 
{{Tips Navigation
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TUFLOW 2D Hydraulic Structures

2026-04-08T05:53:36Z

Emilie Nielsen: /* 2D BG Shape (2d_bg) */

= 2D Structure Modelling Theory =
The theory behind the modelling of energy losses and affluxes of hydraulic structures is presented in the following webinars by Bill Syme and Greg Collecutt (TUFLOW Developers).

*[https://www.tuflow.com/library/webinars/#structures Webinar Link: Modelling Energy Losses at Structures] 
*[https://www.tuflow.com/library/webinars/#nov2022_hydraulic_modelling_bridge Webinar Link: 1D, 2D & 3D Hydraulic Modelling of Bridges]
 

= 2D Bridge Modelling in TUFLOW - Overview =
The TUFLOW 2D solution explicitly predicts the majority of “macro” losses due to the expansion and contraction of water through a constriction, or around a bend, provided the resolution of the grid is sufficiently fine ([https://www.tuflow.com/Download/Publications/Flow%20Through%20an%20Abrupt%20Constriction%20-%202D%20Hydrodynamic%20Performance%20and%20Influence%20of%20Spatial%20Resolution,%20Barton,%202001.pdf Barton, 2001]; [https://www.tuflow.com/Download/Publications/Modelling%20of%20Bends%20and%20Hydraulic%20Structures%20in%20a%202D%20Scheme,%20Syme,%202001.pdf Syme, 2001]; [https://www.tuflow.com/Download/Technical_Memos/Modelling%20Bridge%20Piers%20in%202D%20using%20TUFLOW.pdf Ryan, 2013]). Where the 2D model is not of fine enough resolution to simulate the “micro” losses (e.g. from bridge piers, vena contracta, losses in the vertical (3rd) dimension), additional form loss coefficients and/or modifications to the cells widths and flow height need to be added.
==Contraction/Expansion Losses (“Macro” Losses)==
Loss of energy is caused by the flow contraction during the expansion of water after the vena-contracta inside a bridge section and the flow expansion downstream a bridge. As discussed above, this type of "macro" losses can be explicitly resolved by the TUFLOW 2D solver, provided that a proper turbulence model and mesh size are used. Below is an example of the 2D modelling of flow contraction/expansion at a pair of bridge abutments.
 
[[File:FC_Velocity_Example.PNG|600px]] 

==Pier Losses==
Piers are usually smaller than the 2D cell size in real-world flood models. Although flexible mesh solver or quadtree refinement can be applied to reduce the local cell size around the pier, it also comes with an expensive computational cost that could significantly increase the simulation time. More practically, the backwater effect of piers can be modelled as sub-grid form losses.

Pier form loss coefficients can be derived from information in publications such as [https://www.fhwa.dot.gov/engineering/hydraulics/library_arc.cfm?pub_number=1&id=5 ''Hydraulics of Bridge Waterways'' (Bradly, 1978)] or [https://austroads.com.au/publications/bridges/agbt08 ''Guide to Bridge Technology Part 8: Hydraulic Design of Waterway Structures'' (AUSTROADS, 2018)]. Energy loss estimated from bridge piers or other obstructions, vertical or horizontal, that do not cause upstream controlled flow regimes like pressure flow, are dependent on the ratio of the obstruction's area perpendicular to the flow direction to the gross flow area of the bridge opening, the shape of the piers or obstruction, and the angularity of the piers/obstruction to the flow direction. For example, using Hydraulics of Bridge Waterways (Bradly, 1978) the approach is:
<ol>
<li>Calculate the ratio of the water area occupied by piers to the gross water area of the constriction (both based on the normal water surface) and the angularity of the piers. These inputs are used to calculate "J" in the FHA documentation.</li>
<li>Use the Figure 4.10 ''Incremental Backwater Coefficient for Piers'' data to calculate Kp. 
[[File:incremental_backwater_coefficient_2018_pier_losses.png]]
 
'''NOTE''': the pier form loss coefficients in Hydraulics of Bridge Waterways are derived based on the cross-sectional averaged velocity through the bridge opening in the absence of piers. It's not necessary to specify a blockage value if a pier form loss coefficient estimated from this method is used.
</li>
</ol>

==Bridge Deck and Rail (Super Structure)==
When a bridge deck become partially or completely submerged, the deck could generate extra afflux resulting in increased water levels and flood extents upstream of the structure. The flow around the deck is highly 3-dimentional and complexed due to the different deck designs/profiles and/or the occurrence of pressure flow. In 2D SWE solver, depth-varying form loss values are often needed to reproduce the afflux caused by such structure. Due to the complexity of the flow, guidelines on how to set the form loss coefficient for the bridge deck are rare. We have carried out a joint research with QLD TMR (Queensland Department of Transport and Main Roads) regarding how to choose a proper form loss value for the bridge deck [https://tuflow.com/media/7554/2022-bridge-deck-afflux-modelling-benchmarking-of-cfd-and-swe-codes-to-real-world-data-collecutt-et-al-hwrs.pdf (Collecutt et al, 2022)] . In the research, CFD modelling was conducted to investigate the characteristics of energy loss of a simple bridge with a flat bottomed deck and guardrails.
 
[[File:CFD_study.png|600px]]

Below are the key findings from the study:
*The results displayed a characteristic shape for head loss coefficient as a function of downstream water level over the deck thickness (TW/T).
*The head loss (afflux) peaks when the water level is approximately 1.6*T above the bridge soffit, and decays slowly as the bridge becomes progressively drowned out.
[[File:FormLoss_vs_TWT.png|600px]]
 

=== Bridge Design (hB/T) vs Form Loss Coefficient Table===
The peak loss coefficient value is a function of the ratio of the depth underneath the deck (hB) and the thickness of the deck (T). This table can be used to estimate the deck form loss coefficient based on the bridge design (hB/T).
<ol>
{| style="text-align: center;" class="wikitable" width="35%"
! style="background-color:#005581; font-weight:bold; color:white;" width=55%| Deck Height to Thickness Ratio
! style="background-color:#005581; font-weight:bold; color:white;" width=45%| Peak Form Loss Coefficient
|-
| Scenario A (hB/T) = 2 || 0.42
|-
| Scenario B (hB/T) = 4 || 0.28
|-
| Scenario C (hB/T) = 6 || 0.20
|}
</ol>

*The solid portion of the guard rails (blockage * rail depth) can be added to T in addition to the deck thickness to calculate hB/T.
*For bridge with more complicated designs (e.g. girders), higher form loss might be required due to the higher surface roughness of the bridge.
*If the hB/T ratio is less than 2 or greater than 6, use a peak form loss coefficient of 0.42 (minimum) or 0.20 (maximum), respectively.

'''NOTE''': This form loss value should not be confused with the value of 1.56 used in the pressure flow approached adopted in [[1D_Bridges | TUFLOW 1D "B" and "BB" bridge]]. TUFLOW 1D bridge pressure flow approach is based on the section 4.13.2 "All Girders in Contact with Flow (Case II)" of ''Guide to Bridge Technology Part 8: Hydraulic Design of Waterway Structures'' (AUSTROADS, 2018). The original hydraulic experiment conducted by [https://hdl.handle.net/10217/39009 Liu et al (1957)] in a laboratory flume with a pair of bridge abutments and a deck. The flow conditions were similar to orifice flow due to the high blockage ratio caused by the abutments and the deck. When modelling bridges in 2D, the contraction/expansion losses caused by the abutments would be handled explicitly by the 2D solver, so a value 1.56 can lead to duplication of the contraction/expansion losses caused by the bridge abutments. 
 

=TUFLOW 2D Bridge Setup=
There are two methods available to model depth varying form loss of a bridge structure:
* [[TUFLOW_2D_Hydraulic_Structures#2D_Layered_Flow_Constriction_.282d_lfcsh.29 |2D Layered Flow Constriction (2d_lfcsh)]]
:The traditional method used to model depth-varying form loss through bridge components such as piers, decks, and rails.

*[[TUFLOW_2D_Hydraulic_Structures#2D_BG_Shape_.282d_bg.29 |2D BG Shape (2d_bg)]] (introduced in the 2023 release)
:A simplified approach developed to simplify the model input based on the findings from the joint TMR Study [https://tuflow.com/media/7554/2022-bridge-deck-afflux-modelling-benchmarking-of-cfd-and-swe-codes-to-real-world-data-collecutt-et-al-hwrs.pdf (Collecutt et al, 2022)].

Both methods provide options for representing flow surcharging, the pressure flow of bridge decks and eventually submerged bridge flow at higher water levels. During the surcharging of bridge decks, higher energy losses can be specified to simulate the pressure flow.

Examples for how to configure both approaches are provided in the 2D structures section of the [[TUFLOW_Example_Models#2D_Structures |TUFLOW Wiki Example Models]] and [[Tutorial_M04 |Tutorial Module 4]] - 2D Bridges.

==2D Layered Flow Constriction (2d_lfcsh)==
Four flow constriction layers are represented in a 2d_lfcsh layer. The lower three layers represents the pier, the bridge deck and the rails. Each layer has its own attributes to specify the blockage and the form loss coefficient. The top (fourth) layer assumes the flow is unimpeded, representative of flow over the top of a bridge. Within the same shape, the invert of the bed, and thickness of each layer can vary in 3D.

The following table provides an overview for how to determine the blockage and form loss coefficient for each layer: 
{| style="text-align: left; margin-left: 0; " class="wikitable" width="80%"
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Layer
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Description
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Blockage (%)
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Form Loss Coefficient (FLC)
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Notes
|-

| 1 || Pier layer || ~5% (can be omitted if included in FLC) || Estimate using [[TUFLOW_2D_Hydraulic_Structures#Pier_Losses | Pier Losses]] || Represents flow obstruction from piers beneath the bridge deck
|-
| 2 || Bridge deck || 100% || Use calibration data, if available, to determine FLC. If no calibration is available, estimate using [[TUFLOW_2D_Hydraulic_Structures#Bridge_Design_.28hB.2FT.29_vs_Form_Loss_Coefficient_Table | hB/T vs FLC]] table || Full blockage, no flow through the deck
If using the [[TUFLOW_2D_Hydraulic_Structures#Bridge_Design_.28hB.2FT.29_vs_Form_Loss_Coefficient_Table | hB/T vs FLC]] table, it is recommended to enable the Method C Form Loss Approach
|-
| 3 || Bridge rails || 10% – 100% || Use calibration data, if available, to determine FLC. 
If no calibration data is available, combined FLC for Layers 2 and 3 should be estimated using the [[TUFLOW_2D_Hydraulic_Structures#Bridge_Design_.28hB.2FT.29_vs_Form_Loss_Coefficient_Table | hB/T vs FLC]] table, where T = L2_Depth + (pBlockage × L3_Depth)
*(pBlockage × L3_Depth) represents the solid portion of the rails
*L2 FLC and L3 FLC should sum to the combined FLC
|Blockage and FLC depends on rail type Sensitivity testing with 100% blockage is recommended due to potential for debris during flood
If using the [[TUFLOW_2D_Hydraulic_Structures#Bridge_Design_.28hB.2FT.29_vs_Form_Loss_Coefficient_Table | hB/T vs FLC]] table, it is recommended to enable the Method C Form Loss Approach
|-
| 4 || Above rails || 0% || 0 || Represents unimpeded overtopping flow
|}
<ol>
[[File:2d_lfcsh_attributes.png | 500px ]]
</ol>
 

===Blockage===

The 2d_lfcsh functions by adjusting the flow width and the form loss of 2D cell faces. The combined blockage across the 4 layers is calculated at each simulation timesteps:
<ol>
 
[[File: Blockage_total_equation_01.png|600px]]
 
where 
'''''yi''''' is the actual depth of water in layer '''''i''''' 
'''''ytotal''''' is the total water depth 
</ol>

===Form Loss Approach===

The combined form loss coefficient is determined using one of three methods. The form loss coefficient method can be specified either individually using the 2d_lfcsh “Shape_Options” attribute or globally using the .tcf command: 
<tt>Layered FLC Default Approach == [ METHOD A | {METHOD B} | METHOD C | METHOD D]</tt> 

:METHOD A: The losses are accumulated as the water level rises through the layers. 
<ol>
[[File:Eq_flc_cumulate.png |450px]]
</ol>
:*Layer 1: Constant form loss (L1_FLC)
:*Layers 2 & 3: Form loss increases based on the depth of water in layer 2 & 3; peak form loss at top of Layer 3
:*Above Layer 3: Applies the full accumulated form loss continuously, even when overtopping begins (no reduction)
:Note: Simpler method but tends to overestimate losses when the structure is submerged or overtopped 

:METHOD B (default): the losses are applied pro-rata according to the depth of water in each layer. 
<ol>
[[File:Eq_flc_portion.png |430px]]
</ol>
:*Layer 1: Constant form loss (L1_FLC)
:*Layers 2 & 3: Form loss increases based on the depth of water in layer 2 & 3; peak form loss at top of Layer 3
:*Above Layer 3: Total form loss gradually reduces as water overtops the structure
:Note: Maintains backward compatibility but may underrepresent losses during pressurised or overtopped flows 

:METHOD C (recommended): hybrid approach combining Method A and Method B. 
<ol>
[[File:Eq_flc_methodC.png |520px]]
</ol>
:*Layer 1: Constant form loss (L1_FLC)
:*Layers 2 & 3: Gradual increase in form loss with water level, following Method A
:*Above Layer 3: Total form loss gradually reduces as water overtops the structure, following Method B
:Note: Recommended method; aligns closest to CFD modelling results and TUFLOW HPC behaviour.

:METHOD D: Allows the modeller to control the depth at which the losses start to reduce when the flow transitions between pressure flow and drowned flow.
:This approach is the same used by the 2d_bg layer (introduced in the 2023-03 release). It is recommended to use the 2d_bg layer as it has the benefit of a simplified attribute table, for easier user input.

===Form Loss Calibration Example - Iowa River Flood Study===

In this study, a combined form loss coefficient of 0.35 was used to match observed head loss during slight overtopping of a bridge. The FLC values for each layer were adjusted to achieve the correct combined form loss. The table and plot show how each layer contributes to the total form loss and highlight the differences in calculated form loss between the three methods.

{| style="text-align: left; margin-left: 0;" class="wikitable" width="60%"
!colspan="1" rowspan="2" style="background-color:#005581; font-weight:bold; color:white;" width=6%| Layer
!colspan="1" rowspan="2" style="background-color:#005581; font-weight:bold; color:white;" width=10%| Depth (m)
!colspan="1" rowspan="2" style="background-color:#005581; font-weight:bold; color:white;" width=12%| Blockage (%)
!colspan="2" style="background-color:#005581; font-weight:bold; color:white;" width=20%| Method A
!colspan="2" style="background-color:#005581; font-weight:bold; color:white;" width=20%| Method B
!colspan="2" style="background-color:#005581; font-weight:bold; color:white;" width=20%| Method C
|-
! style="background-color:#005581; font-weight:bold; color:white;"| Layer FLC
! style="background-color:#005581; font-weight:bold; color:white;"| Combined FLC
! style="background-color:#005581; font-weight:bold; color:white;"| Layer FLC
! style="background-color:#005581; font-weight:bold; color:white;"| Combined FLC
! style="background-color:#005581; font-weight:bold; color:white;"| Layer FLC
! style="background-color:#005581; font-weight:bold; color:white;"| Combined FLC
|-
| 1 || 5.0 || 5 || 0.07 || 0.07 || 0.07 || 0.07 || 0.07 || 0.07
|-
| 2 || 1.5 || 100 || 0.15 || 0.22 || 1.05 || 0.30 || 0.15 || 0.22
|-
| 3 || 1.0 || 50 || 0.13 || 0.35 || 0.70 || 0.35 || 0.13 || 0.35
|}

</ol>
 
<ol>
[[File:FLC_vs_height_updated.png | 600px ]]
</ol>

==2D BG Shape (2d_bg)==
2D BG Shape is similar to the Layered Flow Constriction, but has several updates to simplify the input based on the findings from the joint study with TMR [https://tuflow.com/media/7554/2022-bridge-deck-afflux-modelling-benchmarking-of-cfd-and-swe-codes-to-real-world-data-collecutt-et-al-hwrs.pdf (Collecutt et al, 2022)].

The following table provides an overview of how to determine the blockage and form loss coefficient for each layer: 
{| style="text-align: left; margin-left: 0; " class="wikitable" width="80%"
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Layer
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Description
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Blockage (%)
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Form Loss Coefficient (FLC)
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Notes
|-

| 1 || Pier layer || ~5% (can be omitted if included in FLC) || Estimate using [[TUFLOW_2D_Hydraulic_Structures#Pier_Losses | Pier Losses]] || Represents flow obstruction from piers beneath the bridge deck
|-
| 2 || Bridge deck || 100% || rowspan="2" | The Super Structure (Super_S) is the bridge deck and rails layers combined. 
Use calibration data, if available, to determine FLC. 
If no calibration data is available, the Super_S FLC should be estimated using the [[TUFLOW_2D_Hydraulic_Structures#Bridge_Design_.28hB.2FT.29_vs_Form_Loss_Coefficient_Table | hB/T vs FLC]] table, where T = Deck_Depth + (Rail_pBlockage*Rail_Depth)
*(Rail_pBlockage*Rail_Depth) represents the solid portion of the rails
|| Full blockage, no flow through the deck
|-
| 3 || Bridge rails || 10% – 100% || Sensitivity testing with 100% blockage is recommended due to potential for debris during flood events
|-
| 4 || Above rails || 0% || 0 || Represents unimpeded overtopping flow
|}

<ol>
[[File:Bridge block.jpg | 800px]]
</ol>

===Inflection Point===

Based on findings from the joint study [https://tuflow.com/media/7554/2022-bridge-deck-afflux-modelling-benchmarking-of-cfd-and-swe-codes-to-real-world-data-collecutt-et-al-hwrs.pdf (Collecutt et al, 2022)], the head loss peaks when the water level is approximately 1.6*T above the bridge soffit, and decays slowly as the bridge becomes progressively drowned out. The 'SuperS_IPf' attribute (inflection point factor, default = 1.6) can be used to define the height of the inflection point. The solid portion of the rail layer is also added to the deck thickness to calculate the depth to the inflection point (DIP), i.e.:
<ol>
[[File:eq_flc_bg_infection_point.png | 520px ]]
</ol>

===Form Loss Approach===
The form loss approach is similar to the FLC approach METHOD C, with L2/L3 replaced by a single super structure layer:
<ol>
[[File:eq_flc_bg.png | 480px ]]
</ol>

===Form Loss Calibration Example - Iowa River Flood Study===
This example uses the same bridge setup described in the[[TUFLOW_2D_Hydraulic_Structures#Form_Loss_Calibration_Example_-_Iowa_River_Flood_Study | 2D Layered Flow Constriction]] section, with the following parameters applied:
*SuperS_FLC = 0.28
*SuperS_Ipf = 1.6,
The Depth to Inflection Point (DIP) is calculated as 3.2m above the bridge soffit.

The table and figure below show how the form loss value varies with water depth.
<ol>
{| style="text-align: center;" class="wikitable" width="32%"
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;" width=8%| Layer
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;" width=8%| Depth (m)
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;" width=8%| Blockage (%)
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;" width=8%| Form Loss
|-
| Pier || 5.0 || 5 || 0.07
|-
| Deck || 1.5 || 100 || rowspan="2" | 0.28
|-
| Rail || 1.0 || 50
|}

[[File:FLC_vs_height_bg.png | 600px ]]
</ol>

== 2D Bridges Line vs Polygon Layer ==
The form loss coefficient (FLC) is applied differently when using a line compared to a polygon for both 2d_lfcsh and 2d_bg inputs. The FLC is applied at cell sides (u and v faces) as this is where velocities are calculated. 
For larger bridges that spread across multiple cells, it is recommended to use a polygon layer, which selects all u and v faces falling within the polygon.
 
 
'''2D Layered Flow Constriction (2d_lfcsh)'''
{| style="text-align: left; margin-left: 0;" class="wikitable" width="80%"
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 7.5%;"| Geometry
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 7.5%;"| Line Type
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 11%;"| Width Attribute
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 22%;"| FLC Input
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 22%;"| FLC Applied
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 30%;"| Notes
|-
!rowspan="3" | Line
| Thin
| zero
| Total form loss of the bridge
| Applies the FLC to a single row of cell sides
| This approach is cell size independent. It is the easiest setup and the preferred / recommended approach when using 2d_lfcsh.
|-
| Thick
| between zero and 1.5 times the cell size
| Total form loss of the bridge
| FLC/2 applied to all sides of the selected cells
| A cell is selected if the polyline intersects the cell crosshair. Caution should be taken when using a "thick" line, as changes in cell size can cause it to become a "wide" line. If this occurs, the FLC attribute may need to be recalculated to avoid overestimating or underestimating losses.
|-
| Wide
| larger than 1.5 times the cell size
| Total form loss of the bridge ''(may need to be recalculated, see notes)''
| FLC divided by number of cell sides in the direction of flow 
''(number of cell sides in the direction of flow is calculated as line width divided by cell size)''
| Polygon shapes are recommended if more than 3 rows of faces must be selected.. 
Caution should be taken when using a "wide" line. The cell size and alignment of the 2d_lfcsh line may result in selecting too many or too few cell faces in the direction of the flow. The FLC input may need to be recalculated to ensure FLC Applied multiplied by the number of cell sides in the direction of flow equates to the intended total form loss.
|-
!rowspan="1" | Polygon
| -
| -
| Total loss per unit length (meters or feet) in the direction of flow
| FLC * cell size applied to all sides of selected cells
|
|}

'''2D Bridge (2d_bg)'''
{| style="text-align: left; margin-left: 0;" class="wikitable" width="80%"
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 7.5%;"| Geometry
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 7.5%;"| Line Type
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 11%;"| Width Attribute
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 22%;"| FLC Input
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 22%;"| FLC Applied
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 30%;"| Notes
|-
!rowspan="3" | Line
| Thin
| zero
| Total form loss of the bridge
| Applies the FLC to a single row of cell sides.
| This approach is cell size independent.
|-
| Thick
| larger than zero
| Total form loss of the bridge
| FLC/2 applied to all sides of the selected cells
| This approach is cell size independent. A cell is selected if the polyline intersects the cell crosshair.
|-
| Wide
| Not supported
| –
| –
| BG polygon shapes are recommended if more than 3 rows of faces must be selected.
|-
!rowspan="1" |Polygon
| -
| ''(used to automatically distribute the total FLC to the selected faces)''
| Total form loss of the bridge
| FLC / Deck_Width * cell size applied to all sides of selected cells
| For bridges modelled using a 2d_bg polygon the relative ratio of the bridge width to the 2D cell size should be 4 or greater. For more information on this see [https://downloads.tuflow.com/Other/2d_bg_R_Bridge_Configuration_Advice_202503.pdf 2d_bg_R_Bridge_Configuration_Advice.pdf].
|}
 
The following diagrams demonstrate how the input FLC is applied for the four geometry options for 2d_lfcsh and 2d_bg layers: 
[[File:2dlfcsh 2dbg combined v2.png|1200px]]

It is good modelling practice to check the [[Check_Files_2d_lfcsh_uvpt | lfcsh_uvpt_check]] and [[Check Files 2d bg uvpt check | bg_uvpt_check]] files to confirm the number of faces selected and the FLC values assigned. It is also strongly recommended to undertake a sensitivity analysis on the applied form losses in the model to check if it makes any difference to the results and/or double check against other methods (hand calculations, other software, CFD modelling), especially if the bridge is near an area of interest. If calibration data is available, this should be used to guide the form loss value specification. 
 

= Common Questions Answered (FAQ)=
== What blockage values should I use for bridge guard rails? ==
The blockage of bridge guard rails can be anything from 100% blocked (solid concrete rails) to 10% blocked (very open rails). In addition, the accumulation of debris during a flood can be substantial as shown in the image below. Sensitivity testing with 100% blockage is recommended.
 
[[File:Bridge rail debris.jpg | 500px]]

== How to conduct sensitivity test for 2D bridges? ==
General recommendations to cross-check the results are:
* Compare computed affluxes against desktop methods (e.g. Hydraulics of Bridge Waterways, 1978) and/or other software including CFD, especially for unusual bridge designs.
* Use any recorded flood marks or general observations from past events to check and calibrate FLC values.
* Conduct sensitivity testing by assessing the impact and influence of FLC values on your modelling objectives. The afflux resulting from the FLC values will be proportional to the velocity head, i.e. ∆h=FLC*(v^2/2g). As such, if velocities are low (e.g. 1 m/s), the results may not be overly sensitive to uncertainties in the FLC values. If completing a check using this equation for a long skew bridge it is best to calculate the total structure velocity from a PO line digitised in the same location as the bridge.

Finally, after completing sensitivity testing and understanding the range of uncertainty due to unknowns like the degree of blockage and influence of FLC values (e.g. +/-20%), you are in a position to discuss with your client how best to proceed. For example, if the modelling is to set planning levels for a development upstream then it may be appropriate to choose values on the higher side (higher FLC values and/or blockage assumptions), noting that the uncertainty may be amply covered by a regulatory freeboard. Conversely, if the development is on the downstream side the conservative approach would be to use the results at the lower end of your FLC/blockage values. 
[[File:Bridge Flood Debris Loading.jpg | 500px]] 

== Should I use both FLC and blockage for layer one in 2D bridge layered flow constriction? ==
When applying FLC and blockage values to model obstructions such as piers, the following considerations need to be taken into account:
* The FLC value applies an energy loss along 1D channels or across 2D cell faces equivalent to FLC*V2/2g where V is the 1D channel velocity or the 2D cell face velocity.
* FLC values are often sourced from publications such as Hydraulics of Bridge Waterways or AustRoads (e.g. Kp chart for piers).
* If possible, establish whether the source of the FLC value is based on the approach velocity (the velocity in the absence of piers) or structure velocity (the velocity with area blocked out by the piers) noting that it often isn’t clear or stated.
** If it is the structure velocity, this is usually the velocity at the vena-contracta (point of greatest contraction within the entrance to the structure and therefore highest velocity) - see image below. Bluff or sharp-edged obstructions will have a much more pronounced vena-contracta, and therefore higher velocity compared with a round-edged obstruction.
** FLC values based on the approach velocity will be higher than those based on the structure velocity to achieve the same energy loss.
* Applying a blockage equivalent to the obstruction width will increase, usually very slightly, the velocity of the 1D channel or 2D cell face. This won’t be the vena-contracta velocity, but a velocity between the approach velocity and the vena-contracta velocity. A greater blockage will need to be applied to emulate the vena-contracta velocity.
* If the FLC source value is based on:
** The approach velocity then there is no need to apply a blockage value.
** The structure velocity then the blockage value should be applied noting that it may be appropriate to apply a larger blockage to take into account the vena-contracta.
* If it is not clear or unknown whether the FLC source value is based on the approach or structure velocity, the recommendation would be to apply the blockage in the interests of being slightly conservative on the upstream flood level calculation.
* For most minor obstructions such as bridge piers, the blockage is usually relatively small and whether included or not has a negligible or minor affect on flood levels compared with other factors such as the approach embankments and the bridge deck.
* Blockage from debris wrapped around piers can have a greater influence on the results than the effect of applying or not applying a blockage. Debris wrapped around piers can be accounted for in the FLC value calculated for the pier layer.
* As always, sensitivity testing with and without blockage and +/- the FLC value is highly recommended to understand their importance in regard to the broader modelling objectives and the effects of uncertainties in the input data, boundaries, other parameters such as Manning’s n values, and the accuracy of the numerical solution scheme (see [https://www.tuflow.com/library/webinars/#maximise_accuracy Maximising the Accuracy of Hydraulic Models webinar]).
[[File: Vena_contracta.png]] 
''Image showing the formation of the vena-contracta.'' 
 

==I don't see results that I expect when using 2d_lfcsh layer==
The 2d_lfcsh layer is a versatile feature that was designed to model bridges in 2D, but can also be used for other applications like fences, buildings raised on pillars and so on.
Some of the unexpected results could be:
* Water level going through the bridge deck in 2D map output.
* Water transiting through 100% blocked Layer 1, e.g. fences with solid base.
* SHMax.csv reporting values above the bridge deck when 2D map output reports water level lower than the top of the bridge deck.

TUFLOW is a 2D solution (not 3D), in the 2d_lfcsh layer the percent blockage and form loss coefficient applied to the cell faces is depth averaged across the entire cell face (across Layer 1, 2 and 3): 
*For bridges, where Layer 2 has a 100% blockage applied, the minimum flow width of 0.001m is used and is averaged with the Layer 1 blockage (based on the depth of the water). This may result in a water level being reported within or above the bridge deck, which would represent the pressure head.
*Layered flow constriction works by adjusting the flow area of the cell faces by any blockages to generate the correct depth averaged velocity at each face at which the form losses are applied as a fraction of the V2/2g kinetic energy. Calculating the correct velocity is critical for determining the losses as the losses are proportional to the velocity squared. 
*For a layered flow constriction cell face the flow area cannot be zero above the invert of Layer 1 to avoid a divide by zero in the computations, therefore a minimum average flow width after applying blockages of 0.001 m is applied. if Layer 1 is 100% blocked, a very small amount of water will flow through Layer 1. If this is unacceptable, instead of applying 100% blockage of Layer 1, the preferred approach is to start the layered flow constriction at the top of Layer 1 or raise the ground elevation to the top of Layer 1 using one of the Z Shape modification functions (e.g. a breakline). 
<ol>
[[File:100% Blockage Diagram.png | 500px]]
</ol>

== Can I model bridge piers explicitly in 2D using very small cells? ==
It isn't recommended to explicitly model bridge piers by blocking out the pier faces in TUFLOW, or in any hydraulic modelling software based on solving Shallow Water Equations(SWE). Due to the 3-dimentiality of the flow and turbulence around a pier, computational fluid dynamics (CFD) approach is often required to simulate the flow around piers explicitly. The wake turbulence behind a simple-shape pier can be resolved to some extent using extremely fine mesh in TUFLOW (see calibration example to a flume experiment in the [https://www.tuflow.com/library/webinars/#structures webinar on Energy Losses at Structures]), however the predictions for head losses show notable sensitivities to the mesh size, the mesh design, and the choice of turbulence model. The extremely fine mesh resolution also results in significantly higher computational costs.

Therefore, the safest and strongly recommended approach with regard to establishing head losses and consequently flood levels, is to model the effects of such obstructions with form loss coefficients (applied to selected mesh cells) that have been derived from physical testing. This approach has been shown to provide the most consistent results across various mesh resolutions. It also has the added benefit that, by avoiding small cells in the mesh, it will provide much more efficient run times for flow solvers.

[[File:Flow round a cylinder.png]]

''The point of flow separation around an object has a major bearing on the drag coefficient and is not reliably reproduced by 2D or 3D software.''


== How to best convert flow constriction data (2d_fc or 2d_fcsh) into newer formats (2d_lfcsh or 2d_bg)? ==
The form loss parameters can be transferred from the flow constriction (2d_fc or 2d_fcsh) to the first layer of the layered flow constriction (2d_lfcsh) or pier layer of the 2d_bg. Definition of the remaining form loss and blockage layer inputs should follow the guidance outlined in [[TUFLOW_2D_Hydraulic_Structures#2D_Layered_Flow_Constriction_.282d_lfcsh.29 | 2D Layered Flow Constriction]] and [[TUFLOW_2D_Hydraulic_Structures#2D_BG_Shape_.282d_bg.29 | 2D BG Shape]] paragraphs. 
When using floating pontoon (type FD in the 2d_fc or 2d_fcsh) different setup might need to be used for different events. For large events when floating pontoon becomes fixed at the top of the supporting piles, standard 2d_lfcsh setup can be used. Smaller events when the pontoon is floating at different heights might require more sensitivity testing of the structure parameters to find out a setup the matches the reality as close as possible. 

== Should I model bridges in 1D or 2D Domain? ==
The recommended approach typically depends on the study objectives and if the channel upstream and downstream of the bridge is modelled in 1D or 2D. To preserve the momentum as accurately as possible the bridge should be modelled in the same dimension as the channel, e.g. 1d_nwk bridge if the channels is in 1D and 2d_bg or 2d_lfcsh if the channel is modelled in 2D. 
In 2D, the expansion/contraction losses are modelled based on the topography and don't need to be estimated as attributes as for 1D modelling. Also, for higher flows where the bridge is overtopped, 2D is preferable approach.

== What is the difference between downstream and upstream controlled flow? ==
Downstream control means a change in downstream water level will cause a change in upstream water level. Upstream control means the upstream water level is insensitive to the downstream water level and usually indicates the occurrence of supercritical flow.

== What FLC values should be used for 2d_bg bridge if hB/T is below 2 or above 6? ==
TMR has extended the CFD simulation to hB/T ratios of 1 to 10. Refer to the [https://docs.tuflow.com/classic-hpc/manual/latest/ TUFLOW Manual] for details.

If hB/T is outside this ratio:
* hB/T ratios of less than 1 represent a very unusual bridge sitting low to the ground, and the peak FLC may increase above the end value (FLC of 0.6) in a way that doesn't follow the research trend or extrapolation. For these cases we would recommend using CFD modelling to obtain a more informed value. Alternatively, computing an FLC based on pressure flow or using 1D culvert might be considered.
* For hB/T ratios of greater than 10, the FLC is likely to continue to decrease, but probably not significantly. Clamping to the end value (FLC of 0.16) might be considered the more conservative approach (if the primary concern is flood levels upstream of the bridge). 
 
{{Tips Navigation
|uplink=[[ TUFLOW_Modelling_Guidance | Back to TUFLOW Modelling Guidance]]
}}

File:Bridge block.jpg

2026-04-08T05:52:37Z

Emilie Nielsen:

TUFLOW 2D Hydraulic Structures

2026-04-08T05:47:37Z

Emilie Nielsen: /* Pier Losses */

= 2D Structure Modelling Theory =
The theory behind the modelling of energy losses and affluxes of hydraulic structures is presented in the following webinars by Bill Syme and Greg Collecutt (TUFLOW Developers).

*[https://www.tuflow.com/library/webinars/#structures Webinar Link: Modelling Energy Losses at Structures] 
*[https://www.tuflow.com/library/webinars/#nov2022_hydraulic_modelling_bridge Webinar Link: 1D, 2D & 3D Hydraulic Modelling of Bridges]
 

= 2D Bridge Modelling in TUFLOW - Overview =
The TUFLOW 2D solution explicitly predicts the majority of “macro” losses due to the expansion and contraction of water through a constriction, or around a bend, provided the resolution of the grid is sufficiently fine ([https://www.tuflow.com/Download/Publications/Flow%20Through%20an%20Abrupt%20Constriction%20-%202D%20Hydrodynamic%20Performance%20and%20Influence%20of%20Spatial%20Resolution,%20Barton,%202001.pdf Barton, 2001]; [https://www.tuflow.com/Download/Publications/Modelling%20of%20Bends%20and%20Hydraulic%20Structures%20in%20a%202D%20Scheme,%20Syme,%202001.pdf Syme, 2001]; [https://www.tuflow.com/Download/Technical_Memos/Modelling%20Bridge%20Piers%20in%202D%20using%20TUFLOW.pdf Ryan, 2013]). Where the 2D model is not of fine enough resolution to simulate the “micro” losses (e.g. from bridge piers, vena contracta, losses in the vertical (3rd) dimension), additional form loss coefficients and/or modifications to the cells widths and flow height need to be added.
==Contraction/Expansion Losses (“Macro” Losses)==
Loss of energy is caused by the flow contraction during the expansion of water after the vena-contracta inside a bridge section and the flow expansion downstream a bridge. As discussed above, this type of "macro" losses can be explicitly resolved by the TUFLOW 2D solver, provided that a proper turbulence model and mesh size are used. Below is an example of the 2D modelling of flow contraction/expansion at a pair of bridge abutments.
 
[[File:FC_Velocity_Example.PNG|600px]] 

==Pier Losses==
Piers are usually smaller than the 2D cell size in real-world flood models. Although flexible mesh solver or quadtree refinement can be applied to reduce the local cell size around the pier, it also comes with an expensive computational cost that could significantly increase the simulation time. More practically, the backwater effect of piers can be modelled as sub-grid form losses.

Pier form loss coefficients can be derived from information in publications such as [https://www.fhwa.dot.gov/engineering/hydraulics/library_arc.cfm?pub_number=1&id=5 ''Hydraulics of Bridge Waterways'' (Bradly, 1978)] or [https://austroads.com.au/publications/bridges/agbt08 ''Guide to Bridge Technology Part 8: Hydraulic Design of Waterway Structures'' (AUSTROADS, 2018)]. Energy loss estimated from bridge piers or other obstructions, vertical or horizontal, that do not cause upstream controlled flow regimes like pressure flow, are dependent on the ratio of the obstruction's area perpendicular to the flow direction to the gross flow area of the bridge opening, the shape of the piers or obstruction, and the angularity of the piers/obstruction to the flow direction. For example, using Hydraulics of Bridge Waterways (Bradly, 1978) the approach is:
<ol>
<li>Calculate the ratio of the water area occupied by piers to the gross water area of the constriction (both based on the normal water surface) and the angularity of the piers. These inputs are used to calculate "J" in the FHA documentation.</li>
<li>Use the Figure 4.10 ''Incremental Backwater Coefficient for Piers'' data to calculate Kp. 
[[File:incremental_backwater_coefficient_2018_pier_losses.png]]
 
'''NOTE''': the pier form loss coefficients in Hydraulics of Bridge Waterways are derived based on the cross-sectional averaged velocity through the bridge opening in the absence of piers. It's not necessary to specify a blockage value if a pier form loss coefficient estimated from this method is used.
</li>
</ol>

==Bridge Deck and Rail (Super Structure)==
When a bridge deck become partially or completely submerged, the deck could generate extra afflux resulting in increased water levels and flood extents upstream of the structure. The flow around the deck is highly 3-dimentional and complexed due to the different deck designs/profiles and/or the occurrence of pressure flow. In 2D SWE solver, depth-varying form loss values are often needed to reproduce the afflux caused by such structure. Due to the complexity of the flow, guidelines on how to set the form loss coefficient for the bridge deck are rare. We have carried out a joint research with QLD TMR (Queensland Department of Transport and Main Roads) regarding how to choose a proper form loss value for the bridge deck [https://tuflow.com/media/7554/2022-bridge-deck-afflux-modelling-benchmarking-of-cfd-and-swe-codes-to-real-world-data-collecutt-et-al-hwrs.pdf (Collecutt et al, 2022)] . In the research, CFD modelling was conducted to investigate the characteristics of energy loss of a simple bridge with a flat bottomed deck and guardrails.
 
[[File:CFD_study.png|600px]]

Below are the key findings from the study:
*The results displayed a characteristic shape for head loss coefficient as a function of downstream water level over the deck thickness (TW/T).
*The head loss (afflux) peaks when the water level is approximately 1.6*T above the bridge soffit, and decays slowly as the bridge becomes progressively drowned out.
[[File:FormLoss_vs_TWT.png|600px]]
 

=== Bridge Design (hB/T) vs Form Loss Coefficient Table===
The peak loss coefficient value is a function of the ratio of the depth underneath the deck (hB) and the thickness of the deck (T). This table can be used to estimate the deck form loss coefficient based on the bridge design (hB/T).
<ol>
{| style="text-align: center;" class="wikitable" width="35%"
! style="background-color:#005581; font-weight:bold; color:white;" width=55%| Deck Height to Thickness Ratio
! style="background-color:#005581; font-weight:bold; color:white;" width=45%| Peak Form Loss Coefficient
|-
| Scenario A (hB/T) = 2 || 0.42
|-
| Scenario B (hB/T) = 4 || 0.28
|-
| Scenario C (hB/T) = 6 || 0.20
|}
</ol>

*The solid portion of the guard rails (blockage * rail depth) can be added to T in addition to the deck thickness to calculate hB/T.
*For bridge with more complicated designs (e.g. girders), higher form loss might be required due to the higher surface roughness of the bridge.
*If the hB/T ratio is less than 2 or greater than 6, use a peak form loss coefficient of 0.42 (minimum) or 0.20 (maximum), respectively.

'''NOTE''': This form loss value should not be confused with the value of 1.56 used in the pressure flow approached adopted in [[1D_Bridges | TUFLOW 1D "B" and "BB" bridge]]. TUFLOW 1D bridge pressure flow approach is based on the section 4.13.2 "All Girders in Contact with Flow (Case II)" of ''Guide to Bridge Technology Part 8: Hydraulic Design of Waterway Structures'' (AUSTROADS, 2018). The original hydraulic experiment conducted by [https://hdl.handle.net/10217/39009 Liu et al (1957)] in a laboratory flume with a pair of bridge abutments and a deck. The flow conditions were similar to orifice flow due to the high blockage ratio caused by the abutments and the deck. When modelling bridges in 2D, the contraction/expansion losses caused by the abutments would be handled explicitly by the 2D solver, so a value 1.56 can lead to duplication of the contraction/expansion losses caused by the bridge abutments. 
 

=TUFLOW 2D Bridge Setup=
There are two methods available to model depth varying form loss of a bridge structure:
* [[TUFLOW_2D_Hydraulic_Structures#2D_Layered_Flow_Constriction_.282d_lfcsh.29 |2D Layered Flow Constriction (2d_lfcsh)]]
:The traditional method used to model depth-varying form loss through bridge components such as piers, decks, and rails.

*[[TUFLOW_2D_Hydraulic_Structures#2D_BG_Shape_.282d_bg.29 |2D BG Shape (2d_bg)]] (introduced in the 2023 release)
:A simplified approach developed to simplify the model input based on the findings from the joint TMR Study [https://tuflow.com/media/7554/2022-bridge-deck-afflux-modelling-benchmarking-of-cfd-and-swe-codes-to-real-world-data-collecutt-et-al-hwrs.pdf (Collecutt et al, 2022)].

Both methods provide options for representing flow surcharging, the pressure flow of bridge decks and eventually submerged bridge flow at higher water levels. During the surcharging of bridge decks, higher energy losses can be specified to simulate the pressure flow.

Examples for how to configure both approaches are provided in the 2D structures section of the [[TUFLOW_Example_Models#2D_Structures |TUFLOW Wiki Example Models]] and [[Tutorial_M04 |Tutorial Module 4]] - 2D Bridges.

==2D Layered Flow Constriction (2d_lfcsh)==
Four flow constriction layers are represented in a 2d_lfcsh layer. The lower three layers represents the pier, the bridge deck and the rails. Each layer has its own attributes to specify the blockage and the form loss coefficient. The top (fourth) layer assumes the flow is unimpeded, representative of flow over the top of a bridge. Within the same shape, the invert of the bed, and thickness of each layer can vary in 3D.

The following table provides an overview for how to determine the blockage and form loss coefficient for each layer: 
{| style="text-align: left; margin-left: 0; " class="wikitable" width="80%"
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Layer
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Description
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Blockage (%)
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Form Loss Coefficient (FLC)
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Notes
|-

| 1 || Pier layer || ~5% (can be omitted if included in FLC) || Estimate using [[TUFLOW_2D_Hydraulic_Structures#Pier_Losses | Pier Losses]] || Represents flow obstruction from piers beneath the bridge deck
|-
| 2 || Bridge deck || 100% || Use calibration data, if available, to determine FLC. If no calibration is available, estimate using [[TUFLOW_2D_Hydraulic_Structures#Bridge_Design_.28hB.2FT.29_vs_Form_Loss_Coefficient_Table | hB/T vs FLC]] table || Full blockage, no flow through the deck
If using the [[TUFLOW_2D_Hydraulic_Structures#Bridge_Design_.28hB.2FT.29_vs_Form_Loss_Coefficient_Table | hB/T vs FLC]] table, it is recommended to enable the Method C Form Loss Approach
|-
| 3 || Bridge rails || 10% – 100% || Use calibration data, if available, to determine FLC. 
If no calibration data is available, combined FLC for Layers 2 and 3 should be estimated using the [[TUFLOW_2D_Hydraulic_Structures#Bridge_Design_.28hB.2FT.29_vs_Form_Loss_Coefficient_Table | hB/T vs FLC]] table, where T = L2_Depth + (pBlockage × L3_Depth)
*(pBlockage × L3_Depth) represents the solid portion of the rails
*L2 FLC and L3 FLC should sum to the combined FLC
|Blockage and FLC depends on rail type Sensitivity testing with 100% blockage is recommended due to potential for debris during flood
If using the [[TUFLOW_2D_Hydraulic_Structures#Bridge_Design_.28hB.2FT.29_vs_Form_Loss_Coefficient_Table | hB/T vs FLC]] table, it is recommended to enable the Method C Form Loss Approach
|-
| 4 || Above rails || 0% || 0 || Represents unimpeded overtopping flow
|}
<ol>
[[File:2d_lfcsh_attributes.png | 500px ]]
</ol>
 

===Blockage===

The 2d_lfcsh functions by adjusting the flow width and the form loss of 2D cell faces. The combined blockage across the 4 layers is calculated at each simulation timesteps:
<ol>
 
[[File: Blockage_total_equation_01.png|600px]]
 
where 
'''''yi''''' is the actual depth of water in layer '''''i''''' 
'''''ytotal''''' is the total water depth 
</ol>

===Form Loss Approach===

The combined form loss coefficient is determined using one of three methods. The form loss coefficient method can be specified either individually using the 2d_lfcsh “Shape_Options” attribute or globally using the .tcf command: 
<tt>Layered FLC Default Approach == [ METHOD A | {METHOD B} | METHOD C | METHOD D]</tt> 

:METHOD A: The losses are accumulated as the water level rises through the layers. 
<ol>
[[File:Eq_flc_cumulate.png |450px]]
</ol>
:*Layer 1: Constant form loss (L1_FLC)
:*Layers 2 & 3: Form loss increases based on the depth of water in layer 2 & 3; peak form loss at top of Layer 3
:*Above Layer 3: Applies the full accumulated form loss continuously, even when overtopping begins (no reduction)
:Note: Simpler method but tends to overestimate losses when the structure is submerged or overtopped 

:METHOD B (default): the losses are applied pro-rata according to the depth of water in each layer. 
<ol>
[[File:Eq_flc_portion.png |430px]]
</ol>
:*Layer 1: Constant form loss (L1_FLC)
:*Layers 2 & 3: Form loss increases based on the depth of water in layer 2 & 3; peak form loss at top of Layer 3
:*Above Layer 3: Total form loss gradually reduces as water overtops the structure
:Note: Maintains backward compatibility but may underrepresent losses during pressurised or overtopped flows 

:METHOD C (recommended): hybrid approach combining Method A and Method B. 
<ol>
[[File:Eq_flc_methodC.png |520px]]
</ol>
:*Layer 1: Constant form loss (L1_FLC)
:*Layers 2 & 3: Gradual increase in form loss with water level, following Method A
:*Above Layer 3: Total form loss gradually reduces as water overtops the structure, following Method B
:Note: Recommended method; aligns closest to CFD modelling results and TUFLOW HPC behaviour.

:METHOD D: Allows the modeller to control the depth at which the losses start to reduce when the flow transitions between pressure flow and drowned flow.
:This approach is the same used by the 2d_bg layer (introduced in the 2023-03 release). It is recommended to use the 2d_bg layer as it has the benefit of a simplified attribute table, for easier user input.

===Form Loss Calibration Example - Iowa River Flood Study===

In this study, a combined form loss coefficient of 0.35 was used to match observed head loss during slight overtopping of a bridge. The FLC values for each layer were adjusted to achieve the correct combined form loss. The table and plot show how each layer contributes to the total form loss and highlight the differences in calculated form loss between the three methods.

{| style="text-align: left; margin-left: 0;" class="wikitable" width="60%"
!colspan="1" rowspan="2" style="background-color:#005581; font-weight:bold; color:white;" width=6%| Layer
!colspan="1" rowspan="2" style="background-color:#005581; font-weight:bold; color:white;" width=10%| Depth (m)
!colspan="1" rowspan="2" style="background-color:#005581; font-weight:bold; color:white;" width=12%| Blockage (%)
!colspan="2" style="background-color:#005581; font-weight:bold; color:white;" width=20%| Method A
!colspan="2" style="background-color:#005581; font-weight:bold; color:white;" width=20%| Method B
!colspan="2" style="background-color:#005581; font-weight:bold; color:white;" width=20%| Method C
|-
! style="background-color:#005581; font-weight:bold; color:white;"| Layer FLC
! style="background-color:#005581; font-weight:bold; color:white;"| Combined FLC
! style="background-color:#005581; font-weight:bold; color:white;"| Layer FLC
! style="background-color:#005581; font-weight:bold; color:white;"| Combined FLC
! style="background-color:#005581; font-weight:bold; color:white;"| Layer FLC
! style="background-color:#005581; font-weight:bold; color:white;"| Combined FLC
|-
| 1 || 5.0 || 5 || 0.07 || 0.07 || 0.07 || 0.07 || 0.07 || 0.07
|-
| 2 || 1.5 || 100 || 0.15 || 0.22 || 1.05 || 0.30 || 0.15 || 0.22
|-
| 3 || 1.0 || 50 || 0.13 || 0.35 || 0.70 || 0.35 || 0.13 || 0.35
|}

</ol>
 
<ol>
[[File:FLC_vs_height_updated.png | 600px ]]
</ol>

==2D BG Shape (2d_bg)==
2D BG Shape is similar to the Layered Flow Constriction, but has several updates to simplify the input based on the findings from the joint study with TMR [https://tuflow.com/media/7554/2022-bridge-deck-afflux-modelling-benchmarking-of-cfd-and-swe-codes-to-real-world-data-collecutt-et-al-hwrs.pdf (Collecutt et al, 2022)].

The following table provides an overview of how to determine the blockage and form loss coefficient for each layer: 
{| style="text-align: left; margin-left: 0; " class="wikitable" width="80%"
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Layer
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Description
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Blockage (%)
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Form Loss Coefficient (FLC)
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Notes
|-

| 1 || Pier layer || ~5% (can be omitted if included in FLC) || Estimate using [[TUFLOW_2D_Hydraulic_Structures#Pier_Losses | Pier Losses]] || Represents flow obstruction from piers beneath the bridge deck
|-
| 2 || Bridge deck || 100% || rowspan="2" | The Super Structure (Super_S) is the bridge deck and rails layers combined. 
Use calibration data, if available, to determine FLC. 
If no calibration data is available, the Super_S FLC should be estimated using the [[TUFLOW_2D_Hydraulic_Structures#Bridge_Design_.28hB.2FT.29_vs_Form_Loss_Coefficient_Table | hB/T vs FLC]] table, where T = Deck_Depth + (Rail_pBlockage*Rail_Depth)
*(Rail_pBlockage*Rail_Depth) represents the solid portion of the rails
|| Full blockage, no flow through the deck
|-
| 3 || Bridge rails || 10% – 100% || Sensitivity testing with 100% blockage is recommended due to potential for debris during flood events
|-
| 4 || Above rails || 0% || 0 || Represents unimpeded overtopping flow
|}

<ol>
[[File:2d_bg_attributes.png | 700px ]]
</ol>

===Inflection Point===

Based on findings from the joint study [https://tuflow.com/media/7554/2022-bridge-deck-afflux-modelling-benchmarking-of-cfd-and-swe-codes-to-real-world-data-collecutt-et-al-hwrs.pdf (Collecutt et al, 2022)], the head loss peaks when the water level is approximately 1.6*T above the bridge soffit, and decays slowly as the bridge becomes progressively drowned out. The 'SuperS_IPf' attribute (inflection point factor, default = 1.6) can be used to define the height of the inflection point. The solid portion of the rail layer is also added to the deck thickness to calculate the depth to the inflection point (DIP), i.e.:
<ol>
[[File:eq_flc_bg_infection_point.png | 520px ]]
</ol>

===Form Loss Approach===
The form loss approach is similar to the FLC approach METHOD C, with L2/L3 replaced by a single super structure layer:
<ol>
[[File:eq_flc_bg.png | 480px ]]
</ol>

===Form Loss Calibration Example - Iowa River Flood Study===
This example uses the same bridge setup described in the[[TUFLOW_2D_Hydraulic_Structures#Form_Loss_Calibration_Example_-_Iowa_River_Flood_Study | 2D Layered Flow Constriction]] section, with the following parameters applied:
*SuperS_FLC = 0.28
*SuperS_Ipf = 1.6,
The Depth to Inflection Point (DIP) is calculated as 3.2m above the bridge soffit.

The table and figure below show how the form loss value varies with water depth.
<ol>
{| style="text-align: center;" class="wikitable" width="32%"
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;" width=8%| Layer
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;" width=8%| Depth (m)
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;" width=8%| Blockage (%)
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;" width=8%| Form Loss
|-
| Pier || 5.0 || 5 || 0.07
|-
| Deck || 1.5 || 100 || rowspan="2" | 0.28
|-
| Rail || 1.0 || 50
|}

[[File:FLC_vs_height_bg.png | 600px ]]
</ol>

== 2D Bridges Line vs Polygon Layer ==
The form loss coefficient (FLC) is applied differently when using a line compared to a polygon for both 2d_lfcsh and 2d_bg inputs. The FLC is applied at cell sides (u and v faces) as this is where velocities are calculated. 
For larger bridges that spread across multiple cells, it is recommended to use a polygon layer, which selects all u and v faces falling within the polygon.
 
 
'''2D Layered Flow Constriction (2d_lfcsh)'''
{| style="text-align: left; margin-left: 0;" class="wikitable" width="80%"
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 7.5%;"| Geometry
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 7.5%;"| Line Type
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 11%;"| Width Attribute
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 22%;"| FLC Input
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 22%;"| FLC Applied
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 30%;"| Notes
|-
!rowspan="3" | Line
| Thin
| zero
| Total form loss of the bridge
| Applies the FLC to a single row of cell sides
| This approach is cell size independent. It is the easiest setup and the preferred / recommended approach when using 2d_lfcsh.
|-
| Thick
| between zero and 1.5 times the cell size
| Total form loss of the bridge
| FLC/2 applied to all sides of the selected cells
| A cell is selected if the polyline intersects the cell crosshair. Caution should be taken when using a "thick" line, as changes in cell size can cause it to become a "wide" line. If this occurs, the FLC attribute may need to be recalculated to avoid overestimating or underestimating losses.
|-
| Wide
| larger than 1.5 times the cell size
| Total form loss of the bridge ''(may need to be recalculated, see notes)''
| FLC divided by number of cell sides in the direction of flow 
''(number of cell sides in the direction of flow is calculated as line width divided by cell size)''
| Polygon shapes are recommended if more than 3 rows of faces must be selected.. 
Caution should be taken when using a "wide" line. The cell size and alignment of the 2d_lfcsh line may result in selecting too many or too few cell faces in the direction of the flow. The FLC input may need to be recalculated to ensure FLC Applied multiplied by the number of cell sides in the direction of flow equates to the intended total form loss.
|-
!rowspan="1" | Polygon
| -
| -
| Total loss per unit length (meters or feet) in the direction of flow
| FLC * cell size applied to all sides of selected cells
|
|}

'''2D Bridge (2d_bg)'''
{| style="text-align: left; margin-left: 0;" class="wikitable" width="80%"
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 7.5%;"| Geometry
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 7.5%;"| Line Type
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 11%;"| Width Attribute
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 22%;"| FLC Input
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 22%;"| FLC Applied
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 30%;"| Notes
|-
!rowspan="3" | Line
| Thin
| zero
| Total form loss of the bridge
| Applies the FLC to a single row of cell sides.
| This approach is cell size independent.
|-
| Thick
| larger than zero
| Total form loss of the bridge
| FLC/2 applied to all sides of the selected cells
| This approach is cell size independent. A cell is selected if the polyline intersects the cell crosshair.
|-
| Wide
| Not supported
| –
| –
| BG polygon shapes are recommended if more than 3 rows of faces must be selected.
|-
!rowspan="1" |Polygon
| -
| ''(used to automatically distribute the total FLC to the selected faces)''
| Total form loss of the bridge
| FLC / Deck_Width * cell size applied to all sides of selected cells
| For bridges modelled using a 2d_bg polygon the relative ratio of the bridge width to the 2D cell size should be 4 or greater. For more information on this see [https://downloads.tuflow.com/Other/2d_bg_R_Bridge_Configuration_Advice_202503.pdf 2d_bg_R_Bridge_Configuration_Advice.pdf].
|}
 
The following diagrams demonstrate how the input FLC is applied for the four geometry options for 2d_lfcsh and 2d_bg layers: 
[[File:2dlfcsh 2dbg combined v2.png|1200px]]

It is good modelling practice to check the [[Check_Files_2d_lfcsh_uvpt | lfcsh_uvpt_check]] and [[Check Files 2d bg uvpt check | bg_uvpt_check]] files to confirm the number of faces selected and the FLC values assigned. It is also strongly recommended to undertake a sensitivity analysis on the applied form losses in the model to check if it makes any difference to the results and/or double check against other methods (hand calculations, other software, CFD modelling), especially if the bridge is near an area of interest. If calibration data is available, this should be used to guide the form loss value specification. 
 

= Common Questions Answered (FAQ)=
== What blockage values should I use for bridge guard rails? ==
The blockage of bridge guard rails can be anything from 100% blocked (solid concrete rails) to 10% blocked (very open rails). In addition, the accumulation of debris during a flood can be substantial as shown in the image below. Sensitivity testing with 100% blockage is recommended.
 
[[File:Bridge rail debris.jpg | 500px]]

== How to conduct sensitivity test for 2D bridges? ==
General recommendations to cross-check the results are:
* Compare computed affluxes against desktop methods (e.g. Hydraulics of Bridge Waterways, 1978) and/or other software including CFD, especially for unusual bridge designs.
* Use any recorded flood marks or general observations from past events to check and calibrate FLC values.
* Conduct sensitivity testing by assessing the impact and influence of FLC values on your modelling objectives. The afflux resulting from the FLC values will be proportional to the velocity head, i.e. ∆h=FLC*(v^2/2g). As such, if velocities are low (e.g. 1 m/s), the results may not be overly sensitive to uncertainties in the FLC values. If completing a check using this equation for a long skew bridge it is best to calculate the total structure velocity from a PO line digitised in the same location as the bridge.

Finally, after completing sensitivity testing and understanding the range of uncertainty due to unknowns like the degree of blockage and influence of FLC values (e.g. +/-20%), you are in a position to discuss with your client how best to proceed. For example, if the modelling is to set planning levels for a development upstream then it may be appropriate to choose values on the higher side (higher FLC values and/or blockage assumptions), noting that the uncertainty may be amply covered by a regulatory freeboard. Conversely, if the development is on the downstream side the conservative approach would be to use the results at the lower end of your FLC/blockage values. 
[[File:Bridge Flood Debris Loading.jpg | 500px]] 

== Should I use both FLC and blockage for layer one in 2D bridge layered flow constriction? ==
When applying FLC and blockage values to model obstructions such as piers, the following considerations need to be taken into account:
* The FLC value applies an energy loss along 1D channels or across 2D cell faces equivalent to FLC*V2/2g where V is the 1D channel velocity or the 2D cell face velocity.
* FLC values are often sourced from publications such as Hydraulics of Bridge Waterways or AustRoads (e.g. Kp chart for piers).
* If possible, establish whether the source of the FLC value is based on the approach velocity (the velocity in the absence of piers) or structure velocity (the velocity with area blocked out by the piers) noting that it often isn’t clear or stated.
** If it is the structure velocity, this is usually the velocity at the vena-contracta (point of greatest contraction within the entrance to the structure and therefore highest velocity) - see image below. Bluff or sharp-edged obstructions will have a much more pronounced vena-contracta, and therefore higher velocity compared with a round-edged obstruction.
** FLC values based on the approach velocity will be higher than those based on the structure velocity to achieve the same energy loss.
* Applying a blockage equivalent to the obstruction width will increase, usually very slightly, the velocity of the 1D channel or 2D cell face. This won’t be the vena-contracta velocity, but a velocity between the approach velocity and the vena-contracta velocity. A greater blockage will need to be applied to emulate the vena-contracta velocity.
* If the FLC source value is based on:
** The approach velocity then there is no need to apply a blockage value.
** The structure velocity then the blockage value should be applied noting that it may be appropriate to apply a larger blockage to take into account the vena-contracta.
* If it is not clear or unknown whether the FLC source value is based on the approach or structure velocity, the recommendation would be to apply the blockage in the interests of being slightly conservative on the upstream flood level calculation.
* For most minor obstructions such as bridge piers, the blockage is usually relatively small and whether included or not has a negligible or minor affect on flood levels compared with other factors such as the approach embankments and the bridge deck.
* Blockage from debris wrapped around piers can have a greater influence on the results than the effect of applying or not applying a blockage. Debris wrapped around piers can be accounted for in the FLC value calculated for the pier layer.
* As always, sensitivity testing with and without blockage and +/- the FLC value is highly recommended to understand their importance in regard to the broader modelling objectives and the effects of uncertainties in the input data, boundaries, other parameters such as Manning’s n values, and the accuracy of the numerical solution scheme (see [https://www.tuflow.com/library/webinars/#maximise_accuracy Maximising the Accuracy of Hydraulic Models webinar]).
[[File: Vena_contracta.png]] 
''Image showing the formation of the vena-contracta.'' 
 

==I don't see results that I expect when using 2d_lfcsh layer==
The 2d_lfcsh layer is a versatile feature that was designed to model bridges in 2D, but can also be used for other applications like fences, buildings raised on pillars and so on.
Some of the unexpected results could be:
* Water level going through the bridge deck in 2D map output.
* Water transiting through 100% blocked Layer 1, e.g. fences with solid base.
* SHMax.csv reporting values above the bridge deck when 2D map output reports water level lower than the top of the bridge deck.

TUFLOW is a 2D solution (not 3D), in the 2d_lfcsh layer the percent blockage and form loss coefficient applied to the cell faces is depth averaged across the entire cell face (across Layer 1, 2 and 3): 
*For bridges, where Layer 2 has a 100% blockage applied, the minimum flow width of 0.001m is used and is averaged with the Layer 1 blockage (based on the depth of the water). This may result in a water level being reported within or above the bridge deck, which would represent the pressure head.
*Layered flow constriction works by adjusting the flow area of the cell faces by any blockages to generate the correct depth averaged velocity at each face at which the form losses are applied as a fraction of the V2/2g kinetic energy. Calculating the correct velocity is critical for determining the losses as the losses are proportional to the velocity squared. 
*For a layered flow constriction cell face the flow area cannot be zero above the invert of Layer 1 to avoid a divide by zero in the computations, therefore a minimum average flow width after applying blockages of 0.001 m is applied. if Layer 1 is 100% blocked, a very small amount of water will flow through Layer 1. If this is unacceptable, instead of applying 100% blockage of Layer 1, the preferred approach is to start the layered flow constriction at the top of Layer 1 or raise the ground elevation to the top of Layer 1 using one of the Z Shape modification functions (e.g. a breakline). 
<ol>
[[File:100% Blockage Diagram.png | 500px]]
</ol>

== Can I model bridge piers explicitly in 2D using very small cells? ==
It isn't recommended to explicitly model bridge piers by blocking out the pier faces in TUFLOW, or in any hydraulic modelling software based on solving Shallow Water Equations(SWE). Due to the 3-dimentiality of the flow and turbulence around a pier, computational fluid dynamics (CFD) approach is often required to simulate the flow around piers explicitly. The wake turbulence behind a simple-shape pier can be resolved to some extent using extremely fine mesh in TUFLOW (see calibration example to a flume experiment in the [https://www.tuflow.com/library/webinars/#structures webinar on Energy Losses at Structures]), however the predictions for head losses show notable sensitivities to the mesh size, the mesh design, and the choice of turbulence model. The extremely fine mesh resolution also results in significantly higher computational costs.

Therefore, the safest and strongly recommended approach with regard to establishing head losses and consequently flood levels, is to model the effects of such obstructions with form loss coefficients (applied to selected mesh cells) that have been derived from physical testing. This approach has been shown to provide the most consistent results across various mesh resolutions. It also has the added benefit that, by avoiding small cells in the mesh, it will provide much more efficient run times for flow solvers.

[[File:Flow round a cylinder.png]]

''The point of flow separation around an object has a major bearing on the drag coefficient and is not reliably reproduced by 2D or 3D software.''


== How to best convert flow constriction data (2d_fc or 2d_fcsh) into newer formats (2d_lfcsh or 2d_bg)? ==
The form loss parameters can be transferred from the flow constriction (2d_fc or 2d_fcsh) to the first layer of the layered flow constriction (2d_lfcsh) or pier layer of the 2d_bg. Definition of the remaining form loss and blockage layer inputs should follow the guidance outlined in [[TUFLOW_2D_Hydraulic_Structures#2D_Layered_Flow_Constriction_.282d_lfcsh.29 | 2D Layered Flow Constriction]] and [[TUFLOW_2D_Hydraulic_Structures#2D_BG_Shape_.282d_bg.29 | 2D BG Shape]] paragraphs. 
When using floating pontoon (type FD in the 2d_fc or 2d_fcsh) different setup might need to be used for different events. For large events when floating pontoon becomes fixed at the top of the supporting piles, standard 2d_lfcsh setup can be used. Smaller events when the pontoon is floating at different heights might require more sensitivity testing of the structure parameters to find out a setup the matches the reality as close as possible. 

== Should I model bridges in 1D or 2D Domain? ==
The recommended approach typically depends on the study objectives and if the channel upstream and downstream of the bridge is modelled in 1D or 2D. To preserve the momentum as accurately as possible the bridge should be modelled in the same dimension as the channel, e.g. 1d_nwk bridge if the channels is in 1D and 2d_bg or 2d_lfcsh if the channel is modelled in 2D. 
In 2D, the expansion/contraction losses are modelled based on the topography and don't need to be estimated as attributes as for 1D modelling. Also, for higher flows where the bridge is overtopped, 2D is preferable approach.

== What is the difference between downstream and upstream controlled flow? ==
Downstream control means a change in downstream water level will cause a change in upstream water level. Upstream control means the upstream water level is insensitive to the downstream water level and usually indicates the occurrence of supercritical flow.

== What FLC values should be used for 2d_bg bridge if hB/T is below 2 or above 6? ==
TMR has extended the CFD simulation to hB/T ratios of 1 to 10. Refer to the [https://docs.tuflow.com/classic-hpc/manual/latest/ TUFLOW Manual] for details.

If hB/T is outside this ratio:
* hB/T ratios of less than 1 represent a very unusual bridge sitting low to the ground, and the peak FLC may increase above the end value (FLC of 0.6) in a way that doesn't follow the research trend or extrapolation. For these cases we would recommend using CFD modelling to obtain a more informed value. Alternatively, computing an FLC based on pressure flow or using 1D culvert might be considered.
* For hB/T ratios of greater than 10, the FLC is likely to continue to decrease, but probably not significantly. Clamping to the end value (FLC of 0.16) might be considered the more conservative approach (if the primary concern is flood levels upstream of the bridge). 
 
{{Tips Navigation
|uplink=[[ TUFLOW_Modelling_Guidance | Back to TUFLOW Modelling Guidance]]
}}

File:Incremental backwater coefficient 2018 pier losses.png

2026-04-08T05:47:21Z

Emilie Nielsen:

TUFLOW BC Advice

2026-04-08T05:35:07Z

Emilie Nielsen: /* I wish to use a PO line to monitor the flow exiting a model. Should I snap the PO line to the downstream boundary for this purpose? */

The following links provide useful boundary condition guidance to TUFLOW users.

* [[TS1_File_Format | TS1 File Format]]
* [[TUFLOW_NetCDF_Rainfall_Format|TUFLOW NetCDF Rainfall Format]]
* [[TUFLOW_Rainfall_Control_File_Examples | TUFLOW Rainfall Control File Examples]]
* [[TUFLOW_2D2D_BC_Advice| Multiple Domain 2D/2D Boundary Configuration Guidance]]
* [[TUFLOW_1D2D_Boundary_Configuration_Guidance| 1D/2D Boundary Configuration Guidance (SX and HX)]]
=Frequently Asked Questions (FAQ)=
==I wish to use a PO line to monitor the flow exiting a model. Should I snap the PO line to the downstream boundary for this purpose?==
Plot Output (PO) Q lines report model flow results for water crossing the digitised line. Computationally, TUFLOW transposes the digitised PO line to the closest adjacent cell face for the output calculation. In addition to this, TUFLOW requires an active 2D cell on either side (upstream and downstream) of the cell face for the calculation. Collectively, these requirements are necessary for accurate flow calculations irrespective of the orientation of the PO line relative to the cell alignment. 
It is best practice to snap 2D boundary condition lines, such as HT, QT and HQ, to the extent of the 2D code active area polygon at an orientation roughly perpendicular to the expected flow direction. This model design requirement means the 2D boundary condition lines are located along the outermost 2D cells in a model. Snapping a 2D PO line to the 2D boundary condition may align segments of the Plot Output (PO) Q result inspection line along the outermost cell faces of the model. This does not comply with TUFLOW’s requirement for an active 2D cell on either side of the Plot Output (PO) Q result inspection line. As a result, snapping a 2D PO line to the 2D boundary condition line may underestimate the flow exiting a model. For this reason, Plot Output (PO) Q lines should NOT be snapped to 2D boundary condition lines. The PO line should be defined immediately upstream of the downstream boundary. Use the [[Check_Files_2d_PO|po_check]] and [[Check_Files_2d_grd|grd_check]] files to review the PO line location to ensure there are active cells each side of the PO line.

The image below shows a downstream 2d_bc boundary condition line (HQ) in purple, snapped to the edge of the 2d_code polygon. A 2d_po line (blue arrow) has been digitised just upstream of the boundary. The [[Check_Files_2d_PO|po_check]] and [[Check_Files_2d_grd|grd_check]] files have been loaded in to confirm that there is an active 2D cell on either side of the 2d_po line. 
 
[[File:BC_advice_01.png]]

== Can TUFLOW model a waterfall? ==
Yes, TUFLOW can model waterfalls, but it requires careful handling of supercritical flow conditions.

As water approaches a waterfall, it speeds up and transitions into free fall. To ensure realistic behaviour, the model must allow for this acceleration rather than imposing an artificial depth at the brink.

Here are three suggested approaches in TUFLOW:

# '''HQ (Water Level versus Flow) Boundary:''' Defining a custom HQ curve ensures the model correctly represents the flow acceleration before the waterfall.
# '''Steep Slope HQ Boundary:''' Setting a higher slope value in the automatic HQ boundary can also generate supercritical conditions near the outlet.
# '''2D HPC Weir:''' Modelling a small drop in 2D cell elevations with a weir structure can better reflect natural waterfall hydraulics.

It is also recommended to run sensitivity tests with different boundary setups to check how the downstream conditions influence the model results.{{Tips Navigation
|uplink=[[ TUFLOW_Modelling_Guidance | Back to TUFLOW Modelling Guidance]]
}}

File:BC advice 01.png

2026-04-08T05:34:30Z

Emilie Nielsen:

TUFLOW Example Models

2026-04-08T05:05:49Z

Emilie Nielsen: /* Example Model Catalogue */

=Introduction=
These example models have been developed to demonstrate the most common TUFLOW model design features and applications. This dataset is useful for experienced modellers wishing to further develop their skills via demonstration examples. Although the models are based on the TUFLOW tutorial model dataset, new users are encouraged to familiarise themselves with TUFLOW through the [[Tutorial_Introduction |Tutorial Model Introduction]] before using this dataset. Unlike the tutorials, this dataset does not include step-by-step instructions / documentation. Users of this dataset are expected to have a basic knowledge TUFLOW, and have suitable skills to open the model files by referencing the TUFLOW Control File (TCF) referenced in the feature catalogue list below. 

=Example Model Data=
The model data is available for download from https://downloads.tuflow.com/TUFLOW/Wiki_Example_Models/TUFLOW_Example_Model_Dataset.zip 
The dataset only includes model input files. The models can be run to create simulation check and result files. Batch files (*.bat) for each of the example feature categories has been provided within the "runs" folder of the TUFLOW project. 

If you are unfamiliar with using batch files, additional information explaining how to use them to execute multiple simulations is available here: [[Run_TUFLOW_From_a_Batch-file| Run TUFLOW From a Batch-file]].

=Example Model Catalogue=
Below is a complete list of the example models. This dataset uses TUFLOW HPC as the computational engine.

Click on the following shortcuts to skip directly to the targeted major feature category in the table below: 
*[[TUFLOW_Example_Models#Project Initiation| Project Initiation]]
*[[TUFLOW_Example_Models#Model Units| Model Units]]
*[[TUFLOW_Example_Models#Solver Options| Solver Options]]
*[[TUFLOW_Example_Models#Output Options| Output Options]]
*[[TUFLOW_Example_Models#Boundary Condition Options| Boundary Condition Options]] (Inflows, Outflows, Losses)
*[[TUFLOW_Example_Models#Topography Features| Topography Features]] (Static Updates, Dynamic Updates, Sub-Grid Sampling)
*[[TUFLOW_Example_Models#Structures| Structures]] (Bridges, Weirs, Culverts, Operational Controls)
*[[TUFLOW_Example_Models#Multiple Domain Model Design| Multiple Domain Model Design]] (2D/2D Quadtree, 1D open channel / 2D floodplain, 1D pipe network / 2D floodplain)
*[[TUFLOW_Example_Models#Bulk Simulation Management| Bulk Simulation Management]]
*[[TUFLOW_Example_Models#Advection Dispersion| Advection Dispersion]]
*[[TUFLOW_Example_Models#Non-Newtonian | Non-Newtonian]]
*[[TUFLOW_Example_Models#Mathematical Operations| Mathematical Operations]]

{| class="wikitable" style="text-align:center;"
! colspan="4" style="position:sticky; top:0; background-color:#005581; font-weight:bold; color:white; z-index:2;" | Example Model Catalogue
|-
! colspan="2" style="position:sticky; top:2.2em; background-color:#fff; font-weight:bold; z-index:2;" | Model Category
! style="position:sticky; top:2.2em; background-color:#fff; font-weight:bold; z-index:2;" | Description
! style="position:sticky; top:2.2em; background-color:#fff; font-weight:bold; z-index:2;" | Model Name
|-
| colspan="2" id="Project Initiation" | Project Initiation
| Write empty files
| Create_Empties.tcf
|-

|-
| colspan="2" rowspan="2" id="Model Units" |Model Units
|Basic 2D model (SI units - m)
|EG00_001.tcf
|-
|Basic 2D model (US units - ft)
|EG00_002.tcf
|-

|-
| colspan="2" rowspan="8" id="Solver Options" |Solver Options
|TUFLOW Classic
|Refer to [[TUFLOW_Classic_Example_Model_Archive| TUFLOW Classic Example Model Archive]]
|-
|TUFLOW HPC - Sub-Grid Sampled (SGS) topography enabled
|EG01_002.tcf
|-
|TUFLOW HPC - Sub-Grid Sampled (SGS) topography disabled
|EG01_003.tcf
|-
|TUFLOW HPC - Multiple GPU cards
|EG01_004.tcf
|-
|TUFLOW HPC - Newtonian Viscosity (Wu Turbulence)
|EG01_006.tcf
|-
|TUFLOW HPC - Newtonian Viscosity (Smagorinsky)
|EG01_007.tcf
|-
|TUFLOW HPC - Quadtree
|See Section [[TUFLOW_Example_Models#Multiple Domain Model Design| EG13]]
|-
|ESTRY
|See Section [[TUFLOW_Example_Models#1D Culverts, Bridges, Weirs| EG11]], [[TUFLOW_Example_Models#1D Operating Structures| EG12]], [[TUFLOW_Example_Models#1D Pipe Network / 2D Floodplain Modelling| EG15]]
|-

| colspan="2" rowspan="19" id="Output Options" |Output Options
|2D xmdf (binary time series) and grid (maximums) output
|EG02_001.tcf
|-
|Time and duration of inundation (Time Output Cut-off = Depth)
|EG02_002.tcf
|-
|Time and duration of inundation (Time Output Cut-off = VxD)
|EG02_003.tcf
|-
|Time and duration of inundation (Time Output Cut-off = Hazard)
|EG02_004.tcf
|-
|Gauge level map output interval control (2d_glo)
|EG02_005.tcf
|-
|2D SGS high resolution grid output
|EG02_006.tcf
|-
|2D SGS high resolution grid output with manual specification of output resolution
|EG02_007.tcf
|-
|Output Zone (2d_oz)
|EG02_008.tcf
|-
|Write Restart File (See EG06_004.tcf for Read Restart File)
|EG02_009.tcf
|-
|2D plot output (2d_po point, line and region)
|EG02_010.tcf
|-
|2D structure outputs
|EG02_011.tcf
|-
|2D Long Profile (2d_lp)
|EG02_012.tcf
|-
|1D/2D Reporting locations - 1D river (1d_nwk), 2D floodplain
|EG02_013.tcf
|-
|1D/2D Reporting locations - 1D pipe network (1d_nwk), 2D floodplain
|EG02_014.tcf
|-
|Evacuation route inundation reporting (2d_zshr) (Route Cut Off Type = Depth)
|EG02_015.tcf
|-
|Evacuation route inundation reporting (2d_zshr) (Route Cut Off Type = Velocity)
|EG02_016.tcf
|-
|Evacuation route inundation reporting (2d_zshr) (Route Cut Off Type = VxD)
|EG02_017.tcf
|-
|Evacuation route inundation reporting (2d_zshr) (Route Cut Off Type = Hazard)
|EG02_018.tcf
|-
|Translating gauge data information to catchment receptors (Read GIS Objects)
|EG02_019.tcf

|-
| rowspan="52" id="Boundary Condition Options" |Boundary Condition Options
| rowspan="19" id="Inflows" |Inflows
|2D flow (m^3/s) vs time upstream inflow (2d_bc, QT)
|EG03_001.tcf
|-
|2D head (m) vs time upstream inflow (2d_bc, HT)
|EG03_002.tcf
|-
|Internal catchment inflow (m^3/s)(2d_sa)
|EG03_003.tcf
|-
|Internal catchment inflow (m^3/s) with streamlines (2d_sa, 2d_strm)
|EG03_004.tcf
|-
|Internal catchment rainfall (mm) (2d_sa_rf)
|EG03_005.tcf
|-
|Direct rainfall (mm) (2D Global Rainfall)
|EG03_006.tcf
|-
|Direct rainfall (mm) (2d_rf)
|EG03_007.tcf
|-
|Direct rainfall (mm) (Rainfall Control File - IDW)
|EG03_008.tcf
|-
|Direct rainfall (mm) (Rainfall Control File - TIN)
|EG03_009.tcf
|-
|Direct rainfall (mm) (Rainfall Control File - Poly)
|EG03_010.tcf
|-
|Direct rainfall (mm) (time varying gridded rainfall) - netcdf format
|EG03_011.tcf
|-
|Direct rainfall (mm) (time varying gridded rainfall) - flt format
|EG03_012.tcf
|-
|Direct rainfall (mm) (2d_rf) - negative rainfall
|EG03_013.tcf
|-
|Direct rainfall (2d_rf) and internal catchment rainfall (2d_sa_rf) for buildings
|EG03_014.tcf
|-
|HEC-DSS flow (m^3/s) vs time upstream inflow (2d_bc, QT)
|EG03_015.tcf
|-
|HEC-DSS flow (m^3/s) vs time upstream inflow (2d_bc, QT, multiple events)
|EG03_016.tcf
|-
|1D flow (m^3/s) vs time upstream inflow (1d_bc, QT)
|EG14_001.tcf
|-
|1D flow (m^3/s) vs time internal inflow (1d_bc, QT)
|EG14_002.tcf
|-
|1D flow (m^3/s) vs time internal inflow to 1D pits (1d_bc, QT)
|EG14_003.tcf
|-

| rowspan="6" id="Outflows" |Outflows
|2D Automatic stage discharge downstream boundary (2d_bc, HQ)
|EG04_001.tcf
|-
|2D User-specified stage discharge downstream boundary (2d_bc, HQ)
|EG04_002.tcf
|-
|2D Stage time downstream boundary (2d_bc, HT)
|EG04_003.tcf
|-
|1D Automatic stage discharge downstream boundary (1d_bc, HQ)
|EG04_004.tcf
|-
|1D User-specified stage discharge downstream boundary (1d_bc, HQ)
|EG04_005.tcf
|-
|1D Stage time downstream boundary (1d_bc, HT)
|EG04_006.tcf
|-

| rowspan="19" id="Loss Options" |Loss Options
|Rainfall excess loss approach - IL/CL (Global loss applied via the TBC file)
|EG05_001.tcf
|-
|Rainfall excess loss approach - IL/CL (applied via the materials file)
|EG05_002.tcf
|-
|Infiltration loss approach - IL/CL
|EG05_003.tcf
|-
|Infiltration loss approach - IL/CL, porosity
|EG05_004.tcf
|-
|Infiltration loss approach - IL/CL, porosity, initial moisture
|EG05_005.tcf
|-
|Infiltration loss approach - Green Ampt (USDA soil type)
|EG05_006.tcf
|-
|Infiltration loss approach - Green Ampt (USDA soil type), initial moisture
|EG05_007.tcf
|-
|Infiltration loss approach - Green Ampt (USDA soil type), initial moisture, ponding
|EG05_008.tcf
|-
|Infiltration loss approach - Green Ampt (User specified soil properties)
|EG05_009.tcf
|-
|Infiltration loss approach - Green Ampt (User specified soil properties), initial moisture
|EG05_010.tcf
|-
|Infiltration loss approach - Green Ampt (User specified soil properties), initial moisture, ponding
|EG05_011.tcf
|-
|Infiltration loss approach - Horton
|EG05_012.tcf
|-
|Infiltration loss approach - Horton, porosity
|EG05_013.tcf
|-
|Infiltration loss approach - Horton, porosity, initial moisture
|EG05_014.tcf
|-
|Groundwater - no horizontal infiltration
|EG05_015.tcf
|-
|Groundwater - 1 soil layer, horizontal hydraulic conductivity
|EG05_016.tcf
|-
|Groundwater - 2 soil layers, horizontal hydraulic conductivity
|EG05_017.tcf
|-
|Groundwater level versus time downstream boundary (2d_bc, GT)
|EG05_018.tcf
|-
|Groundwater linking to 1D
|EG05_019.tcf
|-

| rowspan="8" id="Other" |Other
|Spatially varied initial water level commands (2d_iwl)
|EG06_001.tcf
|-
|Spatially varied initial water level commands (Grid 2d_iwl)
|EG06_002.tcf
|-
|2D pump (2d_bc, SH)
|EG06_003.tcf
|-
|Read Restart File (See EG02_009.tcf for Write Restart File)
|EG06_004.tcf
|-
|Storage Reduction Factor (global specification)
|EG06_005.tcf
|-
|Storage Reduction Factor (2d_srf) (location specific update)
|EG06_006.tcf
|-
|External Stress - Wind (global specification)
|EG06_007.tcf
|-
|Dynamic Topography Options (Dam / Levee Failure)
|See Section [[TUFLOW_Example_Models#Dynamic Topography Updates| EG08]]

|-
| rowspan="28" id="Topography Features" |Topography Features
| rowspan="12" id="Static Topography Updates" |Static Topography Updates
|Cell resolution change
|EG07_001.tcf
|-
|Thin breakline topography update (2d_zsh_L, 2d_zsh_P)
|EG07_002.tcf
|-
|Thick breakline topography update (2d_zsh_L, 2d_zsh_P)
|EG07_003.tcf
|-
|Gully (Min) breakline topography update (2d_zsh_L, 2d_zsh_P)
|EG07_004.tcf
|-
|Ridge (Max) breakline topography update (2d_zsh_L, 2d_zsh_P)
|EG07_005.tcf
|-
|Region update - Absolute value change, No merge (2d_zsh_R)
|EG07_006.tcf
|-
|Region update - Relative value change, No merge (2d_zsh_R)
|EG07_007.tcf
|-
|Region update - Absolute value change, Partial merge (2d_zsh_R, 2d_zsh_P)
|EG07_008.tcf
|-
|Region update - Feature removal (2d_zsh_R)
|EG07_009.tcf
|-
|Advanced topography update - TIN (2d_ztin_R, 2d_ztin_P)
|EG07_010.tcf
|-
|Advanced topography update - TIN (2d_ztin_R, 2d_ztin_L, 2d_ztin_P)
|EG07_011.tcf
|-
|Depth varying Manning's n
|EG07_012.tcf
|-
| rowspan="13" id="Dynamic Topography Updates" |Dynamic Topography Options (Dam / Levee Failure)
|2D embankment failure - Time trigger, linear evolution
|EG08_001.tcf
|-
|2D embankment failure - Time trigger, non-linear evolution
|EG08_002.tcf
|-
|2D embankment failure - Water level trigger, linear evolution
|EG08_003.tcf
|-
|2D embankment failure - Water level trigger, non-linear evolution
|EG08_004.tcf
|-
|2D embankment failure - Water level difference trigger, linear evolution
|EG08_005.tcf
|-
|2D embankment failure - Water level difference trigger, non-linear evolution
|EG08_006.tcf
|-
|2D flood barrier reinstatement - Time trigger
|EG08_007.tcf
|-
|2D flood barrier reinstatement - Water level trigger
|EG08_008.tcf
|-
|2D flood barrier reinstatement - Water level difference trigger
|EG08_009.tcf
|-
|1D piping failure transitioning to 1D dam failure - Time trigger
|EG08_010.tcf
|-
|1D dam failure - Time trigger
|EG08_011.tcf
|-
|1D piping failure transitioning to 1D dam failure - Water level trigger
|EG08_012.tcf
|-
|1D dam failure - Water level trigger
|EG08_013.tcf
|-
| rowspan="3" id="Sub Grid Sampling" |Sub Grid Sampling
|Breakline detection delta tool
|EG09_001.tcf
|-
|2D SGS high resolution grid output
|EG09_002.tcf
|-
|2D SGS high resolution grid output with manual specification of output resolution
|EG09_003.tcf
|-
| rowspan="37" id="Structures" |Structures
| rowspan="9" id="2D Structures" |2D Structures
|Bridge (2d_fc)
|Refer to [[TUFLOW_Classic_Example_Model_Archive| TUFLOW Classic Example Model Archive]]
|-
|Bridge (2d_fcsh)
|Refer to [[TUFLOW_Classic_Example_Model_Archive| TUFLOW Classic Example Model Archive]]
|-
|Bridge - horizontal deck (2d_lfcsh)
|EG10_003.tcf
|-
|Bridge - variable deck form geometry (2d_lfcsh)
|EG10_004.tcf
|-
|Bridge - horizontal deck (2d_bg)
|EG10_005.tcf
|-
|2D weir coefficient change (global specification)
|EG10_006.tcf
|-
|2D weir coefficient change (location specific update)
|EG10_007.tcf
|-
|Bridge (2d_bg) - horizontal deck, auto superstructure FLC
|EG10_008.tcf
|-
|Fences (2d_lfcsh)
|EG10_009.tcf
|-

| rowspan="14" id="1D Structures" |1D Structures
|1D culverts - Circular and Box type. SX point, line and region 1D/2D examples
|EG11_001.tcf
|-
|1D culverts - Irregular shape (e.g. Arch)
|EG11_002.tcf
|-
|1D culverts - Unidirectional structures (flapgate) (1d_nwk)
|EG11_003.tcf
|-
|1D culverts - ARR2019 blockage matrix (1d_nwk)
|EG11_~e1~_~e2~_004.tcf
|-
|1D M channel - User defined flow matrix (1d_nwk)
|EG11_005.tcf
|-
|1D Q channel - Upstream Depth-Discharge Relationship (1d_nwk)
|EG11_006.tcf
|-
|Bridge (1d_nwk, 1d_bg)
|EG11_007.tcf
|-
|Weir (1d_nwk)
|EG11_008.tcf
|-
|Pump (1d_nwk) - pump curve
|EG11_009.tcf
|-
|Sluice gate (1d_nwk)
|EG11_010.tcf
|-
|Gated spillway (1d_nwk)
|EG11_011.tcf
|-
|Arch bridge (1D), no orifice flow
|EG11_012.tcf
|-
|Arch bridge (1D), orifice flow enabled
|EG11_013.tcf
|-
|Arch bridge (1D), orifice flow enabled with calibration factor
|EG11_014.tcf
|-

| rowspan="14" id="1D Operating Structures" |1D Operating Structures
|Pump operational (1d_nwk) - time trigger
|EG12_001.tcf
|-
|Pump operational - 1D water level trigger (1d_nwk)
|EG12_002.tcf
|-
|Pump operational - 2D water level trigger (1d_nwk)
|EG12_003.tcf
|-
|Pump operational - Depth above structure invert trigger (1d_nwk)
|EG12_004.tcf
|-
|Q flow matrix - Operation based on water level trigger (1d_nwk)
|EG12_005.tcf
|-
|Q flow matrix - Operation based on water level trigger and time delay (1d_nwk)
|EG12_006.tcf
|-
|Sluice gate operational - Time trigger (simulation time) (1d_nwk)
|EG12_007.tcf
|-
|Sluice gate operational - Water level trigger(1d_nwk)
|EG12_008.tcf
|-
|Gated spillway operational - Time trigger (Day) (1d_nwk)
|EG12_009.tcf
|-
|Gated spillway operational - Water level trigger (1d_nwk)
|EG12_010.tcf
|-
|Coordinated operation (multiple interacting structures) - Pump and Gated Spillway
|EG12_011.tcf
|-
|Coordinated operation controlled by status of another structure
|EG12_012.tcf
|-
|Pump operational (1d_nwk) - pump curve
|EG12_013.tcf
|-
|Pump operational (1d_nwk) - Time stamp after water level trigger
|EG12_014.tcf
|-

| rowspan="17" id="Multiple Domain Model Design" |Multiple Domain Model Design
| rowspan="5" id="2D/2D Modelling" |2D/2D Modelling
|TUFLOW HPC - Quadtree: Sample target distance
|EG13_001.tcf
|-
|TUFLOW HPC - Quadtree: Sample frequency nesting
|EG13_002.tcf
|-
|TUFLOW HPC - Quadtree: Memory efficient pre-processing
|EG13_003.tcf
|-
|TUFLOW HPC - Quadtree: Sample frequency
|EG13_004.tcf
|-
|TUFLOW Classic - M2D
|Refer to [[TUFLOW_Classic_Example_Model_Archive| TUFLOW Classic Example Model Archive]]
|-
| rowspan="1" id="1D Open Channel / 2D Floodplain Modelling" |1D Open Channel / 2D Floodplain Modelling
|1D river (1d_nwk), 2D floodplain
|EG14_001.tcf
|-

| rowspan="11" id="1D Pipe Network / 2D Floodplain Modelling" |1D Pipe Network / 2D Floodplain Modelling
|1D pipe network (1d_nwk), 2D floodplain, 2d_sa_rf inflow (mm) to 1D pits
|EG15_000.tcf
|-
|1D pipe network (1d_nwk), 2D floodplain, 2d_sa inflow (m^3/s) to 1D pits
|EG15_001.tcf
|-
|1D pipe network (1d_nwk), 2D floodplain, 2d_rf direct rainfall
|EG15_002.tcf
|-
|1D pipe network (1d_nwk), 2D / 2D floodplain quadtree
|EG15_003.tcf
|-
|1D pipe network (1d_nwk), manually specified manholes (1d_mh), 2D floodplain
|EG15_004.tcf
|-
|1D pipe network (1d_nwk), non-default (fixed) manhole loss method, 2D floodplain
|EG15_005.tcf
|-
|1D pipe network (1d_nwk), localised manually specified manhole losses, 2D floodplain
|EG15_006.tcf
|-
|1D virtual pipes, 2D floodplain
|EG15_007.tcf
|-
|1D virtual pipes connected to 1D pipe network (trunk drainage line), 2D floodplain
|EG15_008.tcf
|-
|1D storage tank (1d_na)
|EG15_009.tcf
|-
|1D storage tank (1d_nwk)
|EG15_010.tcf
|-

| rowspan="6" id="Bulk Simulation Management" |Bulk Simulation Management
| rowspan="6" id="Scenario / Event Management" |Scenario / Event Management
|Scenario (single)
|EG16_~s1~_001.tcf
|-
|Scenario (multiple)
|EG16_~s1~_~s2~_002.tcf
|-
|Set Variable
|EG16_~s1~_~s2~_003.tcf
|-
|Event (single)
|EG16_~e1~_004.tcf
|-
|Event (multiple)
|EG16_~e1~_~e2~_005.tcf
|-
|Scenario (multiple), Event (multiple), Set Variable
|EG16_~s1~_~s2~_~e1~_~e2~_006.tcf
|-

| rowspan="10" id="Other" |Other
| rowspan="3" id="Advection Dispersion" |Advection Dispersion
|Advection Dispersion
|EG17_001.tcf
|-
|Advection Dispersion with settling
|EG17_002.tcf
|-
|Advection Dispersion with decay
|EG17_003.tcf
|-
| rowspan="2" id="Non-Newtonian" |Non-Newtonian
|Non-newtonian viscosity
|EG18_001.tcf
|-
|Non-newtonian mixing (dam failure scenario)
|EG18_002.tcf
|-
| rowspan="5" id="Mathematical Operations" |Mathematical Operations
|Unit Conversion
|EG19_001.tcf
|-
|Using Variables
|EG19_~e1~_~e2~_002.tcf
|-
|Adjust Event Variables
|EG19_~e1~_~e2~_003.tcf
|-
|Apply Loss Factors
|EG19_~e1~_~e2~_004.tcf
|-
|Logic Control
|EG19_005.tcf
|}

=Archive Dataset=
Historic example model datasets can be accessed via the following link: [[TUFLOW_Classic_Example_Model_Archive| TUFLOW Classic Example Model Archive]].

=Contact=
For comments, requests and feedback contact [mailto:support@tuflow.com support@tuflow.com]. 
For further training opportunities see [https://tuflow.com/training/training-course-catalogue/ TUFLOW Training Catalogue] and/or contact [mailto:training@tuflow.com training@tuflow.com]. 

 
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TUFLOW 2D Hydraulic Structures

2026-04-07T23:27:15Z

Emilie Nielsen: /* 2D Structure Modelling Theory */

= 2D Structure Modelling Theory =
The theory behind the modelling of energy losses and affluxes of hydraulic structures is presented in the following webinars by Bill Syme and Greg Collecutt (TUFLOW Developers).

*[https://www.tuflow.com/library/webinars/#structures Webinar Link: Modelling Energy Losses at Structures] 
*[https://www.tuflow.com/library/webinars/#nov2022_hydraulic_modelling_bridge Webinar Link: 1D, 2D & 3D Hydraulic Modelling of Bridges]
 

= 2D Bridge Modelling in TUFLOW - Overview =
The TUFLOW 2D solution explicitly predicts the majority of “macro” losses due to the expansion and contraction of water through a constriction, or around a bend, provided the resolution of the grid is sufficiently fine ([https://www.tuflow.com/Download/Publications/Flow%20Through%20an%20Abrupt%20Constriction%20-%202D%20Hydrodynamic%20Performance%20and%20Influence%20of%20Spatial%20Resolution,%20Barton,%202001.pdf Barton, 2001]; [https://www.tuflow.com/Download/Publications/Modelling%20of%20Bends%20and%20Hydraulic%20Structures%20in%20a%202D%20Scheme,%20Syme,%202001.pdf Syme, 2001]; [https://www.tuflow.com/Download/Technical_Memos/Modelling%20Bridge%20Piers%20in%202D%20using%20TUFLOW.pdf Ryan, 2013]). Where the 2D model is not of fine enough resolution to simulate the “micro” losses (e.g. from bridge piers, vena contracta, losses in the vertical (3rd) dimension), additional form loss coefficients and/or modifications to the cells widths and flow height need to be added.
==Contraction/Expansion Losses (“Macro” Losses)==
Loss of energy is caused by the flow contraction during the expansion of water after the vena-contracta inside a bridge section and the flow expansion downstream a bridge. As discussed above, this type of "macro" losses can be explicitly resolved by the TUFLOW 2D solver, provided that a proper turbulence model and mesh size are used. Below is an example of the 2D modelling of flow contraction/expansion at a pair of bridge abutments.
 
[[File:FC_Velocity_Example.PNG|600px]] 

==Pier Losses==
Piers are usually smaller than the 2D cell size in real-world flood models. Although flexible mesh solver or quadtree refinement can be applied to reduce the local cell size around the pier, it also comes with an expensive computational cost that could significantly increase the simulation time. More practically, the backwater effect of piers can be modelled as sub-grid form losses.

Pier form loss coefficients can be derived from information in publications such as [https://www.fhwa.dot.gov/engineering/hydraulics/library_arc.cfm?pub_number=1&id=5 ''Hydraulics of Bridge Waterways'' (Bradly, 1978)] or [https://austroads.com.au/publications/bridges/agbt08 ''Guide to Bridge Technology Part 8: Hydraulic Design of Waterway Structures'' (AUSTROADS, 2018)]. Energy loss estimated from bridge piers or other obstructions, vertical or horizontal, that do not cause upstream controlled flow regimes like pressure flow, are dependent on the ratio of the obstruction's area perpendicular to the flow direction to the gross flow area of the bridge opening, the shape of the piers or obstruction, and the angularity of the piers/obstruction to the flow direction. For example, using Hydraulics of Bridge Waterways (Bradly, 1978) the approach is:
<ol>
<li>Calculate the ratio of the water area occupied by piers to the gross water area of the constriction (both based on the normal water surface) and the angularity of the piers. These inputs are used to calculate "J" in the FHA documentation.</li>
<li>Use the Figure 7 ''Incremental Backwater Coefficient for Piers'' data to calculate Kp. 
[[File:FHA_Kp_arrow_crop.png|400px]]
 
'''NOTE''': the pier form loss coefficients in Hydraulics of Bridge Waterways are derived based on the cross-sectional averaged velocity through the bridge opening in the absence of piers. It's not necessary to specify a blockage value if a pier form loss coefficient estimated from this method is used.
</li>
</ol>

==Bridge Deck and Rail (Super Structure)==
When a bridge deck become partially or completely submerged, the deck could generate extra afflux resulting in increased water levels and flood extents upstream of the structure. The flow around the deck is highly 3-dimentional and complexed due to the different deck designs/profiles and/or the occurrence of pressure flow. In 2D SWE solver, depth-varying form loss values are often needed to reproduce the afflux caused by such structure. Due to the complexity of the flow, guidelines on how to set the form loss coefficient for the bridge deck are rare. We have carried out a joint research with QLD TMR (Queensland Department of Transport and Main Roads) regarding how to choose a proper form loss value for the bridge deck [https://tuflow.com/media/7554/2022-bridge-deck-afflux-modelling-benchmarking-of-cfd-and-swe-codes-to-real-world-data-collecutt-et-al-hwrs.pdf (Collecutt et al, 2022)] . In the research, CFD modelling was conducted to investigate the characteristics of energy loss of a simple bridge with a flat bottomed deck and guardrails.
 
[[File:CFD_study.png|600px]]

Below are the key findings from the study:
*The results displayed a characteristic shape for head loss coefficient as a function of downstream water level over the deck thickness (TW/T).
*The head loss (afflux) peaks when the water level is approximately 1.6*T above the bridge soffit, and decays slowly as the bridge becomes progressively drowned out.
[[File:FormLoss_vs_TWT.png|600px]]
 

=== Bridge Design (hB/T) vs Form Loss Coefficient Table===
The peak loss coefficient value is a function of the ratio of the depth underneath the deck (hB) and the thickness of the deck (T). This table can be used to estimate the deck form loss coefficient based on the bridge design (hB/T).
<ol>
{| style="text-align: center;" class="wikitable" width="35%"
! style="background-color:#005581; font-weight:bold; color:white;" width=55%| Deck Height to Thickness Ratio
! style="background-color:#005581; font-weight:bold; color:white;" width=45%| Peak Form Loss Coefficient
|-
| Scenario A (hB/T) = 2 || 0.42
|-
| Scenario B (hB/T) = 4 || 0.28
|-
| Scenario C (hB/T) = 6 || 0.20
|}
</ol>

*The solid portion of the guard rails (blockage * rail depth) can be added to T in addition to the deck thickness to calculate hB/T.
*For bridge with more complicated designs (e.g. girders), higher form loss might be required due to the higher surface roughness of the bridge.
*If the hB/T ratio is less than 2 or greater than 6, use a peak form loss coefficient of 0.42 (minimum) or 0.20 (maximum), respectively.

'''NOTE''': This form loss value should not be confused with the value of 1.56 used in the pressure flow approached adopted in [[1D_Bridges | TUFLOW 1D "B" and "BB" bridge]]. TUFLOW 1D bridge pressure flow approach is based on the section 4.13.2 "All Girders in Contact with Flow (Case II)" of ''Guide to Bridge Technology Part 8: Hydraulic Design of Waterway Structures'' (AUSTROADS, 2018). The original hydraulic experiment conducted by [https://hdl.handle.net/10217/39009 Liu et al (1957)] in a laboratory flume with a pair of bridge abutments and a deck. The flow conditions were similar to orifice flow due to the high blockage ratio caused by the abutments and the deck. When modelling bridges in 2D, the contraction/expansion losses caused by the abutments would be handled explicitly by the 2D solver, so a value 1.56 can lead to duplication of the contraction/expansion losses caused by the bridge abutments. 
 

=TUFLOW 2D Bridge Setup=
There are two methods available to model depth varying form loss of a bridge structure:
* [[TUFLOW_2D_Hydraulic_Structures#2D_Layered_Flow_Constriction_.282d_lfcsh.29 |2D Layered Flow Constriction (2d_lfcsh)]]
:The traditional method used to model depth-varying form loss through bridge components such as piers, decks, and rails.

*[[TUFLOW_2D_Hydraulic_Structures#2D_BG_Shape_.282d_bg.29 |2D BG Shape (2d_bg)]] (introduced in the 2023 release)
:A simplified approach developed to simplify the model input based on the findings from the joint TMR Study [https://tuflow.com/media/7554/2022-bridge-deck-afflux-modelling-benchmarking-of-cfd-and-swe-codes-to-real-world-data-collecutt-et-al-hwrs.pdf (Collecutt et al, 2022)].

Both methods provide options for representing flow surcharging, the pressure flow of bridge decks and eventually submerged bridge flow at higher water levels. During the surcharging of bridge decks, higher energy losses can be specified to simulate the pressure flow.

Examples for how to configure both approaches are provided in the 2D structures section of the [[TUFLOW_Example_Models#2D_Structures |TUFLOW Wiki Example Models]] and [[Tutorial_M04 |Tutorial Module 4]] - 2D Bridges.

==2D Layered Flow Constriction (2d_lfcsh)==
Four flow constriction layers are represented in a 2d_lfcsh layer. The lower three layers represents the pier, the bridge deck and the rails. Each layer has its own attributes to specify the blockage and the form loss coefficient. The top (fourth) layer assumes the flow is unimpeded, representative of flow over the top of a bridge. Within the same shape, the invert of the bed, and thickness of each layer can vary in 3D.

The following table provides an overview for how to determine the blockage and form loss coefficient for each layer: 
{| style="text-align: left; margin-left: 0; " class="wikitable" width="80%"
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Layer
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Description
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Blockage (%)
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Form Loss Coefficient (FLC)
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Notes
|-

| 1 || Pier layer || ~5% (can be omitted if included in FLC) || Estimate using [[TUFLOW_2D_Hydraulic_Structures#Pier_Losses | Pier Losses]] || Represents flow obstruction from piers beneath the bridge deck
|-
| 2 || Bridge deck || 100% || Use calibration data, if available, to determine FLC. If no calibration is available, estimate using [[TUFLOW_2D_Hydraulic_Structures#Bridge_Design_.28hB.2FT.29_vs_Form_Loss_Coefficient_Table | hB/T vs FLC]] table || Full blockage, no flow through the deck
If using the [[TUFLOW_2D_Hydraulic_Structures#Bridge_Design_.28hB.2FT.29_vs_Form_Loss_Coefficient_Table | hB/T vs FLC]] table, it is recommended to enable the Method C Form Loss Approach
|-
| 3 || Bridge rails || 10% – 100% || Use calibration data, if available, to determine FLC. 
If no calibration data is available, combined FLC for Layers 2 and 3 should be estimated using the [[TUFLOW_2D_Hydraulic_Structures#Bridge_Design_.28hB.2FT.29_vs_Form_Loss_Coefficient_Table | hB/T vs FLC]] table, where T = L2_Depth + (pBlockage × L3_Depth)
*(pBlockage × L3_Depth) represents the solid portion of the rails
*L2 FLC and L3 FLC should sum to the combined FLC
|Blockage and FLC depends on rail type Sensitivity testing with 100% blockage is recommended due to potential for debris during flood
If using the [[TUFLOW_2D_Hydraulic_Structures#Bridge_Design_.28hB.2FT.29_vs_Form_Loss_Coefficient_Table | hB/T vs FLC]] table, it is recommended to enable the Method C Form Loss Approach
|-
| 4 || Above rails || 0% || 0 || Represents unimpeded overtopping flow
|}
<ol>
[[File:2d_lfcsh_attributes.png | 500px ]]
</ol>
 

===Blockage===

The 2d_lfcsh functions by adjusting the flow width and the form loss of 2D cell faces. The combined blockage across the 4 layers is calculated at each simulation timesteps:
<ol>
 
[[File: Blockage_total_equation_01.png|600px]]
 
where 
'''''yi''''' is the actual depth of water in layer '''''i''''' 
'''''ytotal''''' is the total water depth 
</ol>

===Form Loss Approach===

The combined form loss coefficient is determined using one of three methods. The form loss coefficient method can be specified either individually using the 2d_lfcsh “Shape_Options” attribute or globally using the .tcf command: 
<tt>Layered FLC Default Approach == [ METHOD A | {METHOD B} | METHOD C | METHOD D]</tt> 

:METHOD A: The losses are accumulated as the water level rises through the layers. 
<ol>
[[File:Eq_flc_cumulate.png |450px]]
</ol>
:*Layer 1: Constant form loss (L1_FLC)
:*Layers 2 & 3: Form loss increases based on the depth of water in layer 2 & 3; peak form loss at top of Layer 3
:*Above Layer 3: Applies the full accumulated form loss continuously, even when overtopping begins (no reduction)
:Note: Simpler method but tends to overestimate losses when the structure is submerged or overtopped 

:METHOD B (default): the losses are applied pro-rata according to the depth of water in each layer. 
<ol>
[[File:Eq_flc_portion.png |430px]]
</ol>
:*Layer 1: Constant form loss (L1_FLC)
:*Layers 2 & 3: Form loss increases based on the depth of water in layer 2 & 3; peak form loss at top of Layer 3
:*Above Layer 3: Total form loss gradually reduces as water overtops the structure
:Note: Maintains backward compatibility but may underrepresent losses during pressurised or overtopped flows 

:METHOD C (recommended): hybrid approach combining Method A and Method B. 
<ol>
[[File:Eq_flc_methodC.png |520px]]
</ol>
:*Layer 1: Constant form loss (L1_FLC)
:*Layers 2 & 3: Gradual increase in form loss with water level, following Method A
:*Above Layer 3: Total form loss gradually reduces as water overtops the structure, following Method B
:Note: Recommended method; aligns closest to CFD modelling results and TUFLOW HPC behaviour.

:METHOD D: Allows the modeller to control the depth at which the losses start to reduce when the flow transitions between pressure flow and drowned flow.
:This approach is the same used by the 2d_bg layer (introduced in the 2023-03 release). It is recommended to use the 2d_bg layer as it has the benefit of a simplified attribute table, for easier user input.

===Form Loss Calibration Example - Iowa River Flood Study===

In this study, a combined form loss coefficient of 0.35 was used to match observed head loss during slight overtopping of a bridge. The FLC values for each layer were adjusted to achieve the correct combined form loss. The table and plot show how each layer contributes to the total form loss and highlight the differences in calculated form loss between the three methods.

{| style="text-align: left; margin-left: 0;" class="wikitable" width="60%"
!colspan="1" rowspan="2" style="background-color:#005581; font-weight:bold; color:white;" width=6%| Layer
!colspan="1" rowspan="2" style="background-color:#005581; font-weight:bold; color:white;" width=10%| Depth (m)
!colspan="1" rowspan="2" style="background-color:#005581; font-weight:bold; color:white;" width=12%| Blockage (%)
!colspan="2" style="background-color:#005581; font-weight:bold; color:white;" width=20%| Method A
!colspan="2" style="background-color:#005581; font-weight:bold; color:white;" width=20%| Method B
!colspan="2" style="background-color:#005581; font-weight:bold; color:white;" width=20%| Method C
|-
! style="background-color:#005581; font-weight:bold; color:white;"| Layer FLC
! style="background-color:#005581; font-weight:bold; color:white;"| Combined FLC
! style="background-color:#005581; font-weight:bold; color:white;"| Layer FLC
! style="background-color:#005581; font-weight:bold; color:white;"| Combined FLC
! style="background-color:#005581; font-weight:bold; color:white;"| Layer FLC
! style="background-color:#005581; font-weight:bold; color:white;"| Combined FLC
|-
| 1 || 5.0 || 5 || 0.07 || 0.07 || 0.07 || 0.07 || 0.07 || 0.07
|-
| 2 || 1.5 || 100 || 0.15 || 0.22 || 1.05 || 0.30 || 0.15 || 0.22
|-
| 3 || 1.0 || 50 || 0.13 || 0.35 || 0.70 || 0.35 || 0.13 || 0.35
|}

</ol>
 
<ol>
[[File:FLC_vs_height_updated.png | 600px ]]
</ol>

==2D BG Shape (2d_bg)==
2D BG Shape is similar to the Layered Flow Constriction, but has several updates to simplify the input based on the findings from the joint study with TMR [https://tuflow.com/media/7554/2022-bridge-deck-afflux-modelling-benchmarking-of-cfd-and-swe-codes-to-real-world-data-collecutt-et-al-hwrs.pdf (Collecutt et al, 2022)].

The following table provides an overview of how to determine the blockage and form loss coefficient for each layer: 
{| style="text-align: left; margin-left: 0; " class="wikitable" width="80%"
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Layer
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Description
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Blockage (%)
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Form Loss Coefficient (FLC)
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Notes
|-

| 1 || Pier layer || ~5% (can be omitted if included in FLC) || Estimate using [[TUFLOW_2D_Hydraulic_Structures#Pier_Losses | Pier Losses]] || Represents flow obstruction from piers beneath the bridge deck
|-
| 2 || Bridge deck || 100% || rowspan="2" | The Super Structure (Super_S) is the bridge deck and rails layers combined. 
Use calibration data, if available, to determine FLC. 
If no calibration data is available, the Super_S FLC should be estimated using the [[TUFLOW_2D_Hydraulic_Structures#Bridge_Design_.28hB.2FT.29_vs_Form_Loss_Coefficient_Table | hB/T vs FLC]] table, where T = Deck_Depth + (Rail_pBlockage*Rail_Depth)
*(Rail_pBlockage*Rail_Depth) represents the solid portion of the rails
|| Full blockage, no flow through the deck
|-
| 3 || Bridge rails || 10% – 100% || Sensitivity testing with 100% blockage is recommended due to potential for debris during flood events
|-
| 4 || Above rails || 0% || 0 || Represents unimpeded overtopping flow
|}

<ol>
[[File:2d_bg_attributes.png | 700px ]]
</ol>

===Inflection Point===

Based on findings from the joint study [https://tuflow.com/media/7554/2022-bridge-deck-afflux-modelling-benchmarking-of-cfd-and-swe-codes-to-real-world-data-collecutt-et-al-hwrs.pdf (Collecutt et al, 2022)], the head loss peaks when the water level is approximately 1.6*T above the bridge soffit, and decays slowly as the bridge becomes progressively drowned out. The 'SuperS_IPf' attribute (inflection point factor, default = 1.6) can be used to define the height of the inflection point. The solid portion of the rail layer is also added to the deck thickness to calculate the depth to the inflection point (DIP), i.e.:
<ol>
[[File:eq_flc_bg_infection_point.png | 520px ]]
</ol>

===Form Loss Approach===
The form loss approach is similar to the FLC approach METHOD C, with L2/L3 replaced by a single super structure layer:
<ol>
[[File:eq_flc_bg.png | 480px ]]
</ol>

===Form Loss Calibration Example - Iowa River Flood Study===
This example uses the same bridge setup described in the[[TUFLOW_2D_Hydraulic_Structures#Form_Loss_Calibration_Example_-_Iowa_River_Flood_Study | 2D Layered Flow Constriction]] section, with the following parameters applied:
*SuperS_FLC = 0.28
*SuperS_Ipf = 1.6,
The Depth to Inflection Point (DIP) is calculated as 3.2m above the bridge soffit.

The table and figure below show how the form loss value varies with water depth.
<ol>
{| style="text-align: center;" class="wikitable" width="32%"
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;" width=8%| Layer
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;" width=8%| Depth (m)
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;" width=8%| Blockage (%)
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;" width=8%| Form Loss
|-
| Pier || 5.0 || 5 || 0.07
|-
| Deck || 1.5 || 100 || rowspan="2" | 0.28
|-
| Rail || 1.0 || 50
|}

[[File:FLC_vs_height_bg.png | 600px ]]
</ol>

== 2D Bridges Line vs Polygon Layer ==
The form loss coefficient (FLC) is applied differently when using a line compared to a polygon for both 2d_lfcsh and 2d_bg inputs. The FLC is applied at cell sides (u and v faces) as this is where velocities are calculated. 
For larger bridges that spread across multiple cells, it is recommended to use a polygon layer, which selects all u and v faces falling within the polygon.
 
 
'''2D Layered Flow Constriction (2d_lfcsh)'''
{| style="text-align: left; margin-left: 0;" class="wikitable" width="80%"
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 7.5%;"| Geometry
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 7.5%;"| Line Type
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 11%;"| Width Attribute
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 22%;"| FLC Input
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 22%;"| FLC Applied
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 30%;"| Notes
|-
!rowspan="3" | Line
| Thin
| zero
| Total form loss of the bridge
| Applies the FLC to a single row of cell sides
| This approach is cell size independent. It is the easiest setup and the preferred / recommended approach when using 2d_lfcsh.
|-
| Thick
| between zero and 1.5 times the cell size
| Total form loss of the bridge
| FLC/2 applied to all sides of the selected cells
| A cell is selected if the polyline intersects the cell crosshair. Caution should be taken when using a "thick" line, as changes in cell size can cause it to become a "wide" line. If this occurs, the FLC attribute may need to be recalculated to avoid overestimating or underestimating losses.
|-
| Wide
| larger than 1.5 times the cell size
| Total form loss of the bridge ''(may need to be recalculated, see notes)''
| FLC divided by number of cell sides in the direction of flow 
''(number of cell sides in the direction of flow is calculated as line width divided by cell size)''
| Polygon shapes are recommended if more than 3 rows of faces must be selected.. 
Caution should be taken when using a "wide" line. The cell size and alignment of the 2d_lfcsh line may result in selecting too many or too few cell faces in the direction of the flow. The FLC input may need to be recalculated to ensure FLC Applied multiplied by the number of cell sides in the direction of flow equates to the intended total form loss.
|-
!rowspan="1" | Polygon
| -
| -
| Total loss per unit length (meters or feet) in the direction of flow
| FLC * cell size applied to all sides of selected cells
|
|}

'''2D Bridge (2d_bg)'''
{| style="text-align: left; margin-left: 0;" class="wikitable" width="80%"
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 7.5%;"| Geometry
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 7.5%;"| Line Type
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 11%;"| Width Attribute
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 22%;"| FLC Input
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 22%;"| FLC Applied
!colspan="1" style="background-color:#005581; font-weight:bold; color:white; width: 30%;"| Notes
|-
!rowspan="3" | Line
| Thin
| zero
| Total form loss of the bridge
| Applies the FLC to a single row of cell sides.
| This approach is cell size independent.
|-
| Thick
| larger than zero
| Total form loss of the bridge
| FLC/2 applied to all sides of the selected cells
| This approach is cell size independent. A cell is selected if the polyline intersects the cell crosshair.
|-
| Wide
| Not supported
| –
| –
| BG polygon shapes are recommended if more than 3 rows of faces must be selected.
|-
!rowspan="1" |Polygon
| -
| ''(used to automatically distribute the total FLC to the selected faces)''
| Total form loss of the bridge
| FLC / Deck_Width * cell size applied to all sides of selected cells
| For bridges modelled using a 2d_bg polygon the relative ratio of the bridge width to the 2D cell size should be 4 or greater. For more information on this see [https://downloads.tuflow.com/Other/2d_bg_R_Bridge_Configuration_Advice_202503.pdf 2d_bg_R_Bridge_Configuration_Advice.pdf].
|}
 
The following diagrams demonstrate how the input FLC is applied for the four geometry options for 2d_lfcsh and 2d_bg layers: 
[[File:2dlfcsh 2dbg combined v2.png|1200px]]

It is good modelling practice to check the [[Check_Files_2d_lfcsh_uvpt | lfcsh_uvpt_check]] and [[Check Files 2d bg uvpt check | bg_uvpt_check]] files to confirm the number of faces selected and the FLC values assigned. It is also strongly recommended to undertake a sensitivity analysis on the applied form losses in the model to check if it makes any difference to the results and/or double check against other methods (hand calculations, other software, CFD modelling), especially if the bridge is near an area of interest. If calibration data is available, this should be used to guide the form loss value specification. 
 

= Common Questions Answered (FAQ)=
== What blockage values should I use for bridge guard rails? ==
The blockage of bridge guard rails can be anything from 100% blocked (solid concrete rails) to 10% blocked (very open rails). In addition, the accumulation of debris during a flood can be substantial as shown in the image below. Sensitivity testing with 100% blockage is recommended.
 
[[File:Bridge rail debris.jpg | 500px]]

== How to conduct sensitivity test for 2D bridges? ==
General recommendations to cross-check the results are:
* Compare computed affluxes against desktop methods (e.g. Hydraulics of Bridge Waterways, 1978) and/or other software including CFD, especially for unusual bridge designs.
* Use any recorded flood marks or general observations from past events to check and calibrate FLC values.
* Conduct sensitivity testing by assessing the impact and influence of FLC values on your modelling objectives. The afflux resulting from the FLC values will be proportional to the velocity head, i.e. ∆h=FLC*(v^2/2g). As such, if velocities are low (e.g. 1 m/s), the results may not be overly sensitive to uncertainties in the FLC values. If completing a check using this equation for a long skew bridge it is best to calculate the total structure velocity from a PO line digitised in the same location as the bridge.

Finally, after completing sensitivity testing and understanding the range of uncertainty due to unknowns like the degree of blockage and influence of FLC values (e.g. +/-20%), you are in a position to discuss with your client how best to proceed. For example, if the modelling is to set planning levels for a development upstream then it may be appropriate to choose values on the higher side (higher FLC values and/or blockage assumptions), noting that the uncertainty may be amply covered by a regulatory freeboard. Conversely, if the development is on the downstream side the conservative approach would be to use the results at the lower end of your FLC/blockage values. 
[[File:Bridge Flood Debris Loading.jpg | 500px]] 

== Should I use both FLC and blockage for layer one in 2D bridge layered flow constriction? ==
When applying FLC and blockage values to model obstructions such as piers, the following considerations need to be taken into account:
* The FLC value applies an energy loss along 1D channels or across 2D cell faces equivalent to FLC*V2/2g where V is the 1D channel velocity or the 2D cell face velocity.
* FLC values are often sourced from publications such as Hydraulics of Bridge Waterways or AustRoads (e.g. Kp chart for piers).
* If possible, establish whether the source of the FLC value is based on the approach velocity (the velocity in the absence of piers) or structure velocity (the velocity with area blocked out by the piers) noting that it often isn’t clear or stated.
** If it is the structure velocity, this is usually the velocity at the vena-contracta (point of greatest contraction within the entrance to the structure and therefore highest velocity) - see image below. Bluff or sharp-edged obstructions will have a much more pronounced vena-contracta, and therefore higher velocity compared with a round-edged obstruction.
** FLC values based on the approach velocity will be higher than those based on the structure velocity to achieve the same energy loss.
* Applying a blockage equivalent to the obstruction width will increase, usually very slightly, the velocity of the 1D channel or 2D cell face. This won’t be the vena-contracta velocity, but a velocity between the approach velocity and the vena-contracta velocity. A greater blockage will need to be applied to emulate the vena-contracta velocity.
* If the FLC source value is based on:
** The approach velocity then there is no need to apply a blockage value.
** The structure velocity then the blockage value should be applied noting that it may be appropriate to apply a larger blockage to take into account the vena-contracta.
* If it is not clear or unknown whether the FLC source value is based on the approach or structure velocity, the recommendation would be to apply the blockage in the interests of being slightly conservative on the upstream flood level calculation.
* For most minor obstructions such as bridge piers, the blockage is usually relatively small and whether included or not has a negligible or minor affect on flood levels compared with other factors such as the approach embankments and the bridge deck.
* Blockage from debris wrapped around piers can have a greater influence on the results than the effect of applying or not applying a blockage. Debris wrapped around piers can be accounted for in the FLC value calculated for the pier layer.
* As always, sensitivity testing with and without blockage and +/- the FLC value is highly recommended to understand their importance in regard to the broader modelling objectives and the effects of uncertainties in the input data, boundaries, other parameters such as Manning’s n values, and the accuracy of the numerical solution scheme (see [https://www.tuflow.com/library/webinars/#maximise_accuracy Maximising the Accuracy of Hydraulic Models webinar]).
[[File: Vena_contracta.png]] 
''Image showing the formation of the vena-contracta.'' 
 

==I don't see results that I expect when using 2d_lfcsh layer==
The 2d_lfcsh layer is a versatile feature that was designed to model bridges in 2D, but can also be used for other applications like fences, buildings raised on pillars and so on.
Some of the unexpected results could be:
* Water level going through the bridge deck in 2D map output.
* Water transiting through 100% blocked Layer 1, e.g. fences with solid base.
* SHMax.csv reporting values above the bridge deck when 2D map output reports water level lower than the top of the bridge deck.

TUFLOW is a 2D solution (not 3D), in the 2d_lfcsh layer the percent blockage and form loss coefficient applied to the cell faces is depth averaged across the entire cell face (across Layer 1, 2 and 3): 
*For bridges, where Layer 2 has a 100% blockage applied, the minimum flow width of 0.001m is used and is averaged with the Layer 1 blockage (based on the depth of the water). This may result in a water level being reported within or above the bridge deck, which would represent the pressure head.
*Layered flow constriction works by adjusting the flow area of the cell faces by any blockages to generate the correct depth averaged velocity at each face at which the form losses are applied as a fraction of the V2/2g kinetic energy. Calculating the correct velocity is critical for determining the losses as the losses are proportional to the velocity squared. 
*For a layered flow constriction cell face the flow area cannot be zero above the invert of Layer 1 to avoid a divide by zero in the computations, therefore a minimum average flow width after applying blockages of 0.001 m is applied. if Layer 1 is 100% blocked, a very small amount of water will flow through Layer 1. If this is unacceptable, instead of applying 100% blockage of Layer 1, the preferred approach is to start the layered flow constriction at the top of Layer 1 or raise the ground elevation to the top of Layer 1 using one of the Z Shape modification functions (e.g. a breakline). 
<ol>
[[File:100% Blockage Diagram.png | 500px]]
</ol>

== Can I model bridge piers explicitly in 2D using very small cells? ==
It isn't recommended to explicitly model bridge piers by blocking out the pier faces in TUFLOW, or in any hydraulic modelling software based on solving Shallow Water Equations(SWE). Due to the 3-dimentiality of the flow and turbulence around a pier, computational fluid dynamics (CFD) approach is often required to simulate the flow around piers explicitly. The wake turbulence behind a simple-shape pier can be resolved to some extent using extremely fine mesh in TUFLOW (see calibration example to a flume experiment in the [https://www.tuflow.com/library/webinars/#structures webinar on Energy Losses at Structures]), however the predictions for head losses show notable sensitivities to the mesh size, the mesh design, and the choice of turbulence model. The extremely fine mesh resolution also results in significantly higher computational costs.

Therefore, the safest and strongly recommended approach with regard to establishing head losses and consequently flood levels, is to model the effects of such obstructions with form loss coefficients (applied to selected mesh cells) that have been derived from physical testing. This approach has been shown to provide the most consistent results across various mesh resolutions. It also has the added benefit that, by avoiding small cells in the mesh, it will provide much more efficient run times for flow solvers.

[[File:Flow round a cylinder.png]]

''The point of flow separation around an object has a major bearing on the drag coefficient and is not reliably reproduced by 2D or 3D software.''


== How to best convert flow constriction data (2d_fc or 2d_fcsh) into newer formats (2d_lfcsh or 2d_bg)? ==
The form loss parameters can be transferred from the flow constriction (2d_fc or 2d_fcsh) to the first layer of the layered flow constriction (2d_lfcsh) or pier layer of the 2d_bg. Definition of the remaining form loss and blockage layer inputs should follow the guidance outlined in [[TUFLOW_2D_Hydraulic_Structures#2D_Layered_Flow_Constriction_.282d_lfcsh.29 | 2D Layered Flow Constriction]] and [[TUFLOW_2D_Hydraulic_Structures#2D_BG_Shape_.282d_bg.29 | 2D BG Shape]] paragraphs. 
When using floating pontoon (type FD in the 2d_fc or 2d_fcsh) different setup might need to be used for different events. For large events when floating pontoon becomes fixed at the top of the supporting piles, standard 2d_lfcsh setup can be used. Smaller events when the pontoon is floating at different heights might require more sensitivity testing of the structure parameters to find out a setup the matches the reality as close as possible. 

== Should I model bridges in 1D or 2D Domain? ==
The recommended approach typically depends on the study objectives and if the channel upstream and downstream of the bridge is modelled in 1D or 2D. To preserve the momentum as accurately as possible the bridge should be modelled in the same dimension as the channel, e.g. 1d_nwk bridge if the channels is in 1D and 2d_bg or 2d_lfcsh if the channel is modelled in 2D. 
In 2D, the expansion/contraction losses are modelled based on the topography and don't need to be estimated as attributes as for 1D modelling. Also, for higher flows where the bridge is overtopped, 2D is preferable approach.

== What is the difference between downstream and upstream controlled flow? ==
Downstream control means a change in downstream water level will cause a change in upstream water level. Upstream control means the upstream water level is insensitive to the downstream water level and usually indicates the occurrence of supercritical flow.

== What FLC values should be used for 2d_bg bridge if hB/T is below 2 or above 6? ==
TMR has extended the CFD simulation to hB/T ratios of 1 to 10. Refer to the [https://docs.tuflow.com/classic-hpc/manual/latest/ TUFLOW Manual] for details.

If hB/T is outside this ratio:
* hB/T ratios of less than 1 represent a very unusual bridge sitting low to the ground, and the peak FLC may increase above the end value (FLC of 0.6) in a way that doesn't follow the research trend or extrapolation. For these cases we would recommend using CFD modelling to obtain a more informed value. Alternatively, computing an FLC based on pressure flow or using 1D culvert might be considered.
* For hB/T ratios of greater than 10, the FLC is likely to continue to decrease, but probably not significantly. Clamping to the end value (FLC of 0.16) might be considered the more conservative approach (if the primary concern is flood levels upstream of the bridge). 
 
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TUFLOW Viewer - Plotting 1D Flow Regime

2026-04-07T23:19:06Z

Emilie Nielsen:

===Tool Description===
Flow regime can be a very useful output to understand and debug 1D results, in particular, culverts. 

Flow regime results are output from ESTRY by default (i.e. there is no special output type or command required in the ECF). Since the 2020-01-AA TUFLOW release, flow regime results will be imported into TUFLOW Viewer when time series results are loaded. There are several methods to view the flow regime results:
<ol>
<li>Select 'Flow Regime' in the '''Result Type''' widget (underneath 'Time Series'). 
[[File: TUFLOW Viewer_Plotting 1D Flow Regime_1a.png]] 
This will display the flow regime as points and lock the y-axis to the available flow regime types as per the [https://docs.tuflow.com/classic-hpc/manual/latest/ TUFLOW Manual]. The plot will group the types by outlet and inlet control regimes - 'G' is no flow, everything below 'G' on the plot will be inlet control and everything above 'G' is outlet control. 
[[File: TUFLOW Viewer_Plotting 1D Flow Regime_2a_03.png]] 

<li>Right clicking certain time series results [[File:results_2.png | 15px]] (e.g. 'Flow', 'Level', or 'Velocity') will give the user the option of checking on '''Flow Regime'''. 
[[File: TUFLOW Viewer_Plotting 1D Flow Regime_3a.png]] 

This will plot the flow regime as letters and map it to the chosen result type, making visualising the results a lot easier. For example, in the image below the jump in velocity at approximately 0.55 hrs to 0.7 hrs is shown to be a change in flow regime (it goes from 'A' to 'B' then to 'L'. 
[[File: TUFLOW Viewer_Plotting 1D Flow Regime_4a.png]]
</ol>

'''Flow Regimes (Source: TUFLOW Manual)''' 
[[File:Plotting_TimeSeries_FlowRegime_Legend.PNG]] 

===Example===
{{Video|name=TUFLOW Viewer_Plotting 1D Flow Regime_1a.mp4|width=1350}}
 

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