FMA Challenge 3: Difference between revisions
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It is up to the modeler's discretion to determine what GIS package to use, what text editor to use, and how to run their models (batch mode or within the text editor).All relevant files can be found on '''FMA_Challenge_Models/FMA_Scenario3/'''
=Solution to Challenge 3=
A sample solution has been presented, courtesy of BMT WBM.
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[[File:FMA3_6.jpg|600px]]
=Solution to Challenge 3+=
Where unstated, the same parameters were used as per Challenge 3.
==Computational Domain Assembly and Execution==
The 100ft and 200ft models were used from Challenge 3 with the Creek Manning’s n value set to 0.2.
The soils layers provided were roughly classified into two soil types for the purposes of demonstrating the Green-Ampt infiltration feature in TUFLOW. The soils are shown in the image below where:
<ol>
<li>Red indicates a Sandy Loam.
<li>Green is Sand.
<li>The blue cross-hatched areas are the Urban land use zones modeled in Challenge 3. These areas were assigned a 90% impervious parameter that restricts the rate of water entering the underlying soils.</li>
The Green-Ampt parameters used were the USDR soil type classifications which are built into TUFLOW’s internal soils database. The parameters for the two soils are tabulated below.
{| align="center" class="wikitable" width="50%"
! style="background-color:#005581; font-weight:bold; color:white;"| USDR Soil Type
! style="background-color:#005581; font-weight:bold; color:white;" width=50%| Suction (inches)
! style="background-color:#005581; font-weight:bold; color:white;" width=50%| Hydraulic Conductivity (inches/h)
! style="background-color:#005581; font-weight:bold; color:white;" width=50%| Porosity (fraction)
|-
| Sandy Loam || 4.3 || 0.43 || 0.412
|-
| Sand || 1.95 || 4.6 || 0.417
|}
The underlying soil was assumed to have an infinite depth to saturation (saturation depths/levels can be specified as 3D surfaces in TUFLOW if known). The soils were also set to have an initial moisture content of zero.
[[File:FMA3_7.jpg|600px]]
The 100ft and 200ft simulations were re-run with the Green-Ampt infiltration switched on. The resulting peak flood depths map for the 100ft simulation is shown in the image below. As can be seen, the extent of inundation is significantly reduced with floodwaters infiltrating before reaching the model extents or returning to the main channel.
The mass balance reporting from TUFLOW indicates over half (58%) of the water infiltrates into the ground during the 171 hour simulation. For the flow out of the model see “100ft GA” in the chart of flow out of the model presented in Challenge 3.
[[File:FMA3_8.jpg|600px]]
==Challenges==
The soils GIS layers were difficult to work with. There is a lot of detail, but no clear way to correlate the different soils with Green-Ampt parameters (porosity, hydraulic conductivity, suction, etc).
=Conclusion=
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