TUFLOW HR Output: Difference between revisions
Content deleted Content added
Created page with "Page Under Construction Introduction There are a variety gate configurations that can be modeled within TUFLOW including operational gate structures. Gates are commonly u..." |
Anne.Kolega (talk | contribs) |
||
| (61 intermediate revisions by 4 users not shown) | |||
Line 1:
=Introduction=
High-Resolution (HR) Grid/Raster Map Outputs was first introduced in TUFLOW 2020-10-AB release. When an SGS model uses “<font color="blue"><tt>SGS Approach </tt></font> <font color="red"><tt>== </tt></font> <font color="black"><tt>Method C</tt></font>”, the sampled elevations are retained at the end of the geometry processing. These sub-grid elevations include topography modifiers such as breaklines, and they allow a high-resolution elevation check file to be written and used for high-resolution depth map outputs. Currently, ASC, FLT and TIF raster formats are supported.
Example models with high-resolution outputs are available in the <u>[[TUFLOW_Example_Models|TUFLOW Example Models]]</u> dataset.
For the HR output, the water level at each HR output location is interpolated from the computed 2D water levels (see <u>[[#Water_Level_Interpolation_Methods|Water Level Interpolation Methods]]</u> for details). The depth output is calculated differently for standard and high-resolution outputs:
:* Standard depth output: The depth is calculated at cell centres and corners first, then interpolated to the standard output grid locations (default is half the cell size). This is shown in the image on the left.
:* High-resolution depth output: The depth is the difference between the interpolated water level and the sub-grid elevation. This is shown in the image on the right.<br>
<br>
[[File:Sgs_std_output.png|360px]] [[File:Sgs_hr_output.png|360px]]
The advantage of the HR output is that it can retain the sub-grid detail of the terrain information even at a coarse cell size. As compared in the example below, the HR depth output shows a clear flow path even at a 100m grid. However, nicer depth output does not mean reliable hydraulic result. In fact, the 100m cell size is too coarse to produce reliable/converged hydraulic results for any real-world flood model. It's is strongly recommended that the model convergence/benchmarking tests are conducted based on the standard map output. The HR output should be used for presentation purpose only.
[[File:Sgs_std_vs_hr_output.png|720px]]
=Enable High-Resolution Output=
To produce high-resolution output, add “HRASC”, “HRFLT” or “HRTIF” to the “<font color="blue"><tt>Map Output Format </tt></font> <font color="red"><tt>==</tt></font>” .tcf command. Note that if a HR output is defined in this command, a high-resolution DEM_Z check file ([[Check_Files_2d_DEM_Z_HR |_DEM_Z_HR]]) is produced instead of the [[Check_Files_2d_DEM_Zmin|_DEM_Zmin]] check file. For example:
:<font color="blue"><tt>Map Output Format </tt></font> <font color="red"><tt>== </tt></font> <font color="black"><tt>XMDF TIF HRTIF</tt></font>
Currently, water level and depth are the only supported high-resolution output formats, i.e.:
:<font color="blue"><tt>HRTIF Map Output Data Types </tt></font> <font color="red"><tt>== </tt></font> <font color="black"><tt>h d</tt></font>
The map output data types and map output interval can be defined separately for the high-resolution output formats. For example:
:<font color="blue"><tt>Map Output Data Types</tt></font> <font color="red"><tt>== </tt></font> <font color="black"><tt> h d</tt></font> <font color="green"><tt>! Outputs water levels and depths (regular)</tt></font>
:<font color="blue"><tt>Map Output Interval </tt></font> <font color="red"><tt>== </tt></font> <font color="black"><tt>600</tt></font> <font color="green"><tt>! Sets all map output intervals to 600 seconds</tt></font>
:<font color="blue"><tt>HRTIF Map Output Data Types</tt></font> <font color="red"><tt>== </tt></font> <font color="black"><tt> d</tt></font> <font color="green"><tt>! Outputs HR (TIF format) depths</tt></font>
:<font color="blue"><tt>HRTIF Map Output Interval </tt></font> <font color="red"><tt>== </tt></font> <font color="black"><tt>3600</tt></font> <font color="green"><tt>! Sets HR (TIF format) map output interval to 3600 seconds</tt></font>
The output resolution for high-resolution output grids can be defined using the following .tcf command. It can be defined in meters or feet. If this command is omitted, the default output resolution is set to the SGS sampling distance:
:<font color="blue"><tt>HR Grid Output Cell Size </tt></font> <font color="red"><tt>== </tt></font> <font color="black"><tt>0.5</tt></font> <font color="green"><tt></tt></font>
HR outputs are supported by HPC and Quadtree Output Zones. Below is an example of .tcf commands to set up HR output in an output zone:
<font color="blue"><tt>Model Output Zones</tt></font> <font color="red"><tt>==</tt></font> <font color="black"><tt>ZoneA</tt></font><br>
<font color="blue"><tt>Define Output Zone</tt></font> <font color="red"><tt>==</tt></font> <font color="black"><tt>ZoneA</tt></font>
<font color="blue"><tt>Read GIS Output Zone</tt></font> <font color="red"><tt>==</tt></font> <font color="black"><tt>..\model\gis\2d_oz_S05_002_R.shp</tt></font>
<font color="blue"><tt>Write Check Files INCLUDE</tt></font> <font color="red"><tt>==</tt></font> <font color="black"><tt>dem_Z</tt></font> <font color="green"><tt>! includes only dem_Z check file for this output zone</tt></font>
<font color="blue"><tt>Map Output Format</tt></font> <font color="red"><tt>==</tt></font> <font color="black"><tt>HRTIF</tt></font>
<font color="blue"><tt>HRFLT Map Output Data Types</tt></font> <font color="red"><tt>==</tt></font> <font color="black"><tt>h d</tt></font>
<font color="blue"><tt>HRFLT Map Output Interval</tt></font> <font color="red"><tt>==</tt></font> <font color="black"><tt>3600</tt></font>
<font color="blue"><tt>HR Grid Output Cell Size</tt></font> <font color="red"><tt>==</tt></font> <font color="black"><tt>0.5</tt></font>
<font color="blue"><tt>End Define</tt></font>
=Water Level Interpolation Methods=
Similar to the standard output, the HR output needs to interpolate cell centre water levels to cell corners. However, the interpolation methods for the standard output (<font color="blue"><tt>Map Output Corner Interpolation </tt></font> <font color="red"><tt>== </tt></font> <font color="black"><tt>Method C</tt></font>) can produce "bumpy" HR water level outputs in direct rainfall models with steep terrain, as the water level is linearly interpolated from the cell centres/corners, while the change of sub-grid elevations may not be linear. This often happens between fully wet cells and sheet flow cells, as illustrated below.
[[File:corner_h_intp_output.png|480px]]
In the HR water level output, these locations often have high water level with triangular shape.
[[File:HR_Intp_A.png|480px]]<br>
'''Method A HR Interpolation Approach''' (gray lines show the triangulation TINs)
Two additional methods have been added for the HR corner water level interpolation:
<font color="blue"><tt>HR Interpolation Approach </tt></font> <font color="red"><tt>== </tt></font> <font color="black"><tt>Method A | Method B | {Method C}</tt></font>
* Method A applies the same water level interpolation method used for the standard output.
* Method B performs sheet flow checks at cell faces and ignores the water level from the upstream cell.
* Method C is the default option that applies the same sheet flow checks as the Method B. In addition, it also uses the number of wet SGS sampled points as a weighting that biases non-sheet flow cells that further improves the mapping to in-stream water levels.
The two images below present the high-resolution water level output at the same location, but with <tt><font color=blue>HR Interpolation Approach </font><font color=red>==</font> Method B</tt> and <tt>MethodC</tt>. As can be seen, the water level along the narrow stream is “smoother”.
[[File:HR_Intp_B.png|480px]] [[File:HR_Intp_C.png|480px]]<br>
'''Method B (left) and Method C (right) HR Interpolation Approach'''
Note that when these two methods are applied, the interpolated corner water level is biased to the non-sheet flow cells, and consequently, sheet flow cells may appear as “dry” cells. The improved approach takes into account that the sheet flow water level is currently under development.
Whilst Methods B and C can substantially improve the water surface mapping of SGS models using direct rainfall (rain-on-grid), there will always be inaccuracies with mapping at a higher resolution than the 2D cell resolution due to interpolation and extrapolation. Regardless of the software, the greater the ratio of 2D cell size to the high-resolution DEM cell size, the greater the potential for mapping inaccuracies. Should better mapping accuracy be required, reducing the 2D cell size to compute the spatial variation in water surface and velocities more accurately is by far the best course of action.
=Interpolation near Thin Breaklines =
Thin breaklines are often used to define hydraulic controls, such as levees and road embankments. These controls often experience upstream controlled weir flow, where the water levels on the two sides of the breakline can be considerably different. Retaining just one water level (upstream, downstream or average) at output points along the breakline may result in unsatisfactory water level map output as illustrated in the two figures below. This issue becomes more profound the larger the 2D cell size.
: '''Note:''' This feature only works for thin breaklines in Z Shape (2d_zsh) layers. Thick/wide breaklines raise more than 1 row of cell centres and 2 rows of cell faces, and thus do not experience this HR interpolation issue.
[[File:breakline_h_intp_output.png|480px]]<br>
[[File:HR_thin_brk_off.png|480px]]<br>
'''HR Thin Z Line Output Adjustment == OFF'''
A new HR output feature has been introduced to improve the water level interpolation along thin breaklines.
For any further questions please email TUFLOW support: [mailto:support@tuflow.com?Subject=TUFLOW%201D%20gates%20help support@tuflow.com]
<font color="blue"><tt>HR Thin Z Line Output Adjustment </tt></font> <font color="red"><tt>== </tt></font> <font color="black"><tt>OFF | {ON CELL SIDES} | ON ALIGNMENT</tt></font>
* OFF: does not apply any water level adjustment.
* ON CELL SIDES (default): two water levels, rather than one, are stored at cell corners selected by thin breaklines. These water levels are used to interpolate HR water levels on either side of thin breaklines. This option produces a sudden drop in water level across the breakline as illustrated in the figure below, noting the sudden drop follows the 2D cell faces where the breakline is applied.
* ON ALIGNMENT: As an extension to the “ON CELL SIDES” option, this method moves and aligns the 2D cell corner vertices to the original alignment of the breakline for producing HR water level and depth. The arrows in the figure below show how vertices of the TIN are moved to align with the breakline. This can produce substantially improved high-resolution mapping along thin breaklines with substantial drops in water levels, especially for larger 2D cell sizes. Note that the cell corners are NOT shifted for the hydraulic calculations.
[[File:HR_thin_brk_on.png|480px]] [[File:HR_thin_brk_on_adj.png|480px]]<br>
'''HR Thin Z Line Output Adjustment == ON CELL SIDES (left) and ON ALIGNMENT (right)'''
=Showing Face Elevations in _DEM_Z_HR Check File =
When modelling breaklines in TUFLOW, thin breaklines modify the cell face elevations but do not modify the cell storages. When outputting the high-resolution outputs, the user can choose whether the cell face elevations are included using the following .tcf command.
<font color="blue"><tt>HR Grid Output Use Face Elevations </tt></font> <font color="red"><tt>== </tt></font> <font color="black"><tt>{ON} | OFF</tt></font>
* ON (default): Use face elevations in [[Check_Files_2d_DEM_Z_HR | _DEM_Z_HR]] check file. This option accurately shows the cell faces where water can be hydraulically blocked. However, when cell faces are angled with the thin breakline, this can create 'pockets' of lower elevations in the check file that do not exist in reality.
* OFF: Face elevations are not used in [[Check_Files_2d_DEM_Z_HR | _DEM_Z_HR]] check file. This is an useful option for report writing, as 'clean' high-resolution DEM images can be generated reflecting all geometry updates except for the Thin Breakline updates at cell faces.
[[File:HR_Z_Use_Face_Elevations_ON.PNG|480px]] [[File:HR_Z_Use_Face_Elevations_OFF.PNG|480px]]<br>
'''HR Grid Output Use Face Elevations == ON (left) and OFF (right)'''
<br><br>
{{Tips Navigation
|uplink=[[ TUFLOW_Output_Discussion | Back to TUFLOW Output Discussion]]
}}
| |||