Preparing the DG2-related DEM files using generateDG2DEM toolkit

As opposed to piecewise-constant data representation used in the FV1 or ACC solvers, the DG2 solver represents data as piecewise-planar per element, defined by three coefficients: an average-coefficient and two slope-coefficients in X and Y directions (Shaw et al., 2021).

Hence, setting up the DG2 on LISFLOOD-FP requires three separate Esri ASCII raster files: one for the average-coefficient values, and two others for the X-directional and the Y-directional slope-coefficient values, with the extensions .dem, .dem1x and .dem1y, respectively.

Files with the extensions .dem, .dem1x and .dem1y can be generated using the toolkit generateDG2DEM (available in the preprocess directory of LISFLOOD-FP-trunk repository). The toolkit is obtained after compiling the LISFLOOD-FP code, following the instructions within “Compilation”. It will be generated as an executable file with the name generateDG2DEM.exe on a Windows platform and the name generateDG2DEM on a Linux-based platform, in the same directory of the LISFLOOD-FP executable.

The toolkit requires the availability of the raw DEM file in the same directory, subject to appending it with the extension .raw. For example, the DEM file, merewether-0p175m.dem, created for the Merewether test case (recall “Modifying the resolution of the DEM on QGIS”) must be renamed to merewether-0p175m.dem.raw.

For running the generateDG2DEM.exe of the Merewether test case on Windows, create a directory for the test case, for example named merewether, inside the same directory where generateDG2DEM.exe is located. Then place the merewether-0p175m.par and merewether-0p175m.dem.raw files inside the merewether directory. By clicking on the location bar of the Windows Explorer, then typing cmd and pressing Enter, the Command Prompt Window will be opened in the folder. To run the toolkit, the name of the executable must be entered in the Command prompt, followed by the name of the .par file:

..\generateDG2DEM.exe merewether-0p175m.par   

After running the generateDG2DEM toolkit, three raster files will be generated within the same directory of merewether-0p175m.dem.raw file:

• merewether-0p175m.dem which is a copy of the same merewether-0p175m.dem.raw file, containing the generated average-coefficient values

• merewether-0p175m.dem1x which contains the generated X-directional slope-coefficient values

• merewether-0p175m.dem1y which contains the generated Y-directional slope-coefficient values

Important note. Running any of the ACC, FV1 and DG2 solvers on any of DEM files generated by generateDG2DEM toolkit results requires modifying the coordinates the points specific in the .stage file as explained in section “Input file including the positions where water depth and velocity histories are to be extracted (.stage)”.

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