TUFLOW Output Discussion: Difference between revisions
Content deleted Content added
No edit summary |
|||
Line 54:
== How do I apply high resolution (HR) output and what are the options? ==
See the <u>[[TUFLOW_HR_Output | TUFLOW HR Output]]</u> Wiki page for details.<br>
== Why are there differences between high resolution grid from TUFLOW and remapped outputs generated by the asc_to_asc utility? ==
Line 86 ⟶ 85:
Water level outputs, however, assume that water fills from the bottom of the SGS cell’s storage curve. This water level result is recorded at the cell centre, interpolated to the cell corners, and then the gridded outputs are triangulated from these points (orange line). In sheet flow situations when the volume in that cell is small, the cell-centered water level may sit below the terrain (blue dot on diagram) if the cell is steep enough. This can result in a water level results sitting below the DEM_Z, even when there is a positive depth result. Note this does not affect the simulation computationally, only how the water level results are output. <br>
[[File:SGS_Sheetflow_Waterlevel.jpg|600px]]
== How should below ground water surface elevation (WSE) in wet SGS cells be interpreted or presented? ==
Below ground WSE in wet SGS cells is a known output behaviour in SGS enabled models and does not indicate an error in the hydraulic solution.
This occurs because TUFLOW reports water level assuming water fills from the lowest part of the SGS cell during output. As a result, cells may be wet while the reported water surface elevation remains below the cell centre ground level.
This behaviour commonly occurs in the following situations:
'''Channel edge partial wetting'''
* Partially wet cells along channel banks may contain water that does not reach the cell centre elevation.
* In this case, compare the standard water surface elevation with the standard DEM Z check file to confirm consistency with terrain levels.
'''Shallow sheet flow from rainfall or side inflow'''
Cells may be wet but still report water surface elevation below the cell centre ground level because the depth is small and distributed across the SGS terrain.
'''Presentation and reporting considerations'''
* A presentation method is to post process results by adding the cell averaged depth output <font color="blue"><tt>SGS Depth Output == CELL AVERAGE</tt></font> to the DEM elevation to derive an above ground water level.
* This approach can improve the visual representation of shallow flooding in sheet flow areas but may produce unrealistic water levels in fully wet or partially wet cells.
* Conditional logic may be required to determine where the standard water surface elevation or a derived depth plus DEM level should be presented based on the local flow condition.
== Why do the high-resolution (HR) mapped results have a significantly smaller extent than the standard (non-HR) grid outputs for a sub-grid-scale (SGS) direct rainfall HPC model? ==
| |||