TUFLOW Output Discussion: Difference between revisions

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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 elevationWSE remains below the cell centre ground level.
 
This behaviour commonly occurs in the following situations:
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* 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 elevationWSE with the standard DEM ZDEM_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 elevationWSE 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</tt></font> <font color="red"><tt>==</tt></font><tt> 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 IF logic may be required to determinechoose where the standard water surface elevationto orpresent acell derivedaveraged depth plus DEM leveland shouldwhere beto presentedretain basedthe onstandard theTUFLOW localwater flowlevel conditionoutput.
 
== 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? ==