TUFLOW Output Discussion: Difference between revisions

In TUFLOW HPC, the cell averaged depth is used computationally and by default in the depth outputs (see below).

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 cell centreterrain (blue dot on diagram) if the cell is steep enough. This water level is still recorded at the cell centre and used to interpolate the mapped output (orange line). 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>

The high resolution (HR) outputs are based on <u>[[TUFLOW_HR_Output | intersecting]]</u> the standard water level output results with the HR DEM_Z. Due to the <u>[[TUFLOW_Output_Discussion#Why_are_the_values_of_the_mapped_water_level_results_.28h_max.29_lower_than_the_terrain_elevations_.28DEM_Z.29.3F | output limitation]]</u> for sub-grid-scale (SGS) enabled models with shallow sheet flow (particularly direct rainfall models) on sufficiently steep terrain, water levels can be output lower than the DEM_Z terrain elevations. This is due to the assumption (for output purposes) that water fills the SGS cell’s storage curve from the bottom, which differs from the approach of cell-average depth used computationally in TUFLOW HPC and by default in depth outputs. When the HR water level results are processed, the full extent of the standard water level results are intersected with the HR DEM_Z and any water level results that are lower than the HR DEM_Z elevations due to the above effect are trimmed. The extent of the HR water level results are then used to trim allthe otherHR resultsdepth outputs for HR.