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=Model Mesh Size vs Remap Result=
Beside the quality of hazard output discussed above, the model mesh size can stillalso impact the remapped output inat thelocation with followingsteep situationsslope.
==Road Crest==
At location with steep slope, typically whenWhen water flows over a road crest, the remapped water depth may become negative if the output grid size is too largecoarse. The figure below shows the remapped depth over a road crest from models with different mesh sizes ranging from 5m to 1.25m. As can be seen, some area doesn't have remapped outputdepth despite the water is clearly over-topping the road. <br>
[[File:Fig9 road mesh size.png|1050px]]<br>
'''Figure 9 Remapped depth over a road crest from different mesh size models.'''<br><br>
As illustrated in the figurenext belowfigure, the DEM has mush smaller resolution and the elevation changes rapidly overat the road crest, when interpolation the coarser water level grids to the finer DEM, the interpolated water level may become lower than the local DEM level, due to the difference in grid resolution. In the actual2D simulationsolver, this type of location is treated as 'weir flow' and proper depth is used for calculation. ThisHowever, issuethis is not reflected in the depth output yet and will be further addressed in the high resolution SGS output scheduled in the future release.<br>
[[File:Fig10 road mesh size2.png|500px]]<br>
'''Figure 10 Modelled water level line over the road crest.'''<br>
==Upstream Catchment==
In direct rainfall model, modellers can also benefit from applying relatively large mesh size and SGS method at the upstream region of a catchment. The SGS faces correctly capturingcapture the lowest elevationelevations along the gullies to preserve the sub-cell scale flow paths, which improves the hydrologic response for a whole catchment modelsmodel (see Kitts et. al., 2020, will add link to Duncan's paper in https://www.tuflow.com/Library.aspx??? when it is uploaded). TheseHowever, upstreamif the cell willsize begets treatedtoo aslarge partiallyat wetthe cell,upstream howeverregion, whichonly maysmall portion of the cell becomes wet due to the large difference in elevation inside a cell. This makemakes the depth plotting extremely challenging and the remapped depth may become negative even though water is flowing through a valley. InThe blue contour below shows the simulationremapped thesewater cellsdepth of a 60m mesh whole catchment direct rainfall model. As can be seen the flow paths are oftennot treatedcontinuous along some valleys. The remapped water depth from a 20m mesh model is also plotted as 'shallowthe sheetred contour underneath the 60m result. The flow' path has becomes clearer as the mesh size is refined. <br>
[[File:Fig11 Innisfall remapped D.png|500px]]<br>
'''Figure 11 Remapped depth at upstream catchment from different mesh size models..'''
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