Topography

WAM requires a Digital Elevation Model (DEM) that is used to determine the flow directions for overland flow routing. Overland flow is routed to the nearest downhill reach. Using a high-resolution DEM is not required since WAM will resample the DEM to use the specified grid cell size when calculating the unique grids. However, a high-resolution DEM (e.g., Lidar) is very helpful in setting up the stream network since water features such as streams and canals are frequently visible in high-resolution datasets.

The DEM is not imported as part of the regular "Import GIS Data" command so it must be done using regular ArcMap tools. If the elevations in the DEM are not in meters, a new DEM should be constructed by multiplying the values by the appropriate factor. This is done because the DEM is used to determine stream elevations during the reach network building process, and WAM relies on elevations being in meters.

The DEM should be clipped to the basin boundary and copied into the WAM GIS Database and named "RawDEM".