The Watershed Modeling System (WMS) can be used to automatically delineate watersheds and sub-basin boundaries from digital elevation models (DEMs). WMS uses TOPAZ to delineate grid elevation data. However, flow directions and accumulations may also be computed by ArcInfo, ArcView, or GRASS and imported into WMS in grid ascii format. In this study, TOPAZ is run to determine the flow direction and flow accumulation grids for WMS. TOPAZ (Topographic Parameterization) is an automated digital landscape analysis tool for topographic evaluation, drainage identification, watershed segmentation, and sub-catchment parameterization, and is similar to CRWR- PrePro, which also uses the 8-Direction Point Pour Model.
TOPAZ, shown in Figure 3.17, creates three grids: a new elevation grid (relief.dat), a flow direction grid (flovec.dat) and a flow accumulation grid (uparea.dat).