ABSTRACT:The proliferation of watershed databases in raster Geographic Information System (GIS) format and the availability of radar‐estimated rainfall data foster rapid developments in raster‐based surface runoff simulations. The two‐dimensional physically‐based rainfall‐runoff model CASC2D simulates spatially‐varied surface runoff while fully utilizing raster GIS and radar‐rainfall data. The model uses the Green and Ampt infiltration method, and the diffusive wave formulation for overland and channel flow routing enables overbank flow storage and routing. CASC2D offers unique color capabilities to display the spatio‐temporal variability of rainfall, cumulative infiltrated depth, and surface water depth as thunderstorms unfold. The model has been calibrated and independently verified to provide accurate simulations of catchment response to moving rainstorms on watersheds with spatially‐varied infiltration. The model can accurately simulate surface runoff from flashfloods caused by intense thunderstorms moving across partial are
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