DEM-based modelling of surface runoff using diffusion wave equation

A digital elevation model (DEM)-based overland flow routing model was developed for computation of surface runoff for isolated storm events. The model operates on a grid or cell basis and routes the rainfall excess generated over the cells, following the DEM-derived drainage paths, to the catchment outlet. The rainfall excess for each cell of the catchment was computed using the Philip two-term infiltration model utilizing the physical properties of the cell. The overland flow was described by a finite volume-based numerical solution of the diffusion wave approximation of the St Venant equations. The cell physical properties, such as topographic characteristics, land use, soil, etc., were extracted from published maps for discretized cells of the catchment using a Geographic Information System. The results of model application indicate that the model satisfactorily predicted the runoff hydrograph. The cell-based structure of the model allowed for generation of spatially distributed catchment information in terms of the model-computed variables, such as the depth of flow and discharge.