DEM Based Overland Flow Routing Model

Abstract

A physically based, distributed rainfall-runoff event model is developed to route overland flows from flat agricultural watersheds. The model works on a cell basis and routes overland flows from one cell to the next following the maximum downslope directions. The model is able to consider spatially-varied data of soils, crops, land slopes, and aspects, which can be extracted from geographic information systems (GIS) and from digital elevation models (DEMs). Because of this feature, the model can be used for evaluating the impacts of agricultural practices on surface runoff. To describe overland flows on flat watersheds, the model uses the diffusion wave approximation of the St. Venant equations for computing the hydrograph. The computation is accomplished using the MacCormack scheme, a second order accurate numerical method. The model was tested against analytic solutions of the kinematic wave equations and was applied to route the overland flows across Goodwater Creek, a USDA research watershed. The model was calibrated using 26 events and verified using 11 events. The results show that the model works well.