Effect of Dem Resolutions in the Runoff and Soil Loss Predictions of the Wepp Watershed Model

Erosion prediction utilizing digital elevation models (DEMs) is a logical advancement for automating the simulationprocess for models such as the Water Erosion Prediction Project (WEPP). The effects of using different DEM resolutionson watershed simulations and the ability to accurately predict sediment yield and runoff from different rainfall event sizeswere studied using three application methods and data from six research watersheds. Simulating watersheds with a range ofresolutions can help address the problem of deciding what topographic DEM resolution is ideal for model simulations of thewatershed outlet, the end of each hillslope, and along the slope profiles. The three application methods studied here were:(1) Hillslope - Chanleng, (2) Hillslope - Calcleng, and (3) Flowpath. The two Hillslope methods use a representative slopeprofile to represent each hillslope in the watershed, and the Flowpath method uses all of the individual flowpaths as modelinput for WEPP simulations. Results show that the Hillslope methods were not significantly influenced by DEM resolutions;however, there was an observable interaction between resolutions and the Flowpath method. Large rainfall events were predictedbetter than small events, but fine DEM resolutions did not improve predictions of either large or small rainfall events.Using coarse DEM resolutions for the topographic input will not decrease the accuracy of erosion prediction using the WEPPmodel and the Hillslope methods, unless the coarseness of the DEM compromises the delineation of the watershed or hillslopes.