Effects of DEM resolution on forest hydrologic and erosion prediction using WEPP

Abstract

The recent modification of WEPP (Water Erosion Prediction Project) has improved theoriginal models applicability to hydrology and erosion modeling in forest watersheds. To generatereliable topographic and hydrologic inputs for the WEPP model, carefully selecting Digital ElevationModels (DEMs) with appropriate resolution and accuracy is essential because topography is a majorfactor controlling water erosion. LIght Detection and Ranging (LIDAR), a new remote sensingtechnology, provides an alternative for generating fine and high-quality DEMs. This study appliesWEPP (v2006.201) for hydrological and erosion simulation under forest conditions and evaluates theeffects of DEM resolution and accuracy on watershed hydrology and water erosion prediction at awatershed scale. Stream flow and total suspended solids (TSS) in two small forest watershedslocated in northern Idaho were collected and processed. A total of six DEMs from three sources(NED, SRTM, and LIDAR) at three resolutions (30 m, 10 m, and 4 m) were obtained and used tocalculate topographic parameters as inputs to the WEPP model. WEPP-simulated hydrologic anderosion results using the six DEMs were compared with the field-observed data. For both studywatersheds, DEMs with different resolutions and sources generated varied topographic andhydrologic attributes, which in turn led to significantly different erosion predictions by WEPP.