Methods of spatial representation to calculate the topographic factor (LS) of the Revised Universal Soil Loss Equation (USLE) have been used to estimate soil erosion and sediment yield of watersheds. These procedures are based on equations traditionally used to determine the LS factor and information that characterize the hillslope forms and processes, derived from the Digital Elevation Model (DEM). Two computational methods commonly used to calculate LS factor in soil erosion and sediment yield models were analyzed in this study. The analysis was performed in four small rural watersheds with hilly terrain. The LS values obtained by the methods of spatial representation were compared with each other with LS values measured by the traditional method. Results show significant differences of the computer-generated LS values, which were related to the calculation procedure and the method used to determine the DEM flow direction. Differences were also observed between the numeric values of the LS factor determined by methods of spatial representation and in the field.
Revised Universal Soil Loss Equation; sediment yield; hillslope erosion; numeric terrain modeling; geographic information systems
