Estimation of Slope Length Value of RUSLE Factor L Using GIS

The universal soil loss equation (USLE) and its main derivate, revised universal soil loss equation (RUSLE), have been used all over the world to estimate the soil loss. Specific effects of topography over soil erosion are estimated through the LS factor as the product of slope length factor L and slope steepness factor S. New procedures, based on geographic information systems (GIS), have been developed to estimate the slope length (lambda) in hydrographic basins. Slope length (lambda) is defined as the distance from the point of origin of overland flow to the point where either the slope gradient decreases enough that deposition begins, or runoff water enters a well-defined channel. The purpose of this research was to compare two methodologies based on GIS, Hickey and Sextante, for obtaining the slope length value (lambda). Both methodologies make a valid slope length (lambda) concept interpretation; nevertheless, the Hickey method was specifically made for slope length calculation, as it incorporates a variable cut-off slope angle that improves the detection of the beginning and the end of each slope length (lambda).