Estimating of the USLE topographic factor using three algorithms

Abstract

Several researchers have proposed the mathematical modeling of the topographic factor (slope length and slope steepness) of the Universal Soil Loss Equation (USLE) in different conditions of relief. This paper presents an analysis of the performance of three equations in the production of the topographic factor as well as the influence of slope steepness in its estimation. Topographic data processed in a geographic information system were used to derive the digital elevation model that was applied to calculate the topographic factor using the software USLE-2D. Differences between the results when using distinct algorithms were found and areas with larger slope steepness resulted in greater differences. The slope corresponded to 75.1%, 83.8% and 82.8% of the topographic factor in the studied equations. Therefore, the slope has more influence than the length of the ramp in the calculation of the topographic factor. In addition, the choice of the equation to be applied to obtain such factor is dependent upon the local relief.