Estimation of upland erosion using GIS

The Universal Soil-Loss Equation (USLE) is a widely used method for calculating annual soil erosion losses, based on rainfall, runoff, slope, runoff length, soil type, and landuse parameters. The equation was originally developed on small agricultural plots, but has since been adopted for evaluating erosion from large watersheds under a wide range of landuses. This study was designed to compare USLE calculations in a GIS environment at grid sizes ranging from 30 x 30 m up to 6 x 6 km. The analysis of two watersheds in Mississippi shows that large grid sizes tend to underestimate soil losses. At grid sizes exceeding 100 x 100 m, a correction factor must be included in the calculations. With the use of the correction factor, the USLE can be applied directly at macroscales, providing an important tool for studies of basin-wide upland erosion rates. The proposed method is shown to be applicable for large watersheds under different climates. (C) 1998 Elsevier Science Ltd. All rights reserved.