Soil Erosion Estimation Using Revised Universal Soil Loss Equation Integrated with Geographic Information System by Different Resolution Digital Elevation Model Data in Weyto Sub-Basin, Southern Ethiopia

Abstract

Soil erosion is a global environmental challenge for developing countries including Ethiopia that require regular monitoring to take corrective measures. In this context, this study was focused on estimating soil erosion using the Revised Universal Soil Loss Equation (rusle) integrated with Geographical Information System (gis) technique for which it applied 30 m and 200 m resolution Digital Elevation Model (dem) data to generate slope gradient and length. Rainfall erosivity, soil erodibility, land cover/use and management factors data were obtained from existing studies and field-based assessments where the data were used to estimate the soil erosion using rusle model in ArcMap under two different dem resolution scenario. The model estimated an average of 1.38 and 1.86 million tons of annual soil loss by water using 200 and 30 meters resolution dem data, respectively, while keeping other factors constant. The erosion estimated using higher (30 m) resolution dem data was more realistic than low (200 m) resolution data , as the higher resolution dem data allowed less generalization. In high resolution dem data, the slopes generated were also more in line with ground reality. Based on the case study of Weyto sub-basin in Southern Ethiopia, we thus conclude that the gis technique and remote sensing data can be used in rusle based erosion risk prediction for large areas even at basin, sub-basin and macro watershed level. We suggest that the accuracy of the prediction can be improved by using high resolution (large scale) input data disaggregated by micro- and sub-watersheds.