Soil Erosion Impact Assessment using USLE/GIS Approaches to Identify High Erosion Risk Areas in the Lowland Agricultural Watershed of Blue Nile Basin, Ethiopia

Abstract

Erosion map of a watershed offers a wealth of knowledge and can be crucial for implementing site-specific management interventions. Thus, watershed-based soil erosion assessment was conducted to recognize erosion hotspot areas, while aiming to roughly calculate the average annual soil loss in Genda-wuha watershed, with a total area of 154,548.5 ha located in the northwest lowland of Blue Nile basin Ethiopia using USLE/GIS approach. Sixteen years of rainfall data, 53 soil sample data, a 30m by 30m digital elevation model (DEM), a land-use/land-cover map, and support practice factor were used to determine high erosion risk areas. The USLE parameters were integrated and analyzed using a raster calculator in the ArcGIS platform to predict and map the mean annual soil loss of Genda-wuha watershed. The result showed that the annual soil loss of the watershed extends from none in the lower and middle part of the watershed to 75.36 Megagram (Mg) ha-1yr-1 in the steeper parts of the watershed with a mean annual soil loss of 7.9 Mg ha-1yr-1. Most of the soil erosion affected areas are spatially situated in the upper steep slope parts of Genda-wuha watershed, which could be as a result of an increased slope gradient and length in the specified location. However, the majority of the watershed (82.62%) was estimated to be low erosion rates varying from 0 to 5 Mg ha–1 yr–1 and these areas correspond primarily to nearly flat landscapes of the watershed.