Assessment Of Soil Erosion Risk Using Rusle And Gis: A Case Study Of Beles Sub-Basin, North-Western Blue Nile, Ethiopia

Abstract

Soil erosion by water is a serious environmental problem that affects environmental quality, agricultural productivity and sustainability of downstream structures and resources. The impacts of soil erosion could be worst in the developing countries including Ethiopia. Assessment of soil erosion is useful in planning and soil conservation works. The objective of this study was to assess soil erosion risk in the Beles sub basin located in the Metekel Zone of Benishangul-Gumuz and Awi Zone of Amhara National Regional State, north western part of Ethiopia. The study was conducted using the Revised Universal Soil Loss Equation (RUSLE) model with GIS. The model incorporate rainfall, soil, land cover and digital elevation model data to generate RUSLE parameters. The rainfall erosivity factor was derived from mean annual rainfall data of nearby rain gauge stations and the soil map data of the study area was used to generate soil erodibilty factor. A digital elevation model (30 m x 30 m resolution) was used to delineate the study area and analysis slope factor. The land use/cover map of 2013 was used to generate crop management factor and conservation practices factor. The five factors raster maps were multiplied in GIS raster calculator and the spatially distributed annual soil loss rate map was determined. The result shows that the amount of soil loss from the study area ranges from zero up to 370 ton ha-1 yr -1 . The average annual soil loss rate for the entirely area was estimated at 8.39 ton ha-1 yr - 1 and the total annual soil loss potential was 11.91Million ton yr -1 for the whole area. Based on the results, about 15.85 % of the study area has soil loss that was above the maximum tolerable soil loss of 11 ton ha-1 yr -1 . The method (RUSLE) used as erosion assessment model has given up a fairly reliable estimation of soil loss rates in the study area that helps to delineate erosion prone areas and prepare conservation plans for efficient use of resources. Therefore, the model could be applied in other watershed or basin for assessment, delineation and prioritization of erosion prone areas for conservation interventions. Those areas with high soil erosion rate needs immediate and appropriate intervention of soil conservation measures that needs the collaboration of all the stakeholders.