Soil Erosion Risk Assessment for Prioritization of Soil Conservation Measures Using RUSLE Integrated with GIS in Chemoga Watershed, Upper Blue Nile Basin, Ethiopia.

Abstract

Soil loss by runoff has become series problem in Ethiopian; particularly the northern Ethiopian highlands are among the most seriously affected regions in the country due to highly rugged topography, population pressure, over grazing and cultivation of steep lands and erosive nature of rainfall. Hence, soil erosion risk assessment is critically required for prioritization of soil conservation measures. The main objective of this study is to estimate soil erosion rate and identify hotspot areas of soil erosion to facilitate conservation management practices in Chemoga watershed, Upper Blue Nile Basin, Ethiopia. In this study, RUSLE method was used integrated with GIS technique to estimate soil erosion rate of a watershed and prioritize for soil and water conservation practice. In the study rainfall erosivity factor (R), Length slope factor (LS), soil erodability factor (K), vegetation cover factor (C) and erosion control factor (P) were used as an input to the RUSLE model. The rainfall erosivity factor has been determined from monthly precipitation data. The soil survey data was used to develop the soil erodability factor and the digital elevation model (DEM) of study area was also used to generate topographic factor (LS). The value of cover management factor and support practice factor were obtained from land use land cover map and validated with field observations. The results show that midstream and upstream parts of the watershed is more sensitive to soil erosion than the lower part. In the study, the erosion hazard maps were reclassified for the periodization of the watersheds. Based on the special distribution of the erosion hazards, 4.93% of the watershed area was classified sever soil erosion risk zone (30 up to 50 ton/ha/year) and 4.91% categorized as very sever soil erosion risk zone i.e above 50 ton/ha/year which are situated in the narrowest steep slope parts of the upper catchments of the watershed. These parts of the watersheds were identified as the primary erosion hotspot area which needs immediate attention in terms of management perspective.