Soil Erosion Risk Assessment in Nashe Dam Reservoir Using Remote Sensing, GIS and RUSLE Model Techniques in Horro Guduru Wollega Zone, Oromia Region, Ethiopia

Abstract

Soil degradation is wide spread and serious throughout the Ethiopian Highlands. It is also a major watershed problem in many developing countries causing significant loss of soil fertility, loss of productivity and environmental degradation. This research has, therefore, been carried out to evaluate the soil erosion risk and quantify the major land use land cover changes over the past 20 years (1996-2016) in the Nashe watershed. The research integrates the Revised Universal Soil Loss Equation (RUSLE) with a Geographic Information System (GIS) and Remote Sensing (RS) to quantify the potential soil erosion risk and land use land cover changes. Rainfall data, soil data, DEM data and satellite image were used as input data sets to generate RUSLE factor values. Raster calculator was used to interactively calculate potential soil loss and prepare soil erosion risk map. For the land use land cover change calculation two satellite images of two year interval (Landsat TM 1996 and Landsat 2016) has been utilized. As a result the potential soil erosion risk and land use land cover map of 1996 and 2016 of the study area was generated. The result showed that the potential annual soil loss of the watershed ranges from 0.00 to 243..065ton/ha/yr. and the mean annual soil loss rate is 45.7ton/ha/yr. Concerning the land use land cover change Grass land decline from (8.85%) to (6.85.4%), open forest changes from (47.10%) to (22.75 %) and settlement land changes from (4.42%) to (7.59%). On the contrary farm land changes from (27.18%) to (45.55%), bare lands increase from (5.40%) to (5.55%) and water body changes from (7.06%) to (12.10 %). By the LULC analysis it has been found that the grass land and forest land declined from 1996-2016. On other hand, the rest of the land cover types have increased.