Soil Loss Estimation Using GIS and Remote Sensing Techniques: The Case of Debis Watershed, Blue Nile Basin Ethiopia

Abstract

Soil erosion is one of the pressingproblems in highland of Ethiopia.  To reduce this problem estimating amount of soil at watershed level is necessary. However, in Ethiopia area specific up to date information in many catchments (watershed) is still found to be lacking. Therefore, this research was carried out to spatially estimate the soil loss rate of Debiswatershed with a Geographic Information System (GIS) and Remote Sensing (RS)technique. Revised Universal Soil Loss Equation (RUSLE) adapted to Ethiopian conditions was used to estimate potential soil losses by utilizing information on rainfall erosivity(R) using interpolation of rainfall data, soil erodibility(K) using soil map, vegetation cover (C) using satellite images, topography (LS) using Digital Elevation Model (DEM) and conservation practices (P ) using satellite images.  Result from analysis shows that soil erosion risk differs spatially in the study area because of its rugged topography, geomorphology, landform, soil types, land cover, and land use. The spatial locations of the high spot area for soil erosion in the study revealed that the potential soil loss is typically greater along the steeper slope banks of tributaries. Based on the level of soil erosion rates, the study area was divided into five priority categories for conservation interventions. About 51% (229 sqr.km) of the watershed was categorized none to slight class values ranging from 0.5 to 10 tons ha-1yr-1. The remaining 49 % (1376.48 ha) of land was classified under moderate to high class, which is greater than the maximum tolerable soil loss (11 tons ha-1 y-1).Thus, governmental,non-governmental organization and community found in watershed should focus on applying soil and water conservation intervention which helps to reduce the problem.

Keywords:  Debis, Soil erosion,  RUSLE, Remote sensing, GIS ,Watershed