Abstract:
Quantifying the amount of the soil loss using GIS and RUSLE helps to substantiate
investment in sustainable land management for the benefit it’s to land users. Soil erosion is
recognized as one of the world's most serious environmental and economic problems. It
deteriorates the soil quality, loss of nutrients ,changes in physical, chemical and biological
processes and reducing agriculture productivity resulting in global food insecurity .Like
other highland parts of Ethiopia, the soil erosion by water is the major factor for soil loss in
the Fincha’a catchment. Hence, the general objective of this research is to Estimate average
Annual Soil Erosion from Upper Fincha’a catchment By Using Revised Universal Soil Loss
Equation (RUSLE. Geographic Information System (GIS) with (RUSLE) was used to estimate
average annual soil loss, sediment yield at the outlet and identify the most vulnerable area of
soil erosion in the Fincha’a catchment. Data that are used for this study was gathered from
different sources such as National Mapping Agency, National Meteorological service
Agency, Ministry of Water, Irrigation and Electricity of Ethiopia. Types of data used was the
monthly precipitation of 24 year (1991-2015) for seven stations, soil data, Digital Elevation
Models (30 x 30m), Land use and land cover data of the study area. Eventually, each of the
RUSLE factors, with associated attribute data were digitally encoded in a GIS database to create
five thematic map layers of each factor. By integrating these five map layers in GIS raster
calculator, the required spatially distributed annual average soil loss rate was determined. The
result showed that the potential annual soil loss rate of the watershed varies from 0 to 375
ton/ha/yr and the mean annual soil loss rate was found to be 31 ton/ha/yr. The total annual
soil erosion from the entire watershed area was about 4.08 Million tons annually. The
estimated sediment yield at watershed outlet was about 386628.6 ton/yr from 1318 square
kilometer by using Sediment Delivery Ratio (SDR) technique. . In present study areas that
were highly vulnerable to soil erosion were characterized by steep slopes, very low
vegetation cover, and high rainfall. The result shows that, it could be difficult to maintain the
sustainability of the soil productivity if the specified much of soil removed annually. It also
reveals that most of the watershed erosion severity evaluated under low and moderate soil
erosion severity classes covering 46 % of the watershed areas which is due to the effect of
Cropland and Sparse forest which shows less vulnerable to soil erosion. In the soil loss rate
map of upper Fincha’a watershed, the steep slope lands of northwest and northeast areas
which were identified as extensive soil loss. Hence, those areas needs immediate attention and
priorities when implementing soil conservation and management activities before the area
jumps to recover soil degradations