Soil Erosion Risk Assessment With Rusle And Gis In Dire Dam Watershed

Soil erosion in Dire dam watershed is a widespread problem causing soil and organic matterrnlosses and hence loss of fertility and reduction in crop yield. In addition to these on-siternproblems, it also produces important off-site effects, like downstream sediment depositions inrnfields, floodplains and water bodies, water pollution, eutrophication and reservoir siltation. Thisrnresearch has, therefore, been carried out to evaluate the soil erosion risk in the watershed. Thernresearch integrates the Revised Universal Soil Loss Equation (RUSLE) with a GeographicrnInformation System (GIS) to quantify the potential soil erosion risk. Rainfall data, soil data,rnDEM data and satellite image were used as input data sets to generate RUSLE factor values.rnRaster calculator was used to interactively calculate potential soil loss and prepare soil erosionrnrisk map. The result showed that the potential annual soil loss of the watershed ranges from 0.00rnto 263.25 ton/ha/yr and the mean annual soil loss rate is 58.3ton/ha/yr. Of the 9 sub-watersheds,rnfour (47.5%) were predicted to experience annual soil loss of more than the watershed’s averagern(58.3 t/ ha/yr), whereas five sub-watersheds (52.5%) estimated annual soil losses were less thanrnthe average. The result also showed that very high soil loss (80.71 t ha/yr) is observed in subwatershedrnB and four sub-watershed (B, E, A & G) fell under very high and high soil erosionrnseverity classes (60.43 – 80.71 t/ha/yr). Based on average annual soil losses, the sub-watershedsrnwere divided into four priority categories for conservation intervention. As a result the criticalrnsub-watersheds which are under very high and high category were selected and recommended tornbe intervened for conservation measures to reduce on-site soil loss and their off-site effects.rnKey Words: Dire Dam, Soil erosion risk, Watershed, RUSLE, GIS

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