Spatial assessment of soil erosion in a hilly watershed of Western Nepal

Soil erosion is a serious problem mankind is facing today as it has been continuously degrading the quality and standard of lives across the globe. Being a hilly country with undulating topography with steeper slopes accompanied with heavy rainfall, Nepal is predisposed to natural hazards including soil erosion. This paper attempts to model the soil erosion rate in the Aringale Khola Watershed of middle hills of Nepal with the judicious use of geographic information system (GIS) and revised universal soil loss equation (RUSLE) techniques. RUSLE was used in ArcGIS environment, taking rainfall-runoff (R), soil erodibility (K), topography (LS), crop management (C) and conservation support practice (P) factors as primary inputs. A total of nine soil erosion classes were observed; soil erosion rates ranging from 0.03 to 100.33 t/ha/year with a mean soil rate of 11.17 t/ha/year. GIS analysis depicted that 36.93% (1256.28 ha) of the total watershed area fell in the severe erosion classes whereas the remaining 63.07% (2145.56 ha) were less severe. A major part of the watershed, particularly areas with higher elevations and steep slopes, are degraded and needs urgent conservation measures. This study is a first attempt to model soil erosion distribution in the Aringale Khola Watershed and has very good potential to be used for soil erosion prediction in similar watersheds in the middle hills of Nepal.