Modelling soil erosion risk in a mountainous watershed of Mid-Himalaya by integrating RUSLE model with GIS

Abstract

Soil erosion is one of the major cause of land degradation and is a serious threat to foodsecurity and agricultural sustainability. Revised Universal Soil Loss equation (RUSLE)model using remote sensing (RS) and Geographical Information Systems (GIS) inputswas employed to estimate soil erosion risk in a watershed of mid-Himalaya inUttarakhand state, India. Spatial distribution of soil erosion risk area in the watershedwas estimated by integrating various RUSLE factors (R, K, LS, C, P) in raster based GISenvironment. RUSLE model factor maps were generated using remote sensing satellitedata (IRS LISS III and LANDSAT-8) and Digital elevation model. Agriculture (59%) wasfound to be the dominant land use system followed by scrub land (20%) in thewatershed. Rainfall erosivity (R) factor was estimated using past 23 years rainfall data.SRTM DEM was used to generate slope length –steepness (LS) factor in this highlyrugged terrain. Nearly 70% of the watershed is having steep to moderately steep slope(>40%). Satellite data was interpreted to prepare physiographic map at 1:50,000 scale.Surface soil samples collected in each physiographic unit was analyzed to generate soilerodibility (K) map. Soil erodibility factor ranged from 0.033 to 0.077 in the watershed.Soil erosion risk analysis showed that 36.25%, 9.31%, 15.80%, 15.27%, 11.46% and11.89% area of watershed falls under very low, low, moderate, moderate high, high andvery high erosion risk classes respectively. The average annual erosion rate waspredicted to be 65.84 t/ha/yr. The soil erosion rates were predicted to vary from 3.24t/ha/yr in dense mixed forest cover to 87.98 t/ha/yr in open scrub land. The soilerosion map thus generated employing remote sensing and GIS techniques, can serveas a tool for deriving strategies for effective planning and implementation of variousmanagement and conservation practices for soil and water conservation in thewatershed.