RISK ASSESSMENT OF SOIL EROSION IN RA WAL WATERSHED USING GIS & RS TECHNIQUES

Abstract

Soil erosion due to water is becoming a serious land degradation problem in rain fed areas of Pothwar region. Rawal lake, a major source of water supply for Islamabad and Rawalpindi is undergoing heavy sedimentation due to soil erosion and its storage capacity has reduced over the past few decades. This research aims to assess soil erosion risk in Rawal watershed using COordination of Information on the Environment (CORINE). The factors considered in this model are soil, precipitation, temperature, slope and vegetation cover. The soil maps were used to extract soil texture, soil depth and stoniness data which were overlaid to generate soil erodibility map. The precipitation and temperature data of 18 years (1988- 2005) was used to compute Modified Fournier Index (MFI) and Bagnouls-Gaussen aridity Index (BGI) that was overlaid to generate erosivity map. Slope was generated from DEM of 20m spatial resolution which was extracted from topographic sheet of scale 1 :25,000. Soil erodibility, erosivity and slope maps were overlaid to produce potential soil erosion risk. NDVI was also calculated using SPOT-5 satellite image to generate vegetation cover. Finally, actual erosion risk map was prepared by overlay analysis of potential erosion risk map and vegetation cover. The results indicated that 25, 48 and 27 per cent of the study area were under low, moderate and high erosion risks, respectively. Soil loss computed for both potential (28 tons/ha/yr) and actual erosion risks (24 tons/ha/yr) by CORINE model integrated with GIS and RS techniques proved efficient arid inexpensive in generating soil erosion risk maps. This research can be helpful in improving land management and soil conservation for the areas of high erosion risk.