Estimation of soil erosion and sediment yield using GIS

A Geographical Information System (GIS) based method is proposed and demons trated for the identification of sediment source areas and the prediction o f storm sediment yield from catchments. Data from the Nagwa and Karso catch ments in Bihar (India) have been used. The Integrated Land and Water Inform ation System (ILWIS) GIS package has been used for carrying out geographic analyses. An Earth Resources Data Analysis System (ERDAS) Imagine image pro cessor has been used for the digital analysis of satellite data for derivin g the land cover and soil characteristics of the catchments. The catchments were discretized into hydrologically homogeneous grid cells to capture the catchment heterogeneity. The cells thus formed were then differentiated in to cells of overland flow regions and cells of channel flow regions based o n the magnitude of their flow accumulation areas. The gross soil erosion in each cell was calculated using the Universal Soil Loss Equation (USLE) by carefully determining its various parameters. The concept of sediment deliv ery ratio (SDR) was used for determination of the total sediment yield of e ach catchment during isolated storm events.