The study demonstrates Geographic Information Systems (GIS) based methodology for identification of sediment source areas and prediction of storm sediment yield for small watersheds. The Nagwa watershed in Bihar was discretized in to 50m grid cells using Integrated Land and Water Information Systems (ILWIS) GIS package, and unique drainage directions were obtained using GIS analysis. Also, a threshold channel network was generated from Digital Elevation Model (DEM) of the watershed. Actual observed drainage and generated drainage networks were superimposed and were found identical.
Digital analysis of satellite data was carried out using Imagine 8.3.1 and land use and soil maps of the watershed were generated. A GIS based procedure for USLE-LS factor determination for individual grid cells was implemented for the watershed.
After assigning various USLE parameters for individual grid cells based on derived land use and soil map of the watershed, gross surface erosion in each cell is calculated. The eroded sediment is then routed to the catchment outlet using the concept of sediment delivery ratio.
Reasonable results were obtained for storm sediment yield in Nagwa watershed using proposed concepts without any parameter calibration. However to draw definite conclusions for applicability of this methodology without any calibration, more watersheds need to be analyzed.
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