STUDY OF SEDIMENT DELIVERY RATIO IN SIWALIKS

Abstract

Previously sediment yield was adopted as equivalent to gross erosion or soil. loss from upland area. Theoretical and experimental results later on indicated that the sediment yield may not be equal to the gross erosion. The ratio of sediment yield and gross erosion is known as sediment delivery ratio (SDR). Knowledge of this ratio is important for optimal planning and design of several developmental activities. A brief review of literature reveals that, for estimating SDR, two approaches are in use. One attempts to observe sediment yield, and gross erosion individually and ratio of that gives SDR. In another approach several empirical relationships have been proposed to estimate SDR on the basis of catchment and cliMatic 'factors. It has been found that the rainfall, runoff, slope factor, watershed area, relief and length are the most influencing parameters in the estimation of SDR. In the present study, SDR has been computed for the Siwaliks using the sediment routing approach for calculating sediment yield, gross erosion has been calculated using universal soil loss equation (USLE). Integrated use of satellite data product, insitu observation and laboratory experimentation have been made to assess the various parameters needed to estimate SDR namely land cover, pedologic information travel time, rainfall and runoff. The study reveals that the numerical value of SDR for Siwaliks varies between 1.65 to 1.73 in spatial domain and 0.36 to 1.72 in temporal domain. It has also been noticed that antecedent moisture condition (AMC) and curve number (CN) are the most infuencial parameters. The study reveals that Siwaliks are highly prone to erosion