Application of InVEST SDR Model to Assess Soil Erosion and Sediment Export: A Case Study from Deduru Oya River Basin, Sri Lanka

Abstract


 The quantification of soil loss and sediment load is an essential step in watershed management in river basins. Soil erosion in the Deduru Oya river basin was assessed using the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) Sediment Delivery Ratio (SDR) model. The Universal Soil Loss Equation (RUSLE) is embedded in InVEST-SDR model. This study used a 30m x 30m digital elevation model (DEM), 20 years of rainfall data measured at five rain gauge stations across the basin; land use – land cover and soil maps of the basin; and also data from the literature as input to the model. The average annual soil loss in Deduru Oya river basin varied from 0 to 277.25 t ha-1 yr-1. About 5.6% of the basin (145.9 km2 area) was identified as having a high rate of soil erosion ( > 12 t ha-1 yr-1 ), and those areas are mainly found upstream of the river basin. The mean annual sediment export from the Deduru Oya basin was estimated to be 0.18 t ha-1 yr-1, and Kiribathgalla and Bambaragahakanda areas showed the highest sediment export values. The prioritization of soil erosion prone areas resulted in this study helps river basin managers to set watershed management plans in the Deduru Oya river basin.