Evaluation of soil erosion and sediment yield in tropical river basin of the Western Ghats, South India

The Manimala River Basin (MRB), located in the ecologically fragile Western Ghats of Kerala, faces critical soil erosion impacting land, soil, and water quality. This study provides a high-resolution, spatially explicit erosion assessment by integrating GIS-based Revised Universal Soil Loss Equation (RUSLE) and Sediment Delivery Ratio (SDR) models. This study provides a high-resolution, pixel-level assessment of soil erosion using remote sensing and climatic datasets, enabling detailed mapping of erosion-prone areas and improving upon traditional RUSLE-based approaches. Rainfall erosivity ranges from 1520 to 1837 MJ mm/ha/h/yr, soil erodibility from 0.10 to 0.68 t ha hr/ha MJ mm, and the topographic factor from 0 to 353.3. Cover management and support practice values range between 0.74–1.07 and 0.1–0.9. Soil erosion rates in the river basin range from 0 to 50 t/ha/year, with an average rate of 2.42 t/ha/year. Low erosion (<1 t/ha/year) is predominant in alluvial plains and forested regions, while higher rates occur in uplands. Spatial analysis shows that 23.81 km2 experiences tolerant erosion, 10.65 km2 low erosion, and 0.49 km2 moderate erosion. Soil erosion hotspots with rates of 15–20 t/ha/year and 20–50 t/ha/year cover 0.1089 km2 and 0.1125 km2, respectively. The mean sediment yield is estimated at 1.635 t/ha/year, contributing to sedimentation in riverbeds and lowland areas. The RUSLE-SY model provides a high-resolution, spatially explicit assessment of soil loss and sediment yield. This study offers new insights into erosion dynamics within the ecologically sensitive tropical watershed of the Western Ghats, supporting regional conservation planning and sustainable land management strategies