Soil erosion is a critical environmental concern that undermines agricultural productivity, water quality, and land sustainability, particularly in monsoon-dominated semi-arid regions. This study assesses the spatial distribution and severity of soil erosion in the Thamirabarani River Basin (TRB), located in southern India, using the Revised Universal Soil Loss Equation (RUSLE) integrated with Geographic Information Systems (GIS) and remote sensing techniques. The primary objective is to quantify soil erosion rates and analyse the influence of rainfall and vegetation cover (derived from NDVI) over 23 years (2000-2023). High-resolution Landsat 9, SRTM DEM, rainfall data from the Indian Meteorological Department, and Soil and land use information were used to derive the RUSLE factors. Results show that annual soil erosion ranges from < 0.4 to 10.8 tons/ha/year, with higher erosion in pediplains, barrens, and sloped channel paths, while forested and irrigated zones exhibit lower rates. A clear spatial correlation between low NDVI, high rainfall intensity, and elevated erosion rates was observed. The RUSLE model output was validated using 40 geolocated erosion points from Google Earth imagery, yielding an AUC value of 0.823, indicating reliable performance. The study highlights erosion hotspots and recommends targeted conservation measures such as afforestation, contour ploughing, and check dams. The findings provide a spatially explicit erosion risk map, essential for sustainable watershed management and planning, as well as climate-resilient soil conservation strategies in the TRB.