Soil Erodibility and Erosion Risk Assessment Using RUSLE and Remote Sensing in Anambra-Imo River Basin, South East Nigeria

This study assesses soil erodibility and estimates erosion risk across the Anambra-Imo River Basin using the Revised Universal Soil Loss Equation (RUSLE) integrated with remote sensing and geographic information system analysis, addressing a basin-level spatial gap in erosion quantification for the most severely eroded river catchment in South East Nigeria. The Anambra-Imo Basin spans parts of Anambra, Imo, and Enugu States and contains the largest concentration of active gullies in Nigeria, yet a basin-scale spatially continuous erosion risk assessment using current remote sensing data has not been published. Using a GIS-integrated RUSLE approach, all five RUSLE factors (R, K, LS, C, P) were derived from spatially distributed data sources: 35-year rainfall data from six NIMET stations (R), laboratory-derived K-factors from 45 representative soil samples (K), SRTM DEM topographic analysis (LS), Sentinel-2 land cover classification (C), and field-verified conservation practice inventory (P). Annual soil loss estimates were calculated at 30-metre resolution and validated against measured sediment yield data from three gauged catchments within the basin. Findings revealed that high-erosion zones (greater than 100 tonnes per hectare per year) covered approximately 9.4 percent of the basin area, concentrated in the east-facing scarps and dissected terrain of Imo and Anambra States. The C-factor showed the greatest variation, reflecting the dominant role of vegetation cover management in controlling erosion within the basin. Validation showed 76 percent agreement with measured catchment sediment yields. The study provides actionable erosion risk data for prioritising basin-level soil conservation investment. Keywords: RUSLE, soil erodibility, Anambra-Imo River Basin, GIS, erosion risk assessment.