Application of Remote Sensing and GIS for Soil Erosion Risk Mapping in Anambra State, South East Nigeria

This study demonstrates the application of remote sensing data and geographic information systems (GIS) for professional mapping of soil erosion risk in Anambra State, located in Nigeria's South East geopolitical zone. Anambra State is among the most severely erosion-affected states in Nigeria, and resource-efficient digital mapping tools are essential for planning targeted conservation investments across the state's complex terrain. Using a geospatial analytical methodology, the study integrated satellite imagery (Sentinel-2), SRTM digital elevation model data, rainfall erosivity values from interpolated NIMET datasets, and soil erodibility K-factors derived from representative profile analyses to compute the Revised Universal Soil Loss Equation (RUSLE) for the entire state at 30-metre spatial resolution. Land cover was classified from Sentinel-2 imagery to derive the vegetation and cover management factor (C-factor). Conservation support practice factor (P-factor) was assigned from field verification of actual conservation measures. Findings revealed that approximately 22 percent of Anambra State experienced very high to extreme estimated annual soil loss (greater than 50 tonnes per hectare per year), concentrated in the Mamu and Nkisi catchments. Areas of highest erosion risk corresponded to steep slopes under degraded land cover and bare or cultivated soils with minimal conservation measures. The GIS-derived erosion risk map was validated against field-observed gully density data with 84 percent spatial agreement. The study delivers a professional soil erosion risk map product and recommends its integration into the Anambra State Ministry of Environment's land management planning database. Keywords: soil erosion risk mapping, remote sensing, GIS, Anambra State, RUSLE.