Soil Erosion Modelling and Conservation Planning in the Upper Anambra River Catchment

The upper Anambra River catchment spanning portions of Anambra and Enugu states in South East Nigeria is characterised by highly erodible Tertiary sands and degraded agricultural land that generate excessive sediment loads threatening downstream water infrastructure and agricultural productivity. This study models soil erosion rates and develops a conservation plan for the upper Anambra River catchment using the Revised Universal Soil Loss Equation implemented within a GIS environment. Rainfall erosivity was computed from daily rainfall data spanning twenty years from meteorological stations within and adjacent to the catchment using the Fournier index. Soil erodibility factors were assigned from published look-up tables for dominant soil series in the catchment validated by independent sediment trap data. Slope length and steepness factors were derived from a ten-metre resolution digital elevation model. Cover management and conservation practice factors were assigned based on land cover classification from Sentinel-2 imagery. The resulting annual soil loss map was classified into erosion severity categories aligned with the Food and Agriculture Organisation erosion risk framework. Priority conservation zones are identified where estimated annual soil loss exceeds the tolerable soil loss threshold. Conservation interventions including vetiver grass strips, terracing, and agroforestry are evaluated for feasibility using a cost-benefit analysis. Recommendations are submitted to the Anambra State Agricultural Development Programme. Keywords: soil erosion modelling, RUSLE, Anambra River catchment, conservation planning, GIS.