GIS-based assessment of regional environmental drivers of soil erosion risks in Isuikwuato, southeastern Nigeria

This study applied a modified CORINE–AHP (Analytic Hierarchy Process) framework within a GIS environment to assess soil erosion risk at Isuikwuato in southeastern Nigeria. The model integrated five environmental variables, rainfall erosivity, slope, soil erodibility, lithology, and land use/cover; weighted using expert-derived AHP criteria (CR = 0.06). Rainfall erosivity (weight = 0.35) and slope (0.30) emerged as dominant drivers, followed by soil erodibility (0.20), land cover (0.10), and lithology (0.05). The modified model replaced the traditional CORINE stoniness parameter with lithology to improve performance in tropical sedimentary settings. Results indicated that approximately 52.45% of the region wass moderately to highly susceptible to erosion, while 8.38% constituted non-resistant zones that aligned with steep slopes and drainage corridors. Model validation, using 27 field-mapped gullies, produced an AUC of 0.82 and a spatial correlation (r = 0.91), confirming reasonable predictive accuracy. Spatial transition analysis revealed a 5.73% decline in 'highly resistant zones' and a 2.48% increase in 'non-resistant' areas, underscoring active landscape degradation. The findings align with regional patterns across southeastern Nigeria and elsewhere , where high rainfall erosivity and steep topography are dominant erosive factors. The methodology of composite climatic indices (MFI–BGI) and lithological substitution enhanced the CORINE model’s applicability to the study area, as typical of tropical conditions. The study concluded that the modified CORINE-AHP model is capable of providing a decision-support information for erosion-risk mapping and land management planning in data-limited sedimentary terrains.