ASSESSING GEOMORPHODYNAMIC IMPACTS OF GULLY EROSION IN SOUTHERN GOMBE STATE, NIGERIA

Abstract

Gully erosion poses a significant environmental threat in Southern Gombe State, Nigeria, yet assessments and interventions have remained geographically restricted despite widespread devastation. This study assessed the geomorphodynamic impacts of gully erosion across seven local government areas, employing field surveys and morphometric measurements of 130 permanent gully sites. Results revealed three gully types: continuous (35%), discontinuous (55%), and bank (10%), affecting 34,499.2 hectares (4.3% of the study area). Continuous gullies occupied the largest area (64%) due to favorable conditions including large drainage basins and deep soils, while discontinuous gullies, though numerically superior, covered only 11% of affected land. Gully dimensions were severe, with depths reaching 20m, lengths exceeding 10km, and widths up to 68m. Distinct geomorphodynamic processes operated across LGAs: drainage capture and sediment deposition in Akko; channel widening and high sediment yield in Balanga; mass wasting in Billiri; slope undercutting in Gombe; headward retreat in Kaltungo; network expansion in Shongom; and wall slumping in Yamaltu-Deba. These processes have converted productive agricultural land into dissected terrain, threatening food security, infrastructure, and livelihoods in this agrarian region. The study concludes that current engineering-dominated interventions are inadequate, frequently failing within 2-3 years, and recommends integrated, process-based approaches that work with natural geomorphological dynamics rather than against them. LGA-specific strategies including sediment trapping, vegetative stabilization, and improved drainage management are proposed to address the varying erosion mechanisms across the region.