Earth Science Malaysia (ESMY)

This research work assessed the gully erosion susceptibility of Ikwuano Local Government Area of Abia State, Nigeria using the GIS-based multi-criteria evaluation approach. The objectives were to identify susceptible areas, examine and evaluate the causes as well as the impacts and recommend possible control measures. The multi-criteria evaluation approach of pairwise comparison by Analytical Hierarchy Process was used to calculate and assign criteria weights to the 5 erosion factors. The pairwise comparison matrix was tested using Saaty Consistency Ratio to ensure accuracy. The five erosion controlling factors were analyzed in the GIS environment and prioritized as rainfall erosivity (R factor, 36%), soil erodibility (K factor, 30%), slope (LS factor, 19%), vegetative cover (C factor, 9%) and conservation practice (P factor, 6%) in order of importance. The susceptibility map was produced and validated by ground truthing. Gully initiations are widespread in the study area. Dormant gullies at Umulu, Ihim and Amuro are well-vegetated with bambusa vulgaris. The active gullies at Elemaga-Ibere and Amaegbu-Ariam are within the moderate to high susceptible areas. The major anthropogenic causes of erosion in the study area include sand mining, bad farming practices, lumbering, poor drainage system and abandoned road constructions. The impacts included the destruction of roads and houses, isolation of communities, loss of farmlands and silting of streams. Tree planting and regrassing, engineering and structural designs to channel runoff, proper road design, improved farming practices and engaging in sensitization of all stakeholders targeted on early stage preventive measures were recommended. The GIS-based multi-criteria evaluation approach has proved both useful and effective in the mapping of gully erosion susceptibility in Ikwuano Local Government Area of Abia State, Nigeria.