Landslide Susceptibility Assessment in a Basement Environment using Slope and Geoelectric Parameters: Case Study of Adebowale Area, Akure Southwestern Nigeria

Abstract

The assessment of landslide susceptibility was carried out at Adebowale community in Akure South Local Government Area of Ondo  State, Nigeria. A total of (60) sixty Vertical Electrical Sounding (VES) data were acquired using Schlumberger electrode configuration with  a maximum half-current electrode separation (AB/2) of 150 - 225 m. The Vertical Electrical Sounding (VES) results were presented as maps  and tables. The VES results delineated three to five geoelectric layers across the study area. The A, H, K, HA, KH, AKH and HKH are  the seven sounding curve types delineated in the area. The resistivity of the topsoil, clayey sand weathered layer, sandy clayey weathered  layer and weathered bedrock/fresh bedrock varies from 24 to 961 Ωm, 13 to 4141 Ωm, 24 to 72739 Ωm and 122 to 100000 Ωm  respectively. Four parameters of importance to landslide were used to develop a landslide susceptibility model for the study. The  parameters consisted of slope, topsoil resistivity, weathered layer resistivity, and longitudinal resistivity. These parameters or factors  were assigned weights and ratings based on their significance to the landslide. A landslide susceptibility map (LSSM) was produced using  the determined landslide susceptibility index. The LSSM classified the area into five landslide susceptibility zones; very low, low,  moderate, high and very high respectively. The model was able to predict areas with very low susceptibility, low susceptibility, moderate susceptibility, high susceptibility and very high susceptibility within the study area. The northern pocket of the southwestern part of the  study area revealed very low to low landslide susceptibility while the southwestern and north-central parts of the map are of moderate to  very high landslide susceptibility.