Geophysical Evaluation of Erosion Sites in some Parts of Abia State, Southeastern Nigeria

Abstract

This work evaluates the external and internal structures of erosion sites in parts of Abia state, Nigeria and determines the gully erosion sensitivity of the sediments. Attributes such as lithology, land use, geomorphology, and climate were factored-in as gully erosion predisposing factors. The geophysical method used was the electrical method which employed the Schlumberger electrode configuration with maximum half current electrode spacing of AB/2 = 150 m, and 8 vertical electrical sounding (VES) data were acquired. The computer-aided resist software method was used for further processing and interpretation of the VES data. Thereafter some geo-electrical sections were drawn and hence the geologic units of the area obtained. Results show that the resistivity of the erosive materials range between 812.0 Ωm-3,738 Ωm, while the depth ranges from 16.6 m (VES 3) to 90.7 m (VES 6).  A correction factor was used in determining the true thickness of sediments where surface resistivity sounding data were acquired. The method depicts a valuable tool for assessing depth, thickness and nature of erosive material.