Electrical Resistivity Tomography (ERT) for the Investigation of Erosion site in Oredide Village, Auchi in Etsako West LGA of Edo State, Southern Nigeria

Abstract

The Dipole –Dipole array was used for Constant Separation Traversing (CST) to investigate subsurface lithology in Oredide village, Auchi, Edo state with a view to determining the vulnerability or otherwise of the menace of erosion in the area. All the traverses were carried out with electrode spacing of 10 m with a spread of 200 m. The data was obtained using Pasi terrameter (16-GL) and processed with the Dipro software. The results revealed that the subsurface is underlain by the topsoil, lateritic sand, sand and sandstone. 2D results indicate topsoil with resistivity value range of 309 to 40130 Ωm within the depth range of 0 to 5 m. The second layer corresponds to sandy, lateritic sand, sand and sandstone  having resistivity values ranging from 2186 to 60350 Ωm to a depth of 10.0 m. The third layer has resistivity values  indicating lateritic sand, sand and sandstone layer with resistivity values ranging from 2186 to 60350 within the depth of  20 m. The fourth layer connotes lateritic sand, sand and sandstone to a depth of 30 m. The fifth horizon has resistivity values in the range of 585.2 to 35732.4 Ωm which is representative of sand and sandstone.The maximum depth imaged  was 47.7 m.The inverted 2-D resistivity structure shows high resistivity distribution near-surface >1000 Ωm, which are  indications of vulnerabilities to erosion in the study area with depth of scouring being 15 m.