Appraisal Of Flood-Prone Litho-Stratigraphic Units Via Geo-Electrical Technology

Geo-electrostratigraphic assessments of flood-laden lithological units within a coastal region in Southern Nigeria were undertaken with the use of geophysical surveys. The region has challenges of extreme flooding, especially during periods of high precipitation, leading to intensive water-logging and its associated problems. Integrated surveys employing vertical electrical soundings and electrical resistivity tomography were undertaken at twenty locations with the use of Schlumberger and Wenner array configurations. Hydro-geophysical findings indicate that the region comprises comprises four of four geo-electric layers: motley topsoil, sandy clay, fine sand, and coarse sand. Interpretation of the geo-stratigraphic data delineated degrees of geo-anisotropy based on measures of the longitudinal conductance, transverse resistance, longitudinal conductivity, transverse conductivity, anisotropic co-efficient, and the reflection coefficient. Via use of Dar-Zarrouk parameters, the water retention capacity assessments show that the region has a generally good retentive capacity, leading to an increased susceptibility to extreme flooding. Results obtained from 2D resistivity tomography surveys corroborated the results obtained from vertical electrical sounding data interpretations. The results showed that area is highly anisotropic, and that the presence of argillaceous sequences intercalated with arenaceous stratigraphic units is the leading cause of the high water retentive capacity of the region, leading to flooding during periods of high precipitation.