Vertical Electrical Sounding (VES. Investigation of Aquifer and Potential Clay Materials in Douala Subbasin (Cameroon, Central Africa)

Abstract

Vertical electrical sounding was done at 47 points using an ABEM 1000 Terrameter and a set of cables that could probe up to a depth of 500m. Resistivity was determined in two sites located in the district of Douala III (Bomkoul and Ngoma) 6 km west of the main town on the left bank of the Wouri River. The choice of these neighbourhood is as a result on the one hand, the presence of clay deposits from which sections have helped to configure resistivity data with those of geoelectric sections, and on the other hand, by the ability to extend the measuring device over great distances without being hindered by urbanization. The depths of investigation range from a minimum of 30 m and a maximum of 120 m. The results show a wide variability in resistivity values throughout the study area; it may be related to the high variability of facies described on sections by diggers. This variability may be due to the complexity of deposits recorded in the Douala sedimentary basin and also because of the presence of water in both sandy and clay sediments due to climate. The suggested resistivity is between 20 and 600ohm.m for clays and greater than 1000 ohm.m for sand. Given the weak thickness of some layers, the cancellation phenomena that affect very thin layers between two layers of different geoelectric properties of the latter have been observed, thus assigning to clay layers, sand resistivity.

Morpho-Structural Mapping Constraints from Geophysical and Test Pit Investigations: Case Study of the Bomkoul Locality in Douala Sedimentary Basin, Cameroon, Central Africa

“…Those of weak resistivities have planar bed flows with an average hydrodynamic deposit process. Planar bed flows with an average hydrodynamic deposit process had been identified by (Mbog et al, 2016). The almost constant resistivity values between 1 and 2 m depth could indicate homogenization of the soil with an intrusion around the S9 station (Figure 3(b)) which is more extensive between the surface and 1 m deep (Figure 3(a)).…”