Geophysical and hydrogeological evaluation of rising groundwater level in the coastal areas of Lagos, Nigeria

Abstract

The paper reports the change in groundwater level observed in 30 wells in ten locations in southern Nigeria. Borehole data confirmed the electrical resistivity soundings which indicated the presence of topsoil, medium sand, sand, clayey sand and coarse sand. In some cases, there was little apparent change in the rate of groundwater rise, but from the data obtained it can be concluded that in the years 2000–2004 the average yearly rise was 0.3 m while between 2004 and 2007 it rose on average by 0.5 m. This rise in groundwater level has serious implications for both existing structures and the nature of the foundations for future building. The electrical resistivity survey was found to be a helpful tool in detailing the morphology of the groundwater surface and is recommended for ongoing monitoring.