Geological Behavior (GBR)

An integrated electrostratigraphic investigation was conducted to assess the intrinsic vulnerability of the coastal aquifer at the Federal College of Education, Omoku, Rivers State. Twenty Vertical Electrical Sounding (VES) stations were employed, revealing a heterogeneous subsurface composed of four distinct geoelectric layers. The resistivity and thickness of the topsoil and unsaturated vadose zone were identified as the primary controls on vulnerability. The study utilized three vulnerability models: GOD, GLSI, and DRASTIC. The GOD index classified the area into low (33.3%) and moderate (66.7%) vulnerability classes. In contrast, the GLSI index, derived directly from VES data, provided a higher-resolution assessment, identifying two high-risk points (10%), a majority of moderate vulnerability (80%), and two low-vulnerability points (10%). The DRASTIC model consistently rated the entire area as moderately vulnerable, reflecting the inherent risk of the coastal hydrogeological setting. The comparative analysis concluded that the aquifer system is predominantly moderately vulnerable with localized zones of high vulnerability, particularly where protective layers are thin and conductive. The GLSI model proved most sensitive for pinpointing these high￾risk areas. The findings underscore the urgent need for targeted groundwater protection strategies, land-use regulations, and continuous monitoring in the identified vulnerable zones to ensure sustainable water resource management in this coastal environment.