Ground Penetrating Radar Investigation of Near-Surface Structures in Port Harcourt

This study applies ground penetrating radar to investigate near-surface structures, utility locations, and buried anomalies in selected areas of Port Harcourt, Rivers State, South South Nigeria. Urban infrastructure management in Port Harcourt is complicated by the presence of uncharted buried utilities, including water pipes, telecommunications cables, and drainage structures, that create engineering risks for road rehabilitation and construction projects. GPR provides a non-destructive, high-resolution imaging tool that can locate buried objects and map stratigraphic discontinuities in the shallow subsurface without the need for excavation. This study deploys a 400-megahertz shielded antenna connected to a MALA ProEx GPR system along transects in the GRA Phase 2 and Rumuola districts. Data are acquired in continuous mode with time windows of 80 nanoseconds and processed using standard GPR processing sequences in ReflexW software including DC removal, time-zero correction, bandpass filtering, gain correction, and topographic migration. Findings reveal numerous hyperbolic diffractions interpreted as metallic pipes, conduit cables, and PVC drainage lines at depths between 0.3 and 1.8 metres. A major reflector sequence at 1.2 to 2.4 metres depth corresponds to a basal sand layer beneath reclaimed fill material, consistent with the geotechnical conditions common in Port Harcourt's coastal environment. Three anomalous zones associated with suspected voids or disturbed fill require attention before road resurfacing. The study demonstrates that GPR is an effective urban subsurface mapping tool for Port Harcourt's infrastructure management challenges.

Keywords: ground penetrating radar, urban subsurface, buried utilities, Port Harcourt, near-surface imaging.