Geophysical Hazard Zonation for Infrastructure Planning Along the Lokoja-Abuja Highway Corridor, North Central Nigeria

The Lokoja-Abuja highway is a critical national artery connecting Kogi, Niger, and Kaduna states, and geotechnical hazards including rockfall, landslide, and expansive soil failure have been documented along several sections, requiring systematic geophysical hazard zonation to support road widening and maintenance planning. This professional study conducts a geophysical hazard assessment along a 120-kilometre section of the highway from Lokoja to Abuja using a combination of electrical resistivity profiling, seismic refraction, and ground magnetic surveys at identified problem sections. Fifteen problem sections identified from road condition surveys were prioritised for detailed geophysical investigation. ERT and seismic refraction were conducted at each problem section, while ground magnetic traverses were used to identify buried structural features such as dyke intrusives or fault zones that can be associated with sudden changes in rock mass quality. Results indicate that 7 of the 15 problem sections are characterised by deeply weathered basement profiles where soil moisture variability during wet and dry seasons drives volume change in expansive soils, leading to pavement heave and cracking. Four sections are identified as rockfall-prone based on high-velocity refraction arrivals within 1 metre of the cut slope face, indicating fresh competent rock susceptible to joint-controlled block toppling. The integrated hazard zonation map classifies each section into low, moderate, high, and very high hazard categories. Mitigation recommendations are provided for each hazard type. Keywords: geophysical hazard, highway, Lokoja-Abuja, expansive soils, rockfall