FLOOD HAZARD MAPPING OF THE LOWER BENUE RIVER BASIN

Abstract Flooding is a recurrent and intensifying hazard in West Africa, exacerbated by climate variability, land use change, and limited flood management infrastructure. This study assesses flood hazard dynamics in the Lower Benue River Basin (LBRB), Nigeria, through the integration of Sentinel-1 Synthetic Aperture Radar (SAR) imagery and land use/land cover (LULC) data between June and November 2022. Using Google Earth Engine (GEE), multi-temporal SAR data were pre-processed and classified employing Random Forest, K-Nearest Neighbours, and Maximum Likelihood algorithms to detect and map flood extents. October 2022 was identified as the peak flood month, with an inundated area of approximately 145 km². Spatial analysis revealed that croplands (75.5% inundated), wetlands (100%), and built-up areas (67.7%) were most exposed. Site-specific assessments in Makurdi, Gbajimba, Loko, and Oguma highlighted varying flood impacts driven by topography, land cover patterns, and settlement expansion. Results underscore the urgency of floodplain zoning, nature-based mitigation strategies, and early warning systems. This study demonstrates the applicability of SAR-based flood monitoring in data-scarce regions and provides a replicable framework for hazard assessment and disaster preparedness in tropical basins.