Assessment of Flood Causative Factors Using GIS-Based Multi-Criteria Analysis for Flood Hazard and Risk Mapping in Calabar South, Nigeria

Flooding remains a persistent environmental hazard in coastal urban areas of southern Nigeria, particularly in Calabar South Local Government Area, where low elevation, intense rainfall, and rapid urbanization exacerbate flood impacts. This study assesses flood causative factors and delineates flood hazard and risk zones using an integrated GIS-based Multi-Criteria Analysis (MCA) framework. Five flood conditioning factors; elevation, slope, flow accumulation, rainfall intensity, and land use/land cover, were derived from SRTM Digital Elevation Model, Landsat imagery, and meteorological datasets. Factor weights were objectively determined using the Analytic Hierarchy Process (AHP), and spatial integration was performed through a weighted linear combination approach in ArcGIS. Flood risk assessment was conducted by integrating flood hazard with population density and land use exposure. Results indicate that approximately 58.6% of Calabar South falls within high to very high flood hazard zones, largely concentrated in low-lying southern areas. Flood risk analysis reveals that 35.9% of the study area is exposed to high to very high flood risk, driven by the coincidence of intense hazard conditions and dense urban development. Elevation and slope emerged as the dominant flood causative factors, while urban land use significantly amplifies flood risk. The generated flood hazard and risk maps provide reliable spatial decision-support tools for flood mitigation planning, land-use regulation, and disaster risk management in coastal urban environments.