GIS-BASED MULTI-CRITERIA DECISION ANALYSIS FOR FLOOD RISK ASSESSMENT AND MITIGATION IN URBANIZING AREAS: A CASE STUDY OF ILORIN WEST, NIGERIA

Abstract

This study addresses flood vulnerability in the rapidly urbanizing Ilorin West Local Government Area, Nigeria, through a GIS-based Multi-Criteria Decision Analysis (MCDA) approach for flood risk assessment and mitigation. Integrating key spatial factors, including distance from river channels, rainfall intensity, elevation, slope, and land use/land cover, MCDA employs a weighted overlay technique to generate a detailed flood susceptibility map. The Analytical Hierarchy Process (AHP) was utilized to assign objective weights to each criterion based on expert judgment, ensuring the robust prioritization of flood risk factors. The resulting map classifies the area into four risk categories: very high, high, moderate, and low. Findings show that 1.8% of the area, encompassing neighborhoods like Alanamu and Oloje, falls under very high flood risk, while 35.6% and 26.6% are categorized as high and moderate risk, respectively. Flood vulnerability is predominantly concentrated in low-lying riverside communities characterized by impervious surfaces and inadequate drainage. This research demonstrates the effectiveness of GIS-based MCDA as a decision-support tool for urban planners, emergency responders, and policymakers in flood risk mitigation and sustainable urban development. The study’s outcomes align with Sustainable Development Goals 11 and 13, offering a replicable framework for flood risk management in urbanizing regions across sub-Saharan Africa.