GIS-assisted Flood-risk Potential Mapping of Ilorin and its Environs, Kwara State, Nigeria

Abstract

The incessant reoccurrence of flooding disasters across Nigeria has mandated an urgent outlook on flood-risk management techniques. Ilorin and its environs have suffered immensely from annual flood reoccurrence. This study aims to assess flood risk within Ilorin and its environs and proffer adequate flood mitigation strategies that governments and policymakers can adopt to placate future flooding events within the state. Satellite imagery data were acquired and analyzed for flood-risk assessment of the area. Ten highly influential flood causative factors were synergized using Multi-Criteria Decision-Making techniques in this research; they are Land Surface Temperature, Elevation, Soil Moisture Index, and Distance to Stream, Drainage Density, Stream Power Index, Normalized Difference Vegetation Index, Land Use Land Cover, Slope, and Topographic Wetness Index. Findings showed that approximately 47.2% of the study area had low flood risk, while moderate and high flood-risk zones occupied 33.5% and 19.29%, respectively. Most parts of Ilorin and its environs are safe from flood disasters; only about one-quarter of the total area under investigation lies in the high flood-risk zones; these areas mostly fall within the shores of major streams, rivers, and dams within the state. A plot of previous flood cases in the state placed the affected areas in the high and moderate zones of flood risk, confirming the efficacy of geospatial techniques in flood-risk assessment. It is hoped that this study's findings and recommendations can be implemented to prevent future devastating flooding occurrences within the state.