Flood Reduction through Flood Risk and Vulnerability Assessment and Mapping in Hadejia River Basin, Nigeria
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Floods are one of the most recurrent and devastating natural disasters that has enormous, widespread and ravaging negative impacts on lives, economy and infrastructures across the globe. Hadejia River Basin is known by its frequent flood occurrences which claims many lives and destroyed several infrastructures and vast hectares of farmlands. The purpose of this research was to develop a GIS-based flood risk and vulnerability mapping integrated with Analytical Hierarchical Process (AHP) in order to reduce the risk and vulnerabilities associated with flood in Hadejia River Basin. The research employs an efficient and reliable methodology in preparing flood risk map for the Hadejia River Basin based on the concepts of integration of flood hazard and socioeconomic vulnerability indicators. The risk map of the basin was generated by aggregating the geomorphological, hydrological, and socio-economic indicators namely; elevation, mean annual rainfall, slope, distance to rivers, soil type, drainage density, population density, female population density, literacy rate, land-use, and employment rate and road network in GIS framework using multi-criteria analysis technique called the Analytical Hierarchy Process (AHP). Accordingly, the northeastern and southeastern parts of the study area are prone to frequent floods which constitutes very high and high flood hazard zones of about 10.4% (3179.1 Km2) and 17.2% (5257.8 Km2) of the watershed while vulnerabilities levels are higher at the southeastern, central and extreme upstream parts of the study area which covers about 24.1% (7367Km2) of the study area. Moreover, combination of the flood hazard (FHI) and vulnerability (FVI) indices of Hadejia River Basin reveals about 43.4% of the basin is under high and very high flood risk covering about 13266.8Km2. The study also reveals that flood hazard and vulnerability indicators have different influence to flood risk. Furthermore, the results are validated and found to be in agreement with the historical records of flood distribution of the study area. This proves the reliability and applicability of the proposed methodology. This research has significant importance in developing strategic measures and plans through which government and relief agencies will reduce and/or prevent the negative impact of flood risk and socioeconomic vulnerability in the Hadejia River Basin.