Flood Susceptibility Mapping in Asa Local Government Area, Kwara State, using Remote Sensing and GIS Approach

Abstract

Abstract: The increasing incidences of flood events in recent times have necessitated the need to come up with an early warning information for flood risk preparedness and reduction. The study aimed at mapping flood susceptibility in Asa Local Government Area, Kwara State, using Geographic Information System (GIS) based multi criteria evaluation approach. The data required for the study include: rainfall amount, soil texture, digital elevation model, distance from stream (euclidean distance) and land use land cover of the study area. Using Analytic Hierarchical Process, flood criteria weights were calculated for the different variables according to their influence on flooding and overlay analysis was employed in analysing the data for the study. The result of the study show there is spatial variation in the level of susceptibility to flood risks in the study area. Thus, the low-risk area covers 16.1% (~222.24 km2 ), moderate class 28.8% (~398.08 km2

), high risk zone occupies 39.5% (~408.70 km2 )

while the very high-risk zone takes up 25.6% (~354.15 km2

) of the area coverage of the study area. Furthermore, the accuracy assessment produced area under the curve (AUC) value of 0.795 (~80%). From the study, it was also discovered that Owode, parts of Afon, Bode, Onikangu, Abule-Alagbede fall within the very high and high-risk flood zones. The map could be a useful tool to decision makers in Asa local government for effective flood management plans.