Impact of Flood Susceptibility Mapping as an Early Warning Tool in a Changing Environment

Abstract

In this study, an attempt was made to develop a flood susceptibility map around Ikpoba catchment in Benin City, Nigeria. The communities within the study area include; Agemopa, Odighi, Okohuo, Aihuobabekun, Ogbogiobo, Evboneka, Izakagbo, Ekiadoro, Utekon, Igozula, Ada Obadan, Ogheghe, Uselu, Aho, Igueowieoba, Iguomo, Ugonoba and Oka. Others are; Uweyoba, Urhuokhokhor, Egbiri, Evbuomoma, Ugoneki, Utesi, Utezi and Obaretin community. Ten thematic maps namely; Topographic wetness index (TWI) map, Elevation map, Slope map, Precipitation map, Land use land cover map, Normalized difference vegetation index (NDVI) map, Distance from river map, Distance from road map, Drainage density map and soil map were employed for the study. The thematic maps were thereafter reclassified in order to obtain a uniform scale. To obtain the percentage weight of influence for each of the data, analytical hierarchy process (AHP) was employed to generate a pairwise comparison matrix which validated using the index of consistency. Thereafter weighted overlay method was employed to stack the reclassify maps in order to generate the final flood map. To determine the areas with high flood risk, the flood map was converted to kml file and thereafter projected to google. The outcome revealed that communities such as; Odighi and Okohuo pose a very high risk of flooding while Aihuobabekun, Ogbogiobo, Evboneka, Izakagbo, Ekiadoro, Ogheghe, Uselu and Aho pose a high risk of flooding.