Urban Flood Risk Information on a River Catchment in a Part of Ilorin Metropolis, Kwara State. Nigeria

Abstract

This study identifies areas at risk to urban flood along Aluko river channel in Ilorin and provides information on flood risk implications on the city dwellers. Data sets on roads, river, dump sites and contour lines were extracted from Ikonos Imagery and Topographical map of Ilorin. The study area was demarcated as high, moderate and low flood risk zones, based on approved setbacks and previous flood extent. Buffering, Overlay Operations, Digital Terrain Modeling, Flow Accumulation and Spatial Search were the spatial analyses carried out using ArcGis 9.3b. The digital terrain model revealed that the study area is situated on near uniform lowland, with the vulnerable zones located on the deepest part of the plain, and this is responsible for the high flood vulnerability of this area. Flow accumulation spots, coupled with refuse dumps were identified as key factors that heighten the level of flood susceptibility in the area. About 288 buildings contravene the setback rule and a total of 10,820 people were estimated to be at risk of urban flood in the three zones. The study recommends adoption of Geographic information system for policy formulation and decisions making on planning, regulation and development along streams in urban centers.

Key words: flood, Geographic Information, spatial analysis, vulnerable, flood risk