FLOOD RISK AND VULNERABILITY ASSESSMENT OF KADUNA RIVER, NIGERIAE. O. Iguisi (1), D. N. Jeb (2) River Kaduna flows through the city of Kaduna, northern Nigeria. In the recent decades shortly after Nigeria attained Independence from Great Britain, the City has been experiencing tremendous expansion. The growth of the City can be attributed to the elevated status of the City becoming a regional administrative and commerciial centre in northen Nigeria which consequently led to a dramatic influx of large number of people into the city for jobs, education, medicare,etc. The process of uncontrolled urbanization thus led to the enchroachment of built-up areas into the flood plains of the river. Recent climatic data shows that rainfall within this region is on the increase with greater intensity. Runoff coefficient within the City is also on the increase due to substantial increases in paved surfaces. Progressive defforestation, intensive cultivation, overgrazing and other unwholesome landuse practices are also widely reported within the drainage basin of the river. These factors collectively predisposes the river to flooding. If a major flood occurs along the course of this river several lives and properties are most likely to be lost. This study is, therefore, aimed at assessing the risks and vulnerabilities of such a flood, if it happens. A combination of field studies and Geographical Information System technique were used for the study. Three flood inundation scenerios were created along the corridor of the river course within the City.These are the corridors of: (i) 100 m on both sides of the river, (ii) 300 m on both sides of the river, and (iii) 500 m on both sides of the river. Various magnitudes of flood were also modelled for the river course, based on historical records of river stage. These corridors were subset from large scale satellite imagery of the city for analysis. Properties and facilities which are likely to be affected by flood of various magnitudes were digitized using Arcgis software. Population likely to be affected by various magnitudes of flood were also calculated, using data obtained from the Federal Population Commission and household survey. Results obtained from the various analyses indicate that:(i) A low magnitude flood will completely inundate every house, farm, facility, man and livestock within the vicinity of 300 m on both sides of the river. A major flood will take out every structure within the 500 m corridor. The implication of this result is that unless urgent mitigation measures are put in place, post damage loss assessment may indicate billions of dollars of properties and thousands of lives lost to river Kaduna flood disaster. |
