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Flood Risk Assessment of Port Harcourt, Rivers State, Nigeria

K. C. Chiadikobi, A. O. Omoboriowo, O. I. Chiaghanam, A.O. Opatola and O. Oyebanji

The rapid rates of urbanization and population growth of Port Harcourt city in the last ten years have led to uncontrolled and uncoordinated development of swamps, floodplains and natural drainage channels thereby aggravating the risk of flood hazards in the city. This study examined the flood risk in Port Harcourt using rainfall data, soil texture and other factors. The proportions of clay slit and sand particles in the soils were determined. Permeability result obtained is within the range of low-very low permeability (10-4 – 10-6 cm/sec). Years with high rainfall events which correspond to years of high flood risk in Port Harcourt include 1998, 2000, 2002, 2003, 2004, 2006 and 2007. The percentages of rain events with high intensities in these years are; 39.4%, 52.7%, 32.7%, 40%, 35.8%, and 44.6% respectively. Rainfall intensity obtained is within the range of 53.8 – 20.4% for high to low intensities. Rainfall intensity is high in Port Harcourt due to climatic changes such as high rainfall volume and duration. The result of this study shows that the risk of the occurrence of potentially damaging flood in Port Harcourt increases with increasing rainfall intensity. Also, the risk of flood is bound to increase in the future with increasing urbanization hence the need to demarcate the flooded areas for effective flood mitigation.