Effect of urbanization, waste disposal and hydrological factors on flooding of Ogunpa stream in Nigeria

The Ogunpa is a major stream that passes through the thickly populated industrial and residential parts of Ibadan City, Nigeria. It is about 15 km long and empties into the Ona River. The Ogunpa first attracted attention in 1980, when an intense storm resulted in heavy flooding. However, it was not until 1988, following another flood in the wake of a relatively mild storm, that the Ogun-Oshun River Basin Development Authority (OORBDA) installed gauging stations for the flood-prone stream. The present article examines the effects of rainfall, urbanization and waste disposal habits on the flooding of the Ogunpa stream. A statistical analysis of daily stage readings for 1988 and 1989 at three gauging statons along the stream shows that these are periodic, that rainfall depths of 60 mm and above could lead to flood events, and that bad waste disposal habits are the main cause of flooding, especially at downstream subreach. Current efforts to channelize the stream may not completely reduce the incidence of flooding unless waste dumping and extensive urbanization of the flood plains are checked. Bibliogr., sum. in English and French.