Flood occurrence and adjustment strategies in Oyo State: a case study of Ogunpa drainage basin
Floods are among the most dramatic forms of interaction between man and his environment, and they emphasize the limitations of man in his attempt to control the sheer force of nature. When they occur, whether in the developed or the developing world, they are always associated with heavy losses of life and property, misery, hardship disease and at times, famine. The Third Order Rivers, the Ogunpa and Kudeti, do break their banks so frequently that flooding in the arrears has been described as the lbadan Annual Festival. It has been observed that flood occurrence has been aggravated by the deplorable habit of indiscriminate dumping of refuse by people, who have encroached on the floodplain and also waste dumping by ubiquitous street traders, which blocked the drains. The accumulation of wastes and debris increases the roughness of the channel and thereby reduces the hydraulic capacity. This affects the dogging of the culverts and bridges. It was also observed that construction of buildings, roads and bridges were made adjacent to the river channels, occupying the areas where the flood could flow to and obstructing the floodplain and the flood paths. Channel construction is an issue that should be carefully examined by policy and decision makers in our society. This paper therefore identifies that flood menace could be an hindrance to national development and therefore recommends that a collaborative effort by fluvial geo-morpbologists, hydrologists, engineers, waste management authorities, planners and politicians should be embraced so as to effectively manage flood risks in Oyo State and the Nation at large.
Keywords: Floods, Third Order Rivers, hydraulic capacity, channelization, channel construction, debris.