Morphological Adjustment of a Tropical River to Urbanization
Mogborukor J.O.A

Abstract
The work examined how stream channel morphological characteristics and hydraulic variables responses are significantly related to different parameters of urban land use practices in Orogodo River. A threefold research strategy was adopted. The first step involved demarcating the river long profile into ten (10) sites of 10km of the urbanized section as study area. This was done in order to obtain information on stream channel bank full cross sectional areas, basin morphometry and urban land use characteristics. Secondly, the chosen sites (10km) were detailed for measurement of stream hydraulic variables. Data on land use were obtained from systematic examination of topographic and land use maps of Agbor, 2009. Thirteen (13), urban land use and morphometric variables that are related to stream channel adjustment were factor analyzed. Three independent variables made up of amount of rain fall, volume of drainage discharge and infiltration capacity of the soil were statistically significant in explaining stream channel morphological characteristics. From the study, it is clear that prolonged engagement of urban land use to construction and creation of impervious surfaces will continue to cause stream channel to adjust to the changing run off and sediment yield such that over the years stream channel sizes are enlarged. It is therefore recommended that an integrated programme of basin land use and structural alternatives will include the development of green belts/lawns and other options that encourage high level of infiltration rather than the development of storm sewers. It is also recommended that, an approach of rain water harvesting should be encouraged within the river basin. If adopted by the inhabitants, it will reduce peak flow into river channel.

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