Flow Simulation of River Omi, Ibadan, Nigeria, Using Average Proportionality and Linear Regression Methods

Omi river flows through Omi-Adio, Iddo Local Government Area (LGA) of Oyo State, Nigeria. The watershed hydrology of the river, over the years, has changed considerably due to the ever increasing anthropogenic activities. The resultant effect is the inundation of farmlands and flooding of residential areas in Omi-Adio township, whenever the river overflowed after heavy rain falls. Unfortunately, as with most Nigerian rivers, no discharge record exists for Omi river, making planning for provision of hydraulic structures difficult. One hundred and three years of available rainfall data and existing five years of discharge record for Ogunpa river at Molete grammar school were used to simulate surface runoff for Omi river, using average proportionality and linear regression methods. The approximation of data was based on established literature, which states that Omi and Ogunpa Rivers have similar geological and morphological characteristics. The simulation was validated with field measurements. The constant of proportionality between the two rivers was found to be 2.467. The constants: 'a' and 'b' in the linear regression equation for Omi River were computed to be 0.306445 and 0.0003036, respectively, with a correlation coefficient of 0.98876. The linear regression method was found to be more appropriate for Omi River at Omi Adio, Ibadan, when compared with field values. The study will assist in providing reasonable data in the design of hydraulic structures such as bridges, concrete channels, culverts and flood control structures for Omi-Adio LGA.