Boundary Influence and Flow Characteristics of Orisa and Ala Rivers in Kwara and Ondo States, Nigeria

Abstract

In this study, the effects of boundary influence on flow characteristics of Rivers Ala and Orisa were investigated. Soil samples were  collected from three points each from both rivers namely Glory Parish Area (GPA), Olusola Oke Area (OOA) and Fiwasaye; Aran-Orin Area  (AOA), Rore and Omu-Aran on Rivers Ala and Orisa Respectively. A MGG/KL-DCB Portable Electromagnetic Velocity Meter was used to  measure the in-situ readings of discharge and velocity at the various points. The sediments collected from the sampling points were  placed in the Flume in the Hydraulic Laboratory of Civil Engineering Department, Landmark University. The Flume was then set with the  measured parameter (Discharge) for each sampling point to apply the Flume to determine the Velocity for both Rivers at slopes of 0.008  to 0.056 respectively. The velocities obtained at the different slopes were inserted into Manning’s Coefficient equation to obtain the flow  characteristics. The relationship between the velocity and Manning’s Coefficient was determined using the Spearman's rank correlation  coefficient. All analyses were done at P-value less than 0.05 level of significance. The velocity varied between 0.0237+ 0.0004 and 0.0587+  0.0004 m/s; 0.0542+ 0.0004 and 0.0701+ 0.0003m/s and 0.0789+ 0.0005 and 0.0172+ 0.1323m/s for GPA, OOA and Fiwasaye for Ala River  and between 0.0751+ 0.0007 and 0.1008+ 0.0006m/s; 0.0628+ 0.0007 and 0.0839+ 0.0004m/s and 0.0421+ 0.0005 and 0.1076+ 0.0004m/s for  AOA, Rore and Omu-Aran for Orisa River. The results of the effects of soil boundary influence showed that the velocity was inversely proportional with the Mannings’ coefficient at all sampling points of both rivers if the geometry of the river channel is kept constant. This  indicates that areas with high velocities are prone to flooding. Further studies should be carried out on more sampling points on the  rivers to confirm flow characteristics of the rivers.