Downstream hydraulic geometry across headwater channels in Upper Ogun River Basin, Southwestern Nigeria

Hydraulic geometry is widely applicable in different environments and is quite essential across different channel units. In this study, downstream hydraulic geometry was used to ascertain differences in exponents across headwater channels within a Basement Complex in a humid tropical region. This study was conducted within the Upper Ogun River Basin, Southwestern Nigeria. The basin is approximately 200 km in length and 140 km wide. Eighty-three (83) reaches were sampled across third-order basins within the Upper Ogun River Basin. Hydraulic geometry variables were measured and derived at bankfull using appropriate techniques and basic hydraulic equations, respectively. For the six-individual basins covered, it was found that the exponents (<i>b, f</i> and <i>m</i>) of the downstream hydraulic geometry relations for Q_bf covered a range of: <i>b</i> = −0.12–0.51; <i>f</i> = 0.44–0.67; <i>m</i> = 0.04–0.46. The channels of four basins out of six becomes progressively narrowed and deepened downstream while that of the remaining two becomes progressively wider and shallower downstream.