Assessment of geomorphic and morphometry characteristics of parts of Shasha and Opa river basins in Obafemi Awolowo University Campus, Southwestern Nigeria

Abstract

Geomorphic and morphometry characteristics of parts of Shasha and Opa Basins in Obafemi Awolowo University campus, Ile-Ife, southwestern Nigeria were assessed through the analysis of basin linear, areal and shape parameters with a view to quantitatively describe the hydrological characteristics of the area. The campus is drained by Rivers Shasha and Opa and their tributaries. Stream order, stream number, stream length, mean stream length, stream length ratio, length of over land flow, confluence factor, form factor, elongation ratio, stream segment density, drainage density, drainage texture and slope within the campus were determined through the evaluation of topographic, drainage, and land use and land cover maps. The campus is drained mostly by River Opa (4^th order channel) and its tributaries while the remaining part (i.e. northeastern and northwestern parts of the campus) is drained by River Shasha (3^rd order channel) and its tributaries. The mean 1^st, 2^nd and 3^rd stream orders of River Shasha were 0.42, 0.54 and 1.03 km, respectively; while the mean stream length for the 1^st , 2^nd , 3^rd and 4^th stream orders of River Opa were 0.40, 0.64, 1.84 and 4.07 km, respectively. The average length of overland flow within the Shasha sub-basin was 0.25 km, while the average - length of overland flow within the Opa sub-basin was 0.15 km. Stream segment density increased from 0.16 km to 3.18 km in River Shasha and 0.08 km to 4.33 km in River Opa. Increased stream segment density from lower to higher stream order could have been influenced by increased fracture control of streams from lower to higher stream order. The predominant trend of the streams were NE-SW and NW-SE, suggesting the influence of differing lithologies or tectonic activities, where streams must have developed by taking advantage of the local relief for the varying stream flow directions.