Topographical, Geotechnical and Hydrological Assessment of River Tsatu and Tserefu for Bridge Infrastructural Development, Kwara North, Nigeria

This Environmental assessment aim to facilitate the design and construction of a bridge along the axis that will play a vital role in enhancing the socio-economic activities of the area. South GNSS Galaxy high-precision survey equipment was used for the topographic survey with a reference station equipped with a static GNSS receiver. The data was processed using Global Mapper and Golden Surfer software. Geotechnical field work entailed boring exploratory pits at 2.5-3.0 meters depth intervals using auger tools for sampling and laboratory inference analysis. Hydrological work included measuring the river flow, height and catchment using the flow and dip meters. Findings has shown the area is a northwest-southeast trending ridge line with a centrally located and northerly trending sub-ridge line. Slopes ranged from 0-5% around the lower lying (drainage) areas and ranged between 15% and 40% for the side. Grain size analysis revealed silty-clayey sandy and clayey sandy soil with the sand ranging between 88-96%, followed by clay with 1-13%, silt recorded 0-5% and gravel gave a value of 0-2%. Angle of internal friction varied between 19-31° and shear strength varied between 2-22KN/m2. Free Swelling Index varied between 5.49-14.00. Hydrological properties of the area showed length of Tserefu river to be 7.48km, bed slope of 1.6% and area of watershed of 19,13324607Km2. Tsafu recorded 1.4% bed slope, 2.67km river length and 3,436672092 Km2 watershed. The study concluded that the soil and condition of the area are good for the bridge infrastructural design and construction to facilitate its socio-economic activities.