Assessing the Influence of the Nature of Slope on Sediment Yield in River Mada Drainage Basin, Akwanga, Nasarawa State, Nigeria

Abstract

This study assessed the influence of the nature of slope on sediment yield in the River Mada drainage basin of Akwanga, Nasarawa State, to determine the rate of surface detachment and delivery downstream. Field measurement using stratified sampling techniques was used to divide the drainage basin into three sub-basins (upper, middle and lower courses), using channel characteristics that are peculiar to any course of a river. Data on slope was collected using field measurements and observations with tools like rope, ranging poles, plumb, and tape. In each sub-basin, six (6) sampled points were measured manually, three (3) on each side of the river, making a total of eighteen (18) sampled points for the slope. A GIS Map of erosion depositional zones of the River Mada drainage basin was produced to show how sediments are eroded. The percentage of slope was measured using the formula, percentage of slope; P = Rise/Run x 100. Where P is the percentage, Rise is the rate of elevation and Run is the distance covered, divided by 100. Regression analysis on the significant effect of slopes/gradient on the sediment yield in the upper, middle and lower courses of River Mada shows that sediment yield in River Mada is dependent on the nature of the slope. The study concludes that the nature of the slope in the Mada drainage basin encourages surface detachment and delivery downstream, which renders surfaces bare and accelerates erosion in the area. The study recommends that there should be tree plantation farming on slopes to reduce surface runoff and the excavation of sediments on slopes downstream. There is a need for the government, through appropriate MDAs, to embark on data gathering on critical environmental variables through in-situ and field measurements using Remote Sensing and GIS, with the view to developing an integrated, comprehensive databank and information systems for environmental monitoring and natural resource management.