Land use and sediment delivery ratio in the Opa Basin, south-western Nigeria. (133)
Keywords:Land use, Suspended sediment yield, Non-channel sediment yield, Sediment Delivery Ratio
AbstractThis study aimed to determine the relationship between basin physiographic land-use attributes and sediment delivery ratios (SDRs) in 19 (1st order), 5 (2nd order), 1 (3rd order), and 1 (4th order) basins in a cascading system within the Opa Reservoir Catchment. The studied basins were monitored for one year especially for determination of sediment loss on slopes and from channels with emphasis on ascertaining the SDR. The results of this study showed that SDR in the built-up area basins (with mean value of 76.79%) was higher than those obtained from basins cultivated to field crops, to cacao, and forested basins with mean values of 60.64, 54.54, and 47.99%, respectively. Basin SDR correlated significantly with most of the land-use or vegetation attributes except X6, ( per cent basin area under perennial crops) with which it had a negative correlation (r = -0.380) and X7 (per cent basin area under cultivated field crops). Also, SDR correlated poorly with most of the basin morphometric attributes except basin area with which a negative correlation (r = -0.438) was sustained. Between the basin physiographic and land-use or vegetation attributes considered in this study, only per cent basin area built up (X9) was included in an equation derived for the studied basins. In fact, this variable explained about 73% (R2 = 0.729) of the variations in the SDRs in the studied basins. This implied that land use, specifically per cent basin area built-up, is the most important predictor of SDR in the study area.