6. The contribution of bank and surface sediments to fluvial sediment transport of the Pra River
Abstract
Sediment source studies involving a simple mixing model was undertaken in the Pra River Basin in Ghana using a single tracer 210Pb to determine the relative contribution of surface and bank sediments to the fluvial sediment transport. Sediment source tracing was performed on the basis of sub-basins by comparing the concentration of 210Pb in fluvial sediments to the bank sediments and potential surface sediment sources. The potential sediment source types sampled for analysis included surface sediments from arable top soils, illegal mining sites, path/untarred roads leading to rivers, gullies and gutters from settlements and farms. For bank erosion, river channel bank materials were sampled. Lead-210 fallout was determined by alpha spectrometry using the low background Gas-less Automatic Alpha counting system (Canberra iMatic™). Results showed that bank material was the dominant sediments and accounted for over 60% of suspended sediment loads in all tributaries. Measures should be put in place to control the entrainment of bank materials since bank sediments constitute a larger proportion of the fluvial sediments. High fluvial sediment load is known to have geomorphological, hydrological, water resource management and ecological implications.
