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.