Effects of overbank flow on fluvial sediment transport rates

Abstract

Some small-scale laboratory results are presented concerning sediment transport rates and stage–discharge relationships in compound channels. The sediment transport data confirm the hypothesis of Ackers (Proceedings of the Institution of Civil Engineers, Water, Maritime & Energy, 1992, 96, No. 6, 167–178) that the bed load concentration generally increases up to bankfull flow, then peaks at around this discharge, before declining again with increasing overbank discharge. Experimental data concerning velocity and boundary shear stress distributions, the interaction between the floodplain and the main channel, and alluvial resistance are also presented. Simple empirical relationships summarise the discharge, sediment transport rate, division of flow, resistance, and boundary shear force data, to aid comparison with other experimental studies and numerical river simulation models that simulate the geomorphological response of rivers to flood events.