Unsteady flow in straight alluvial streams. Part 2. Transition from dunes to plane bed

Abstract

The effect of suspended sediment on the modification of individual dunes in unsteady channel flow is analyzed. The model is an extension of that developed by Fredsøe (1979), in which the change of the dune dimensions was analyzed assuming that the transport of sediment mainly occurs as bed load. By including suspended sediment, it is possible to describe dune behaviour at high sediment transport rates, for which the dunes are washed out, so the bed at sufficiently high bed shear stress becomes plane. The model is compared with laboratory experiments and the agreement is reasonable. The effect of temperature variations on dune dimensions is incorporated in the analysis.