Sediment Continuity for Rivers with Non-Uniform Sediment, Dunes, and Bed Load Transport

Abstract

Models describing the interaction among grain size-selective sediment transport, the vertical sorting profile within the bed, and bed level changes constitute a critical component of morphological model systems for rivers with non-uniform sediment. This interaction is described in terms of sediment continuity models. Hirano (1971) was the first to develop such a sediment continuity model. In the Hirano active layer model, the bed is divided into a homogeneous top layer, i.e. the active layer, and an inactive substrate. Only sediment in the active layer interacts with the flow and participates in the transport process. Sediment fluxes between the active layer and the substrate occur only when there is a change in the average bed level. In the last few decades, a number of variants to the Hirano active layer model have been proposed in order to overcome several shortcomings and obtain a better description of vertical sediment sorting mechanisms within the bed.