A Physically Based Model of Deposition, Re‐Entrainment, and Transport of Fine Sediment in Gravel‐Bed Rivers

Abstract

AbstractInterpreting the links between transient in‐channel fine sediment storage and the dynamics of suspended sediment transport during flood events helps the understanding of river geomorphology, and also the impacts of fine sediment on water quality and bed habitats of rivers and downstream receiving environments. We present a unique physically based model of suspended sediment transport which is intimately coupled with fine sediment deposition and re‐entrainment processes within the gravel bed. This multi‐size fraction theory provides unique information about the effect of fine sediment size classes due to their dynamics and associated river bed changes in net deposition. The data from a series of flood events from the Oreti River, located in Southland, New Zealand were used to test the ability of this theory to provide a description of the dynamics of the fine sediment size distribution, their concentration, load, and rate of river bed deposition and re‐entrainment. After calibration of the model using the data from one flood event, the model provides good agreement between observed and modeled fine sediment concentration and event load for seven subsequent test events. One of the main applications of this theory in future is for routing suspended sediment concentration and changes on fine sediment deposition down a river network.