Dual Behavior of Suspended Sediment Concentration in a Regulated River

Better understanding of suspended sediment transport processes allows for better management of both rivers and coasts. Based on field data and sediment transport energy theory, this study presents an analysis on the suspended sediment hysteresis in the Lower Tenryu River of Japan in connection to the channel carrying capacity of suspended sediment and morphological characteristics. The transport of suspended sediment in the river exhibited dual behaviors according to the magnitude of flood. It was transport-limited in a 10-year flood while supply-limited in a 30-year flood. In the supply-limited case, the temporal variation of suspended sediment concentrations followed the hydrograph well. In the transport-limited case, however, there was a time lag between peak discharge and maximum suspended sediment concentration. The mechanism of time lag was further clarified to be different for the 10-year flood and a small flood. The objective of this paper is to shed some new light on the relationship of suspended sediment to flow and channel conditions.