3-DIMENSIONAL SIMULATION OF SUSPENDED SEDIMENT TRANSPORT OFF THE DIAOKOU RIVER MOUTH, THE YELLOW RIVER

A 3-dimensional numerical model was used to investigate the suspended sediment transport off the Diaokou River Mouth of the Yellow River due to the absence of in-situ observations on estuarine sediment dynamics in this area prior to 1976. Two patterns of sediment dispersion were identified as the hypopycnal plume in the surface layer and the hyperpycnal flow in the bottom layer, both showing significant intra-tidal variability due to the interactions between river flow and tidal current. The surface river plume (hypopycnal) was deflexed laterally by the coast-parallel tidal current, which induces significant along-shore sediment transport but limited cross-shore sediment transport. River delivery of high-concentrated sediment in the flood season produces plunging hyperpyucnal flows at the Diaokou River Mouth that acts as a conduit for the northward sediment delivered to the deltaic front. The hyperpycnal flow results in higher sediment flux in the bottom layer than the contribution of surface hypopycnal plume by one order in magnitude. Meanwhile, the hyperpycnal-induced flux exponentially decreases along the subaqueous slope off the river mouth. Approximately 75% of the river-delivered sediment was deposited in the nearshore area shallower than 10 m, whereas the rest 25% of sediment was transported to the deltaic front. These highlighted the dominant role of the estuarine hyperpycnal process in cross-shore sediment transport. The numerical results agree with the previous conclusion on the accumulation-erosion pattern off the Diaokou River Mouth based on the bathymetric changes, and are also consistent with the analysis of sediment records in this area.