Huanghua Harbor, located in the south-west coast of Bohai Bay, China, has frequently encountered severe channel siltation with sorting sedimentation along the channel during storm events since its construction. For prediction of channel siltation, a 3D numerical model of multi-fraction sediment transport based on the coupling of modified EFDC model and SWAN model is developed to investigate the sediment transport. It is shown from simulated results that the sorted sedimentation in the channel was well simulated in storm events, and the high sediment concentration near sea bed for silty coast during storm process can also be basically reflected by the model. Keywords: EFDC model; SWAN model; Sorting Sedimentation; multi-fraction sediment; sediment concentration INTRODUCTIONHuanghua harbor is a coal-export harbor, located at Bohai Bay, China. It is sited on a typical silty coast with very mild slope, and the medium diameter (d 50 ) on the surface layer of the beach bed is 0.0044-0.0689mm. Huanghua harbor has frequently encountered severe channel siltation during storm events since it was constructed. Extensive researches have been carried out to explore the mechanism of sediment transport and channel siltation of Huanghua Harbor. Zhang et al. (2006) and Zhao (2006) developed 2D and 3D numerical models respectively to investigate the sediment transport and channel siltation of Huanghua Harbor in storm events. Yan (2008) developed the vertical concentration profile expressions with high concentration near sea bed for silt suspension due to waves or combined waves and current.However, the properties of sorting sedimentation along the channel were not fully described in the previous models. Therefore, the objective of the present paper is to develop a numerical model to simulate the sorting sedimentation along the channel. For typical silty coasts interested here, the sediment is mainly suspended by wind waves and transported by current, so the combined wavecurrent action is very important. In shallow water, the wave breaking also plays important roles in the vertical concentration distribution of suspended sediment. In addition, the high concentration layer near the sea bed plays a significant role in the severe channel siltation. Therefore, for prediction of channel siltation of Huanghua Harbor on silty coast, a sediment transport model incorporating the above effects is needed. A 3D numerical model for multi-fraction sediment transport based on the coupling of modified EFDC model and SWAN model is developed and applied in the present paper to investigate nearshore sorting sedimentation and the channel siltation process of Huanghua Harbor under the combined action of wind, waves and current.

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