Response of Suspended Sediment Dynamics Over Eroding and Accreting Tidal Flats to Typhoon Damrey: A Case Study of the Jiangsu Coast

Typhoons are likely to drive intense sediment transport in the coastal zone, changing morphologies of tidal flats, causing siltation of navigational channels and erosion around coastal structures in a relatively short time. Understanding sediment dynamics under typhoons is of great importance for coastal safety. The Jiangsu coast has two typical tidal flats: the accreting type sheltered by the Radial Sand Ridges (RSRs) and the eroding one in the Abandoned Yellow River Delta (AYRD). This makes the Jiangsu tidal flats an ideal case to study the sediment dynamics of different regions with different wave exposures under typhoons. In this study, a coupled storm surge-tide-wave-sediment transport model was established to explore sediment dynamics during Typhoon Damrey on the Jiangsu coast. The results show that the Suspended Sediment Concentrations (SSCs) during Typhoon Damrey were 6.7 kg/m3 and 4.8 kg/m3 in the AYRD and RSRs, respectively, which were 9.7 and 2.8 times larger than that during normal weather. Sensitivity analyses depict that the strong surges and large waves induced by Typhoon Damrey are the two main factors causing changes in SSC. The SSC during typhoon transit (coinciding with spring tides) was averaged and the contribution of different dynamics was extracted separately, and it was found that the average wave contribution to SSC during this period was 68.35% in the AYRD, 77.88% in the transition region and 79.84% in the RSRs. The results of this study can provide guidance for the coastal protection measures during extreme events in different areas with different wave exposures.