Wave attenuation over a Scirpus mariqueter salt marsh during typhoon Muifa

Salt marshes play a crucial role in mitigating coastal flooding by wave attenuation. However, widespread degradation of these natural barriers due to human activities has exacerbated the hazards associated with large waves during typhoon events. This study presents field observations of wave dynamics and salt marsh characteristics conducted in Chongming Dongtan, located in the Changjiang estuary, in September 2022 under varying weather conditions. The objective was to investigate wave variations over the Scirpus mariqueter salt marsh. The results show that the average wave attenuation during Typhoon Muifa was 6% lower than that under normal wave conditions. Additionally, the maximum significant wave height experienced a 19% reduction in attenuation during Muifa compared to normal wave conditions. Insufficient wave attenuation was attributed to deeper water depths. Furthermore, the drag coefficient was lower during typhoon events, likely due to prolonged inundation durations and larger vertical gaps between the water surface and the top of the Scirpus mariqueter. This study highlights the important role of Scirpus mariqueter in dissipating waves during typhoon events and provides a theoretical basis for wetland conservation and coastal ecological security.