Wave Attenuation bySpartina alternifloraunder Macro-Tidal and Storm Surge Conditions

Salt marshes are coastal wetlands that provide many ecosystem services. They protect coasts from erosion, storm surge, and small tsunami by dissipating wave energy. Plant flexibility has been reported to reduce drag force on and wave attenuation of marsh plants. In this study, we proposed a new drag coefficient formula to account plant flexibility so that the classical theory based on rigid cylinders can be extended to predict wave decay by flexible plants. To validate this new formula, the field survey was conducted in the North Hangzhou Bay, China. The wave attenuation was measured in aSpartina alternifloramarsh under a combined macro-tidal and storm surge condition, during which strong bending motions of the plants were observed. The new formula provided better predictions of wave decay than that by the traditional drag formula when compared to the field data measured in both the present study and the earlier studies.