Adjusting the Critical Shields Parameter Within Salt Marshes Based on Vegetation-Induced Resuspension

Salt marshes are vegetated coastal habitats with current-and wave-driven transport of fine sediment particles. Vegetation-induced turbulence reduces the critical velocity for sediment resuspension within salt marsh canopies, which is not captured by transport models developed for bare beds. Therefore, a compre-hensive flume experiment was conducted to quantify the reduction of the critical velocity for resuspension in wave-current flows and to provide recommendations for sediment transport models. The experiments with artificial Spartina Anglica vegetation and two non-cohesive grain sizes under combined wave-current flows showed that vegetation reduced the critical velocity by 35–64% compared to a bare bed depending on a ratio of the current and wave velocity. These results were not sensitive to variations in stem density and grain size. We showed that the reduc-tion in critical velocity was equivalent to a reduction of 57–88% of the critical Shields parameter depending on the same ratio of the current and wave velocity. We recommended that the so-called vegetation-adjusted critical Shields parameter could be implemented in sediment transport models to include vegetation-induced resuspension.