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

Abstract 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 comprehensive 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 reduction 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.