Effects of intertidal wetland vegetation and suspended sediment on flow velocity profiles and turbulence characteristics

•Velocity of flow over flexible vegetation collected from field with three submerged conditions is investigated.•The turbulence intensity and Reynolds stress reach the peak value below the top of the deflected vegetation height.•The standard mixing length hypothesis combined with Reynolds stress distribution is used to derive a new velocity profile.•Through the fast Fourier transform, coarse sediment can influence the flow turbulence more easily than fine sediment.

Intertidal wetland vegetation has an important role in flow structure, suspended sediment movement and geomorphology evolution. This study performed a flume experiment using Scirpus mariqueter from the field to investigate the impact of wetland vegetation on flow structure. The experimental plans were designed based on the relative depth of flow depth to vegetation height, i.e., non-submerged, moderately submerged and completely submerged conditions. Based on the measured Reynolds stress distribution, the classical mixing length hypothesis was used to derive the new velocity profiles inside the canopy. The good agreement of the results demonstrated that this method can be used to predict the velocity distribution of the submerged flow with flexible vegetation. Through statistical analysis combined with the theory of the boundary layer and sediment movement dynamics, the turbulence intensity and fine sediment distributions within the canopy were also obtained. The results reveal the mechanism of the effect of vegetation on the water and sediment of tidal flat in theoretical terms and enhance the understanding of hydrodynamics within the canopy.

Graphical abstractThe Reynolds stress distributions of the submerged condition in (a) profile #4; and the new derived velocity profile (b) profile #4 in run MU_M_SM.Download high-res image (93KB)Download full-size image