Numerical Analysis of the Potential Effect of Wetlands on Reducing Tidal Currents in the Liao River Estuary, China

Abstract

In this study, an explicit depth-averaged 2D flow model that considers vegetation effects was established to investigate the interactions between tidal currents and vegetation in coastal wetland waters. Roe’s approximate Riemann solver, coupled with the drying-wetting boundary technique, was proposed to evaluate the interface fluxes and track the moving shoreline. In addition, the vegetation-induced drag force was added to the momentum equations as an internal source. Model validation based on two laboratory experiments demonstrated that the model results were in good agreement with the measured results. The model was then applied to evaluate the interactions between vegetation and tidal currents in the Liao River Estuary, China. The simulation results showed that vegetation played a critical role in attenuating flow velocities in vegetated waters. In the Liao River wetland, the reductions in the amplitudes of the peak depth-averaged velocities in Phragmites austral (P. australis) wetlands were significantly higher than those of the Suaeda heteroptera (S. heteroptera) wetlands. Moreover, the flow velocity changes in the wetland waters also impacted the kinetic energy, creating a new flow field structure. The simulation results also indicated that higher vegetation densities resulted in a larger flow velocity attenuation rate in the vegetated areas.