Numerical Analysis of the Potential Effect of Wetlands on Reducing Tidal Currents in the Liao River Estuary, China
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Numerical Analysis of the Potential Effect of Wetlands on Reducing Tidal Currents in the Liao River Estuary, China Mingliang Zhang 1 & Hui Xu 1 Received: 19 November 2019 / Accepted: 24 August 2020 # Springer Nature Switzerland AG 2020
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. Keywords Liao River wetland . Finite volume method . Drying-wetting boundary . Wetland plants . Vegetation-current interactions
1 Introduction Estuarine wetland ecosystems are typically formed in the intertidal flats of coastal domains and thus are a common zone of interaction between terrestrial areas and coastal waters. Numerous salt marsh plants (e.g., Suaeda heteroptera, Spartina alterniflora, and pickleweed) occurring in estuarine wetlands provide a range of ecosystem service functions for the underlying chemical, physical, and biological processes [1]. These plants can transfer biomass and energy across the water [2], purify polluted water by absorbing heavy metals and nutrients [3], and provide an overwater and low-flow habitat for organisms [4]. Wetland plants also act as a non-intrusive buffer to protect coastal communities from the erosion of waves, tidal currents, and extreme weather events by reducing hydrodynamic energy [5]. Wetland vegetation is thus regarded as an effective option for risk * Mingliang Zhang [email protected] 1
School of Ocean Science and Environment, Dalian Ocean University, Dalian 116023, Liaoning, China
reduction and adaptation, providing an important service to the ecosystem [6–8]. Over the last decade, several numerical models have been successfully applied to reproduce hydrodynamic processes and simulate the flow characteristics of large tidal estuaries [9]. The characterization of hydr
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