Experimental Study On Hydrodynamics Of The Root And Stem Under Regular Wave Conditions

Shorelines have been increasingly eroded by water waves because of changes in climate and environment resulting in sea level rise and storm surge.Coastal erosion and storm surge pose a huge threat to people's lives and property and buildings in coastal regions.Previous studies show that aquatic vegetation has capacity of reducing wave energy,which thus has started to attract the attention of coastal engineers.To mitigate the disaster of storm surge and coastal erosion,it is important to investigate hydrodynamics of vegetation.Wave attenuation by aquatic vegetation is down to interactions of each component of vegetation and water waves.Coastal aquatic vegetation commonly consists of roots,stems and canopies,while for typical aquatic trees like mangroves their roots and stems dominate wave dissipation.Therefore,the present study mainly focuses on hydrodynamics of the root and stem of such vegetation,aiming to provide theoretical guidance for mitigating hazards.Concerning mangroves prototype in real systems,experiments were conducted to study hydrodynamics of the root and stem with a combination of two water depths,four wave heights,four wave periods and three vegetation models.The effects of hydrodynamic factors and vegetation factors on wave decay along vegetation field,transmitted coefficients and vertical and lateral velocity structure were discussed.Results show that wave height increase was observed within the vegetation region and for different vegetation models the vertical velocity profiles can be divided into three parts.