Narrow Results

The past tsunami events, despite inducing extensive damage to the coastal community, cognized coastal vegetation as a buffer to the inundating tsunami. This, as well as the endangerment of coastal forest as ecosystems, necessitates a deeper understanding of coastal vegetation’s potential for tsunami damage mitigation. The literature highlighted the energy reduction of up to 60% due to the presence of vegetation during tsunami inundation conditions. Thus, several studies in the past and recent times investigated the effect of vegetation on tsunami energy reduction. This chapter extensively reviews in detail the vegetation parameter and flow parameter influence on energy reduction with a review furthering on the hybrid defence system (combination of vegetation and hard structures). The chapter presents a clear idea for building a coastal forest, thereby helping identify the best combination of the parameters for availing the maximum advantage of the vegetation with the available land space.

A three-dimensional σ-coordinate LES model is proposed to simulate hydrodynamic behavior of free surface turbulent flows with vegetation. Vegetation is considered as an internal source of resistant force and a phenomenon model is employed to express the performance of vegetation in the flows. The model is modified from the σ-coordinate LES model developed by Lin and Li (2002, International Journal for Numerical Methods in Fluids, Vol 38, Page 1045-1068). The governing equations of the modified model include additional terms for drag force produced by vegetation and the modified model is distinctive in that not only compound channel flow can be solved but also wave motion through vegetation in coastal region can be taken into account. An operator splitting method, which splits the solution procedure into advection, diffusion and pressure correction steps, is employed so that different numerical schemes can be used for the solution of different physical processes. The model has firstly been applied to simulate the hydrodynamic behavior of turbulent flow in compound open channel with partly vegetated region. Then by using the model the attenuation of wave movement due to vegetation in coastal region is simulated. The results reveal that the present model has the capacity of describing three-dimensional structure of large eddy appearing in free surface turbulent flows with vegetation. It is believed that the model will become a useful tool to pursue further study of wave hydrodynamics in coastal region with the presence of aquatic vegetation.