Title: “Numerical Investigation of Tsunami and Storm Wave Attenuation by Vegetation Using a 3D RANS Model
Traditionally shoreline protection has involved construction of hard structures such as breakwaters and jetties to dissipate and reflect the wave energy but these structures may alter the near shore hydrodynamics and morphodynamics. On the other hand, vegetation has been recognized as a natural protective measure to dampen tsunami and storm waves. Understanding of wave-vegetation interaction is essential for assessing the ability of vegetation patches, such as wetlands, to mitigate coastal flooding and tsunami dangers. In this study the wave attenuation by vegetation is investigated numerically using a 3-D model which solves the Reynolds-Averaged Navier-Stokes equations (RANS) by means of a finite-volume method based on collocated hexahedron mesh. A mixing length model is used for turbulence closure of the RANS equations. The water surface boundary is tracked using the Volume-of-Fluid (VOF) method with the Compressive Interface Capturing Scheme for Arbitrary Meshes (CICSAM) to solve the VOF advection equation. The presence of vegetation is taken into account by adding the vegetation drag and inertia forces to the momentum equations. The model is validated by several laboratory experiments of tsunami and short wave propagation through vegetation over flat and sloping beds. The comparisons show good agreement between the measured data and calculated results, but the swaying motion of flexible vegetation which is neglected in this study can influence the accuracy of the wave height predictions.