Numerical and experimental investigations on wave transmission reduction using vegetation models

Numerical and experimental investigations were conducted using vegetation models with varying leaf thicknesses, meadow lengths, and friction coefficients, to evaluate the efficacy of vegetation in reducing wave transmission under different wave heights, periods, and submergence conditions. A modified shallow-water model considering the effect of friction coefficient as a function of several wave characteristics was developed. The model was solved numerically using a staggered finite volume model. The numerical model was validated using experimental data. Good agreement was observed between the experimental and numerical results, particularly in terms of the wave amplitude and phase. A genetic algorithm was used to derive empirical formulas using the friction coefficient as a function of different vegetation and wave parameters. The results showed that increasing the leaf thickness increased the friction coefficient and reduced the wave transmission. However, increasing the meadow length had a greater effect than increasing the leaf thickness. An emergent meadow covered the entire water column. Hence, it yielded the highest friction coefficient and wave transmission reduction among all tested submergence conditions. A sensitivity analysis was performed to assess the effects of the wave height, wave period, and leaf thickness. The results indicated that the maximum reduction in wave transmission was achieved under emergent conditions with high wave energies, short wavelengths, and thick leaves. This was attributed to enhanced wave–vegetation interaction, wave breaking, and energy dissipation. The observations of this study will aid coastal engineers in selecting the optimal leaf height, leaf thickness, and meadow length to achieve the desired reduction in wave transmission.