Modeling coastal wave attenuation with hybrid vegetation–breakwater structures

Wave attenuation is essential to mitigate coastal erosion and safeguarding nearby infrastructure. This study presents analytical and computational approaches to model wave evolution over a hybrid coastal protection measure combining vegetation and low-crested breakwaters, based on the Shallow Water Equations (SWEs). In estimating wave transmission coefficient resulting from the interaction between waves, vegetation, and breakwaters, an analytical solution is obtained by applying the separation of variables technique, whereas a staggered finite-volume scheme is developed to conduct numerical simulations. Comparisons of the analytical solutions, numerical simulations, and experimental data demonstrate strong agreement, with relative errors below 0.13% with respect to analytical solutions and below 3.4% compared to experimental measurements, indicating a high degree of accuracy of the proposed model. The results imply that the hybrid system achieves greater wave amplitude reduction than vegetation-only or breakwater-only configurations. Sensitivity analyses reveal that the size and friction factor of both breakwaters and vegetation have comparable effects on wave attenuation, with higher values leading to greater reduction. Notably, adjustments to the friction factor have the most significant impact on wave attenuation compared to the other parameters examined. These findings contribute to enhancing the design of hybrid coastal defense systems and provide valuable insights for sustainable coastal engineering and climate resilience planning.