Modeling wave dynamics with coastal vegetation using a smoothed particle hydrodynamics porous flow model

Coastal vegetation serves as an effective nature-based solution for protecting shorelines from erosion and storm surges. A detailed understanding of the dynamic interactions between waves and vegetation is crucial for quantifying the mitigation potential of coastal vegetation during extreme climatic events. This study investigates wave dynamic interactions with coastal vegetation by developing a numerical model using the weakly compressible Smoothed Particle Hydrodynamics (WCSPH) method. The model simulates the effects of vegetation by incorporating vegetation porosity, drag, and inertia forces into the momentum equations. By integrating porosity information at specific background points, the SPH interpolation method effectively treats the interfaces between fluid and vegetation regions, allowing versatility in modeling various vegetation layouts without explicitly simulating their solid structures, which is computationally prohibitive. The numerical model is validated using laboratory-based measurements and analytical models for both submerged and emergent scenarios involving cylindrical and strip-type vegetation. The model is then utilized to investigate the effects of vegetation as both a natural line of defense and a retrofitting solution in front of a sea dike, to quantify the performance of nature-based solutions for enhancing climate resilience in natural and hybrid coastal protection infrastructures. The results reveal that canopy density significantly impacts solitary wave run-up and energy dissipation. For the configurations tested in this study, high-density vegetation reduces normalized wave run-up by 52% compared to simulations without vegetation, while low-density vegetation achieves a 17% reduction. These findings demonstrate the potential of vegetation, particularly at higher densities, to mitigate solitary wave energy and reduce run-up hazards. Furthermore, simulation results indicate that using vegetation as a retrofitting solution effectively mitigates overtopping rates, achieving a 37% reduction with minimal forest density (& empty; = 0.023). These results underscore the effectiveness of nature-based interventions in enhancing coastal protection and resilience.