Phase-resolved Modeling Of Surf Zone Wave Transformation Over Idealized Rough Bottoms

Abstract

Rough rocky seabeds dominate world's coastlines, making accurate modeling of wave transformation in such environments essential for understanding coastal processes and hazards. Wave breaking and friction are critical drivers of wave dissipation over rough seabeds, especially in the surf zone. Phase-resolved wave models, often relying on classical bed shear stress or canopy drag approaches, can fail to capture these processes due to limitations in their physical assumptions, especially for large roughness elements typical of rocky seabeds. The present study adapts the Bulk Canopy Drag (BCD) parameterization, inherited from vegetation and porous media studies, into the 3D non-hydrostatic phase-resolved SYMPHONIE model to simulate wave dissipation over rough seabeds. The model was tested against laboratory experiments (LEGOLAS), using controlled irregular wave forcing propagating over a rough ramp. Results reveal that turbulent drag dominates the outer surf zone, while inertial drag plays a key role in the inner surf zone. A combined optimization of these influences achieved strong agreement with experimental measurements under one irregular wave forcing and a specific bottom configuration. These findings underscore the importance of accurately incorporating both turbulent and inertial contributions into wave dissipation models for the rocky surf zone. The proposed BCD approach provides a promising framework for improving phase-resolved modeling of wave dynamics, with potential applications for more complex field conditions. Future work will aim to extend the approach to diverse roughness configurations and refine empirical coefficients for broader scalability and in situ applicability.