Phase-resolved modelling of wave transformation in the surf zone over idealised rough bottoms

Abstract

In order to understand and predict coastal flooding processes in rocky environments, it is necessary to take into account bottom roughness, which plays a key role in wave transformation processes and in general coastal dynamics. The present work aims to implement a parameterisation of roughness-induced dissipation in 3D non-hydrostatic phase-resolved wave models, based on the Symphonie code (MARSALEIX et al., 2019). The modified model is compared with laboratory experiments carried out on a surf zone with a linear slope (DEALBERA et al., 2024). Different irregular waves were tested on various configurations of bottom roughness (represented by block configurations of different sizes and distributions). Wave generation and dissipation induced by breaking were first parametrised with respect to laboratory data on smooth bottoms. The different roughness cases were then studied on the basis of two distinct strategies for parameterising bottom friction, namely the bottom stress approach and the canopy drag approach. The performance of these two approaches is assessed by comparing the model results with measurements of the cross-shore significant wave height profile for different bottom configurations. On the basis of this work, recommendations on the choice of dissipation parameterisations will be made.