Wave Overtopping of Rubble Mound Structures: The Combined Effects of Water Depth and Still Water Level

The overtopping phenomenon is the main cause of coastal flooding and the susceptibility of coastal defense structures. Recent investigations have demonstrated that local hydrodynamics are considerably altered by progressive erosion and fluctuations in the water level in front of structures, with the direct impact of higher and more energetic waves on the structure increasing the overtopping volume. These studies show that the quantity of water that is overtopped is influenced by a variety of factors, including wave height, wave period, and sea water level. However, the fluctuation in the bottom elevation in front of coastal structures (due to coastal erosion, for instance) is one of the potential causes of the growth of this phenomenon over time. This work evaluates the impact of water depth variations in front of sea structures on overtopping. This paper introduces a numerical methodology that uses a computational fluid dynamics (CFD) method to verify the experimental results obtained in a two-dimensional hydraulic channel, on beach profiles in front of structures armored with Antifer-type blocks. Unlike traditional homogeneous porous media models, the individual blocks (Antifer) were discretized geometrically in 3D by superimposing them in the numerical domain. Additionally, the morpho dynamic evolution of the sandy beach in front of the structure was simulated. The purpose of this paper is to evaluate the efficacy of an advanced CFD methodology as a prediction and design tool for coastal defense systems. By comparing numerical results with physical models and mathematical formulas, this study assesses the accuracy of numerical approaches in reproducing beach evolution and the internal flow of coastal defense structures. While the CFD model demonstrates strong predictive capabilities under standard scenarios, notable discrepancies are observed under specific experimental conditions. These limitations and their implications for design practice are compared and discussed.