Beach Morphodynamic Response to a Submerged Reef

Abstract

To develop beach engineering, the submerged structure’s primary physical functions have to be understood. This study focuses on submerged structures in order to understand the strategy of reduced wave energy, stabilizing the shoreline and not generating erosion or adversely modifying coastal processes. Important developments have been made since the 1990s, taking into account the functions of recreational amenity. However, non-dimensional models cannot explain the physical mechanisms that generate accretion or erosion morphological features in the lee of the submerged structure. The present study aims to collaborate with the understanding of the mechanism of beach response to a submerged structure. For this, 26 surveys were made using topographic, Lagrangian, and Eulerian hydrodynamic measures during one seasonal cycle of a beach system from Rio de Janeiro (Brazil) with a natural submerged reef or rocky bank V-shape in the plan. This beach system is energetic and intermediate when referring to wave energy conditions and beach states, respectively. The wave breaking vector system on the rocky bank’s geometry was examined in the intermediate and dissipative beach morphodynamic organization. The variability of the wave breaking vector system determines the establishment, deformation, and erosion features in the lee of the structure. During high-energy waves, the submerged structure’s hydrodynamic and morphodynamic processes are transparent. When the submerged structure combines with the dissipative beach state, the surfing wave conditions are improved. These results provide the dimensional and positional references for an engineering proposal for a beach system.