Performance Assessment of a Hybrid Green-Grey Submerged Breakwater (HGG-SB) with Submerged Aquatic Vegetation

In this study, a two-dimensional hydraulic model experiment was conducted to evaluate the hydrodynamic performance of the proposed hybrid green-grey submerged breakwater (HGG-SB) under regular wave conditions, comparing it with a single-row submerged breakwater (SB) and a double-row submerged breakwater (DSB). Although submerged breakwaters are widely deployed for coastal protection, economic and functional challenges remain. To reduce these issues, this study conceptualizes the HGG-SB—a double-row configuration integrated with artificial vegetation—focusing primarily on evaluating its fundamental hydrodynamic performance. For a systematic assessment, two-dimensional hydraulic experiments were conducted under a comprehensive matrix comprising 7 cross-sectional configurations and 22 incident wave conditions. The results revealed that this composite system achieved a wave dissipation efficacy comparable to a SB, whereas the efficiency of the DSB setup was confirmed at approximately 90%. These experimental results indicate that, despite the physical scaling limitations of the artificial vegetation, expanding the inter-structure spacing and vegetation zone enhances wave deformation control and dissipation. Consequently, even within the constraints of a two-dimensional physical experiment, the HGG-SB achieves hydrodynamic performance comparable to a SB while reducing the cross-sectional area of its structural material by 25%.