Experimental Study on Wave Attenuation by Vegetation Under Variable Water Levels

Abstract

This study investigates the wave energy dissipation capacity of saltmarsh vegetation under varying water depth and density conditions, focusing on its wave attenuation mechanisms. Although existing studies have demonstrated the significant role of vegetation in wave energy dissipation, traditional models often overlook the complexity of stem-leaf structures, resulting in inaccurate descriptions of wave-vegetation interactions. In particular, the applicability and accuracy of these models in evaluating the actual contribution of vegetation to wave energy dissipation remain to be improved. Based on the wave flume experiments investigating the wave energy dissipation effect of Suaeda salsa, this study conducts a comparative analysis between vegetation models and cylindrical rods. Experimental scenarios were designed to cover a range of water depths (0.1 m - 0.3 m) and wave heights (0.05 m and 0.10 m). A stem-leaf correction factor (φ) was introduced to improve traditional drag coefficient calculations, addressing limitations in existing models regarding complex vegetation structures. Results reveal that the Suaeda salsa model, due to its complex stem-leaf structure, exhibits stronger wave energy dissipation capacity. Compared to the rigid cylindrical rod model, the wave height attenuation coefficient of the vegetation model is approximately 22.67% lower, and therefore its energy dissipation effect is significantly enhanced. Furthermore, the stem-leaf correction factor shows a nonlinear relationship with water depth, with rapid changes at shallow depths and stabilization at greater depths. Incorporating the correction factor improves the drag coefficient (Cd) and Keulegan–Carpenter number (KC) fitting performance (R2=0.53), significantly enhancing the accuracy of wave energy dissipation calculations. The corrected damping coefficient (βcv) also achieves higher consistency with experimental measurements (𝛽m). By proposing an improved vegetation-based wave attenuation model, this study advances the understanding of the role of vegetation structure in wave energy dissipation, providing theoretical support and experimental evidence for the design of eco-friendly coastal protection technologies.

Keywords: Suaeda salsa model, wave attenuation, stem-leaf correction factor, drag coefficient, damping factor