Wave Height Attenuation over a Nature-Based Breakwater of Floating Emergent Vegetation

Abstract

The nature-based breakwater of floating emergent vegetation (BFEV) provides protection for water banks and various engineering structures from wave erosion. Compared with the convenient hard breakwater, the BFEV is beneficial to the resilient and sustainable development of rivers, lakes, coasts, and marine areas because it is free of new pollution. As a new breakwater, the unrevealed effect and efficiency of the BFEV on wave attenuation are to be investigated through a set of 312 physical tests in a rectangular indoor water flume in the present study. Results show that the wave height attenuates by 38–62%. Based on statistical methods, the main influencing factors of the wave transmitted coefficient (Ct) are found to be closely dependent on three conventional and newly proposed dimensionless parameters (λ1, λ2, λ3, λ4). Three conventional parameters include the wave orbital velocity, wave period, and the BFEV-width and stem spacing-based parameter (λ1, λ2), and the ratio of stem spacing to wave height (λ3). The newly proposed parameter (λ4) is the ratio of gravity to wave orbital acceleration, which is significantly positively related to the wave height attenuation. A multiple linear regression formula for Ct based on these four parameters is obtained with a high correlation coefficient of 0.958. This study is expected to supplement the wave attenuation data of this new breakwater and provide fundamental theory for the design and construction of the BFEV.