A hybrid model framework for wave attenuation by flexible vegetation in current-wave flows
Weifeng Ye (Sun Yat-sen University)
Zhan Hu (Sun Yat-sen University, Ministry of Education Hangzhou)
Khanh Linh Phan (Thuy Loi University)
Marcel Stive (TU Delft - Civil Engineering & Geosciences)
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Abstract
Salt marsh wetlands can serve as an efficient buffer against storm waves. However, accurate quantification of the wave attenuation process is challenging. Previous modeling approaches generally ignored the posture of flexible vegetation and the impact of wave-induced vertical velocity, which may lead to underestimated wave attenuation. To address this issue, we developed a new hybrid model framework for wave attenuation by flexible vegetation. This framework incorporates a machine learning predictor for vegetation posture via a bending coefficient and a modified semi-analytical model that accounts for wave attenuation by bent rigid vegetation. This model framework is compared with our own experimental data and additional data from literature. The model shows that flexible vegetation can induce up to 21 % greater wave attenuation than rigid vegetation in near-emergent testing conditions due to the contribution of wave-induced vertical velocity. Our model framework can accurately reproduce such a contribution (up to 60 % of the total wave energy), and avoid underestimation of attenuation (R2 = 0.96). This study develops a novel tool integrating mechanical analysis and data-driven approaches to quantify wave attenuation by flexible vegetation, enabling the assessment of coastal protection by salt marshes and seagrass wetlands.