Q. Chen
Yan Ding
Navid H. Jafari
Hongqing Wang
Bradley D. Johnson
Ling Zhu
2023
<div id="abstracts" class="Abstracts u-font-serif"><div id="d1e1297" class="abstract author"><div id="d1e1300"><p id="d1e1301"><span>Coastal regions are susceptible to increasing flood risks amid climate change. Coastal wetlands play an important role in mitigating coastal hazards. Vegetation exerts a drag force to the flow and dampens storm surges and wind waves. The prediction of wave attenuation by vegetation typically relies on a pre-determined drag coefficient </span><span class="math"><span id="MathJax-Element-7-Frame" class="MathJax_SVG" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><msub is="true"><mrow is="true"><mi is="true">C</mi></mrow><mrow is="true"><mi is="true">D</mi></mrow></msub></math>"><span class="MJX_Assistive_MathML">C<sub>D</sub></span></span></span><span>. Existing </span><span class="math"><span id="MathJax-Element-8-Frame" class="MathJax_SVG" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><msub is="true"><mrow is="true"><mi is="true">C</mi></mrow><mrow is="true"><mi is="true">D</mi></mrow></msub></math>"><span class="MJX_Assistive_MathML">C<sub>D</sub></span></span></span><span> formulas are subject to vegetation biomechanical properties, especially the flexibility. Accounting for vegetation flexibility through the effective plant height (EPH), we propose and validate a species-independent relationship between </span><span class="math"><span id="MathJax-Element-9-Frame" class="MathJax_SVG" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><msub is="true"><mrow is="true"><mi is="true">C</mi></mrow><mrow is="true"><mi is="true">D</mi></mrow></msub></math>"><span class="MJX_Assistive_MathML">C<sub>D</sub></span></span></span><span> and the Reynolds number </span><i><span class="math"><span id="MathJax-Element-10-Frame" class="MathJax_SVG" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mrow is="true"><mi is="true">R</mi><mi is="true">e</mi></mrow></math>"><span class="MJX_Assistive_MathML">Re</span></span></span></i><span> based on three independent datasets that cover a wide range of hydrodynamic conditions and vegetation traits. The proposed </span><span class="math"><span id="MathJax-Element-11-Frame" class="MathJax_SVG" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mrow is="true"><msub is="true"><mrow is="true"><mi is="true">C</mi></mrow><mrow is="true"><mi is="true">D</mi></mrow></msub><mo linebreak="goodbreak" linebreakstyle="after" is="true">&#x2212;</mo><mi is="true">R</mi><mi is="true">e</mi></mrow></math>"><span class="MJX_Assistive_MathML">C<sub>D</sub>−<i>Re</i></span></span></span><span> relationship, used together with EPH, allows for predicting wave attenuation in salt marshes with high accuracy. Furthermore, a total of 308,000 numerical experiments with diverse wave conditions are conducted using the proposed </span><span class="math"><span id="MathJax-Element-12-Frame" class="MathJax_SVG" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mrow is="true"><msub is="true"><mrow is="true"><mi is="true">C</mi></mrow><mrow is="true"><mi is="true">D</mi></mrow></msub><mo linebreak="goodbreak" linebreakstyle="after" is="true">&#x2212;</mo><mi is="true">R</mi><mi is="true">e</mi></mrow></math>"><span class="MJX_Assistive_MathML">C<sub>D</sub>−<i>Re</i></span></span></span><span> relationship and EPH to quantify the wave attenuation capacity of two typical salt mash species: </span><i>Elymus athericus</i><span> (highly flexible) and </span><i>Spartina alterniflora</i><span> (relatively rigid). It is found that wave attenuation is controlled by wave height to water depth ratio and EPH to water depth ratio. When swaying in large waves in shallow to intermediate water depth, a 50-m-long </span><i>Elymus athericus</i><span> field may lose up to 30% capacity for wave attenuation. As wave height increases, highly flexible vegetation causes reduced wave attenuation, whereas relatively rigid vegetation induces increased wave attenuation. The leaf contribution to wave attenuation is highly dependent on the leaf rigidity. It is recommended that leaf properties, especially its Young’s modulus be collected in future field experiments.</span></p></div></div></div>
application/pdf
10.1016/j.coastaleng.2022.104256
en
Elsevier
Towards a unified drag coefficient formula for quantifying wave energy reduction by salt marshes
article