AUTHOR=Ma Yuxi , Zhu Longhuan , Peng Zhong , Xue Liming , Zhao Wenzhen , Li Tianyou , Lin Shiwei , Bouma Tjeerd J. , Hofland Bas , Dong Chuning , Li Xiuzhen 

TITLE=Wave attenuation by flattened vegetation (Scirpus mariqueter)

JOURNAL=Frontiers in Marine Science

VOLUME=10

YEAR=2023

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2023.1106070

DOI=10.3389/fmars.2023.1106070

ISSN=2296-7745

ABSTRACT=<p>With the capacity to reduce wave energy and trap sediment, <italic>Scirpus mariqueter</italic> has become an important native species of annual grass for ecology restoration at the Yangtze Estuary in eastern China. Due to seasonal variances of biophysical characteristics, <italic>S. mariqueter</italic> usually bends and breaks in winter, resulting in flattened stems that may reduce its wave attenuation capacity. To investigate the effects of vegetation flattening on wave attenuation, a set of flume experiments were conducted for flattened and standing vegetation under different wave conditions. The model vegetation was designed to represent the wilted <italic>S. mariqueter</italic> collected in winter with dynamic similarity. Results showed that the wave damping coefficient for flattened vegetation (<italic>β<sub>F</sub></italic>) was 33.6%-72.4% of that for standing vegetation (<italic>β<sub>S</sub></italic>) with the same vegetation length. Both <italic>β<sub>F</sub></italic> and <italic>β<sub>S</sub></italic> increased with wave height but decreased with water depth. A wave attenuation indicator (<italic>WAI</italic>) was defined to generate empirical formulas for <italic>β<sub>S</sub></italic> and <italic>β<sub>F</sub></italic> as well as their ratio <italic>β<sub>F</sub>/β<sub>S</sub></italic>. The empirical formulas were then applied to modify the existing standing vegetation-based wave attenuation model for flattened vegetation and performed successfully. Understanding the wave attenuation characteristics of flattened vegetation is essential for the management of ecological restoration and coastal protection.</p>