From deep open seas to intertidal zones, oceanic vegetation is scattered in various regions of the earth, with about 8,000 different vegetation inhabiting worldwide, and about 500 of them in the nearshore waters of Korea.
In the case of Korea, there are macroalgae plants such as undaria pinnatifida, laminaria and hizikia fusiforme along the rocky shorelines of the southern and eastern coasts, and in waters about 30 to 40 meters deep off the islands of Dokdo and Jeju. And in the case of the tideland-rich western coast, salt marsh plants, which make their home in intertidal zones, are dominant in that region. In the oceanic ecosystem, vegetation play important roles as a breeding place and a habitat for fish and shellfish. In addition, if waves propagated from the open seas pass through such vegetation as macroalgaes, wave energy dissipates due to the drag force of the vegetation, leading to wave deformation.
The purpose of this study is to analyze the deformation characteristics of the waves passing through vegetation, considering the vegetation movement caused by the waves. Therefore, this study experimentally investigated the characteristics of the wave deformation caused by the movement of vegetation, by comparing non-moving fixed vegetation like perpendicular structures with moving vegetation which are swayed by wave action. In the hydraulic experiment, a fixed vegetation model made of wooden material and a moving vegetation model made of polypropylene fiber were designed and installed in a 2-dimensional-wave tank which is 15m long, 0.5m wide and 0.6m deep, and then a regular wave has been induced.
The result of the experiment showed that wave reflection occurred in regular intervals regardless of the movement of the vegetation, and the transmission coefficient of the wave had a decreasing trend as wave steepness increased. However, regarding change in the vegetation density, the transmission coefficient decreased as the density increased when the vegetation moved, whereas the transmission rate increased as the density increased when the vegetation didn't move.