In the ocean, there are about 8,000 different vegetation worldwide, and about 500 of them are inhabiting in the nearshore waters of Korea. Generally, oceanic vegetation are largely categorized into macroalgae and marine angiosperms, and macroalgae consists of blue-green algae, green algae, brown algae, red algae, etc. In particular, about 70% of the macroalgae inhabiting in the nearshore waters of Korea belong to the red algae category. Belonging to the marine angiosperms are sea grasses, salt marsh plants and mangroves which are semi-land vegetation and the like. There are 57 species of ascidians worldwide, and in Korea, zestera, which is mostly inhabiting in the areas of Handong of Gyeongnam Province and Wando of Jeonnam Province, belongs to this group. Among semi-land vegetation, mangroves mainly inhabit in tropical regions whereas a variety of salt-marsh plants thrive even in the west sea of the Korean peninsular.
Oceanic vegetation such as macroalgae and oceanic phanerogamic plants play important roles in the oceanic ecosystem, providing living spaces to fish and shellfish and purifying pollutants infiltrating from the land into the seas. In addition, if waves propagated from the open seas pass through these vegetation regions, the heights of the waves are decayed as wave energy is dispersed due to the drag force of the vegetation.
In this study, a hydraulic model test was conducted using a 2-dimensional wave tank which is 15m long, 0.5m wide and 0.6m deep, in order to experimentally analyze the effects vegetation density has on the dispersion of wave energy, as one of the causes of the drag force of the vegetation.
The result of the hydraulic model test showed that as vegetation density increased, change in the reflection coefficient of the incident wave was minute whereas wave transmission coefficient and energy loss coefficient tended to decrease.