Author(s): Th. K. Koftis; P. Prinos
Linked Author(s): Panagiotis Prinos
Keywords: Seagrasses; P. Oceanica; Wave attenuation; Wave-vegetation interaction
Abstract: Coastal vegetation, such as sea grasses has the following functions regarding hydrodynamic aspects; wave attenuation, protection of the hinterland from wave attack, stabilizing the seabed. In this work an experimental study on wave energy dissipation and velocity structure over Posidonia Oceanica is performed, with P. Oceanica being the most abundant sea grass species in the Mediterranean Sea. Large scale experiments have been conducted in the CIEM flume for irregular intermediate water waves, for the investigation of wave attenuation related to the seagrass characteristics. Results show the efficient wave height attenuation, ranging from 15% -30%, depending on the seagrass characteristics; the seagrass submergence ratio (hs/D, h s=seagrass height, D=water depth) and its density (stems/m2). Wave attenuation increases with increasing plant density and submergence ratio and is obvious for all components of the wave spectra, especially at peak frequencies. Regarding the velocity field, it is shown that the velocities of the longer wave components are mostly attenuated compared to the short wave components. Also the results from the velocities measured at the edge of the seagrass meadow reveal the complicated velocity structure near the edge of the meadow, due to the nonlinear interaction of the wave motion and the movement of the leaves of the seagrasses.
Year: 2011