Abstract
Aquatic vegetation provides ecosystem services of great value. Its
protection and restoration has become a major focus in coastal
management. We seek to better understand the role of vegetation in
protecting shorelines from wave energy. The motion of flexible
vegetation blades can significantly reduce the drag force, which will in
turn affect the wave decay. The wave decay can be characterized using an
effective blade length, ππ, which represents the length of a rigid blade
that generates the same wave damping as a flexible blade with length π.
Previous studies suggest that the effective blade length ratio
ππ/π~(πΆππ€πΏ)^β1/4, in which Cauchy number πΆππ€ defines
the ratio of hydrodynamic drag to blade stiffness and the normalized
blade length L is the ratio of blade length to wave orbital excursion.
This laboratory research extends the existing studies and the aim of
finding the link between drag force on an individual blade and wave
dissipation over a meadow. Flume experiments were conducted to measure
the wave decay over an artificial meadow constructed from plastic blades
and wooden dowels. Another set of experiments were conducted to measure
the drag force on the individual blades. Itβs observed that the scaling
law (force on individual blade) is able to predict the wave decay over
the meadow. A correction factor was needed to account for the fact that
the individual blades within the meadow shelter one another. As the stem
density increases, the sheltering becomes more significant, resulting in
a reduced rate of wave energy dissipation.