Wave interaction with flexible vegetation: connecting individual blade dynamics to meadow scale wave decay

Flexible plants move in response to wave orbital velocity, which diminishes wave decay relative to rigid plants. The impact of reconfiguration and blade motion on wave decay has been characterized using an effective blade length, l_e, which represents the length of a rigid blade that generates the same drag as the flexible blade of length l. The effective blade length depends on the Cauchy number, which represents the ratio of hydrodynamic drag to blade stiffness, and on the ratio of blade length to wave orbital excursion. This laboratory study considered how scaling laws determined for individual blades could be used to predict the wave decay over a meadow of multiple plants. First, the drag force on and motion of individual model blades was studied for a range of wave conditions to provide empirical coefficients for the theoretically determined scaling laws for effective blade length, l_e . Second, the effective blade length predicted for individual blades was incorporated into a meadow-scale model to predict wave decay over a meadow. Third, wave decay was measured over meadows of different plant density (shoots per bed area), and the measured decay was used to validate the wave-decay model.