On the wave attenuation properties of seagrass meadows

The wave attenuation properties of seagrass meadows were investigated in a flume facility using dynamically-scaled models of seagrass exposed to regular long crested waves. Experiments were conducted for 66 wave conditions and with four plant densities; waves were measured with eight resistance wave gauges. The data collected represent the most-comprehensive dataset of its kind. They reveal that the wave attenuation coefficient KD of a seagrass meadow reaches a uniform value after a distance of approximately 1.5–3 times the water depth from the meadow start and that both KD and the drag coefficient Cd depend significantly on the plant density. An improved model of KD based on the work of Lei and Nepf (2019) is proposed that takes into account the effects of the solid volume fraction of the plant model through a correction on Cd and that of plant density via an effective vegetation frontal area av−e. The effective vegetation frontal area is described as a power law of the roughness density λf. The model, which was validated with the data of KD obtained from the laboratory experiments described herein, displays an excellent agreement with data from the literature. It can predict KD accurately also for cases whereby the maximum wave orbital excursion is comparable with the blade length, despite this condition violates the model's assumptions. This work provides a comprehensive dataset and a new model that can be used to improve the prediction of wave attenuation of seagrass meadows.