ASSESSMENT OF COASTAL PROTECTION PROVIDED BY SEAGRASS BEACH CAST DEPOSITS: LABORATORY EXPERIMENTS

In coastal areas where seagrass meadows exist, seagrass debris may accumulate forming beach casts called banquettes. There is qualitative evidence that these banquettes may play a role in protecting the beach from erosion and flooding. Nevertheless, there is a lack of studies quantifying this protective role. In this work, large scale laboratory experiments are used to assess the morphodynamic interaction between the beach profile and such banquettes. Results show that if the banquettes are large enough, the part of the beach behind the banquettes is not affected by wave action and remains unchanged. On the contrary, at the toe of the banquettes a greater erosion is observed. The rest of the beach profile behaves similarly to the benchmark (profile without banquette). Smaller banquettes do not show the same protective role and behave more similarly to the benchmark, although they also reduce erosion in the backshore zone.