Sediment Budget Implications from Posidonia oceanica Banquette Removal in a Starved Beach System

This study discusses the potential impact of removing Posidonia banquette on the sediment budget of a siliciclastic-sediment-starved beach-barrier system. The morphology as well as the sediment volumes of this system were estimated. The banquette’s composition and sediment content were determined with samples collected during five sampling campaigns conducted in one year. The carbonate content of the system was estimated by analyzing three 1 m long cores collected along the barrier. Five digital terrain models from DGPS surveys were used to compute the beach’s average morphology to estimate the sediment volumes. The carbonate and siliciclastic sediment content from the cores were used to calculate the overall beach’s sediment mass. Total sediment mass accounted for 126,000 m3, of which ca. 86% was siliciclastic quartz sand and approximately 14% was carbonate sediment. Total banquette deposition during the year accounted for 2300 m3, with a maximum and averaged sediment content of 339 kg m3 and 78 kg m−3. A permanent loss of ca. 1.31% of total mass will occur if 5000 m3 of banquette were to be removed. In such beach settings, banquette removal may limit sediment availability, reducing the overall sediment mass and decreasing beach resilience against climate change effects such as sea level rise.