Article Dans Une Revue CONTINENTAL SHELF RESEARCH Année : 2024

Morphodynamics of two Mediterranean microtidal beaches presenting permanent megacusps under the influence of waves and strong offshore winds

Résumé

This study focuses on four years of survey of two low-microtidal emerged beaches (average tidal range ≈ 0.3 m), presenting permanent megacusps on the French Mediterranean coast. These beaches are representative of the southern part of the Gulf of Lion (45 km of coast): the Leucate beach backed by a small dune and the La Franqui beach backed by a small lagoon. An analysis of the hydrodynamic and meteorological forcing along with morphological changes allows to define the key parameters controlling the system. These results are used to develop a conceptual model composed of five main situations and then compare it to the microtidal literature. Dominant offshore winds can reach speeds of up to 20 m s-1 (Gusts up to 30 m s-1) and have an erosive action on the backshore and produce advance of the shoreline of a few metres. This shoreline advance is mainly concentrated on the horns when it is concomitant with small fair-weather waves. Waves of moderate to high intensity (storms) lead to strong erosion and steepening of the beach face, as well as the migration or construction of a new higher berm located landward and associated with sediment deposition on the upper beach. The low tidal range may also allow the high run-up level to stabilise for a longer period of time in a high elevation on the backshore. The alternation of storm episodes and offshore wind periods could control the relative stability of the emerged beach.
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insu-04729601 , version 1 (16-01-2025)

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Pierre Feyssat, Raphaël Certain, Nicolas Robin, Jean-Paul Barusseau, Antoine Lamy, et al.. Morphodynamics of two Mediterranean microtidal beaches presenting permanent megacusps under the influence of waves and strong offshore winds. CONTINENTAL SHELF RESEARCH, 2024, 272, ⟨10.1016/j.csr.2023.105160⟩. ⟨insu-04729601⟩
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