Evolution of a Shelly Beach Ridge System over the Last Decades in a Hypertidal Open-coast Embayment (Western Mont-Saint-Michel Bay, NW France)

A dynamic shelly beach ridge system along the southern coast of Mont-Saint-Michel Bay, NW France, exhibits alternating erosion and accretion patterns influenced by tidal cycles and human activities. The study reveals that these ridges, formed from mollusk shells, are more prominent in erosional bands shaped by wave and current dynamics, potentially driven by shellfish farms, tidal channels, and reefs. Decadal-scale behavior is linked to the 18.6-year nodal tidal cycle, with periods of landward migration during peaks and stability at troughs, further complicated by storm events. Notably, no beach ridges older than the 19th century survive in front of the Medieval dike, suggesting reworking due to Little Ice Age storminess. Shellfish farming has also stabilized the system by altering shell composition. The research combines aerial photographs (1947–present), sediment cores, ground-penetrating radar, and digital elevation models to unravel these processes.

Tessier, B., Poirier, C., Weill, P., Dezileau, L., Rieux, A., Mouazé, D., Fournier, J., & Bonnot-Courtois, C. (2019). Evolution of a Shelly Beach Ridge System over the Last Decades in a Hypertidal Open-coast Embayment (Western Mont-Saint-Michel Bay, NW France). Journal of Coastal Research, 88(sp1), 77. https://doi.org/10.2112/si88-007.1