Influence of the 18.6-year lunar nodal tidal cycle on tidal flats: Mont-Saint-Michel Bay, France

• Published in: Marine geology Vol. 387; pp. 108 - 113
• Main Authors: Levoy, F., Anthony, E.J., Dronkers, J., Monfort, O., Izabel, G., Larsonneur, C.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.05.2017; Elsevier
• Subjects: 18.6-year tidal cycle; Macrotidal bay; Mont-Saint-Michel Bay; Physics; Sciences of the Universe; Tidal channel migration; Tidal flats; Macrotidal bay; Mont-Saint-Michel Bay; Tidal channel migration; 18.6-year tidal cycle; Tidal flats
• ISSN: 0025-3227; 1872-6151
• DOI: 10.1016/j.margeo.2017.03.009

The influence of the 18.6-year nodal tidal cycle on estuarine accretion, and indirectly on channel migration patterns, in Mont-Saint-Michel Bay, a UNESCO World Heritage Site famous for its monastery, is explored over three tidal cycles from a 68-year dataset that combines aerial photographs (1947–2007), one DGPS survey (1997), and nine LiDAR Digital Elevation Models (2002–2015). Sand-flat elevation and sediment-budget changes in this megatidal environment were further determined over the last nodal cycle using DGPS and LiDAR surveys. We infer that the changes observed are linked to variations in tidal prism and current velocities in this shallow, large tide-range setting. Increasing (rising tidal range) or decreasing (falling tidal range) flood-dominated asymmetry are deemed to lead, respectively, to waxing and waning of sediment import, in the form of large sand banks, into the bay over the 18.6-year nodal tidal cycle that, in turn, force channel migration. Coriolis acceleration and centrifugal forces are also considered to contribute to the observed channel migration. •The 18.6-year tidal cycle influence on a large macrotidal embayment is studied.•Aerial photographs and LiDAR data on at least 3 tidal cycles are used.•The mobility of the main channels is strongly influenced by this lunar cycle.•Elevation changes and sediment budget are also linked to the tidal cycle phases.•Changes in tidal prism and flood-dominant tidal asymmetry drive the bay infill.