This study presents the results of LiDAR surveys, spanning 15 years (2002-2017), of the shallow inner sector of Mont-Saint-Michel Bay, a megatidal embayment in Normandy, France, and a UNESCO World Heritage site famous for its monastery. The objective of these surveys was to obtain a better understanding of the morphodynamic processes in this megatidal environment. The campaign has highlighted the circumstances and very short timescales at which changes occur in the channel configuration of the inner bay. It has also been demonstrated the high variability of sediment import and export, which involves not only the tide, but also wind speed and direction. Part of the variability is also related to fluctuations in river discharges into the bay. Since 2009, engineering works have been carried out in the bay. These are aimed at re-establishing the maritime character of the bay around the granite outcrop (Mont-Saint-Michel) on which was built the monastery, and which was increasingly subject to accretion. The main channel of the inner bay shifted recently to a more southward position than observed during the past decades. Yet, from the topographic LiDAR data up to May 2017, it is presently not possible to identify the influence of the engineering works on sedimentation processes beyond a limited zone around the Mont. However, the pursuit of LiDAR surveys is necessary in order to determine whether, in the course of the next decade, the North-South migrations of the Sée-Sélune channel induced by the 18.6 y nodal cycle are affected or not by these works.
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