Propriétés hydrodynamiques du mascaret et de son influence sur la dynamique sédimentaire Une approche couplée en canal et in situ (estuaire de la Sée, Baie du Mont Saint Michel)

摘要

The scientific aim of this thesis is to characterize the influence of tidal bore on hydrodynamic, suspended sediment and sedimentary deposits. A double approach has been developed, coupling a study of tidal bores in the Mont-Saint-Michel Bay (MSM) and physical simulation in flume. This work highlights variations of turbulent and viscous stresses associated with significant deceleration phases after the passage of the bore. Our study has remedied the scientific lock to perform measurements in turbulent and highly concentrated flow thanks to a methodological study and to the development of a new sampling tool. Direct measurements in the water column were used to quantify sediment transport crossing the tidal bore and to propose a new model of suspended sediment concentration (SSC) evolution (short and long term) in an estuary submitted to a tidal bore. The model displays a peak of SSC below the front of the bore and a zone of maximum turbidity, never described previously in the bay of MSM. The transport capacity of the tidal bore is confirmed by the wide range of MES grain-size (up to fine sands). The processes involved in erosion and deformation of sedimentary deposits are described (liquefaction and settlement) and highlighted by the results on hydrodynamic processes.