Morphodynamique des deltas de jusant et des flèches sableuses en domaine macrotidal : les embouchures de l'Orne et de la Dives

Abstract : The aim of this thesis is to understand the mechanisms of sediment bypassing at tidal inlets in a macrotidal environment and the formation of a sandspit with perpendicular hooks. Two closed areas are studied, the Orne and Dives inlets on the coast of Normandy (France). Wave and topographic data, at several space-time scales, are used to study the inlet morphodynamics.The Orne inlet is affected by strong human impacts due to several port facilities whereas the Dives inlet knows a limited anthropogenic impact. The study of the two inlets allows to deduce the impact of the human activities in the sediment transport patterns. The Orne and Dives inlets share the same mechanisms of sediment transport. Both show a major cross-shore component of the transport, underlines by the swash bars migration over the ebb-tidal deltas. All swash bars have similar volumes and migration rates, between 3.5 and 8.0 m/month.The Orne inlet shows deposition on both sides. The accretion on the updrift coast follows the building stages of the harbour of Caen-Ouistreham. On the downdrift coast, the deposition creates the Merville spit, which has several interlocked ridges. A perpendicular hook is present on the distal part of each ridge. This work shows that the swash bar attachment at the shoreline shapes a new ridge. Wave diffraction around the distal part of the swash bars and ridges, and the local wave directions, explain the formation of perpendicular hooks.
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Xavier Pellerin Le Bas. Morphodynamique des deltas de jusant et des flèches sableuses en domaine macrotidal : les embouchures de l'Orne et de la Dives. Sciences de la Terre. Normandie Université, 2018. Français. ⟨NNT : 2018NORMC274⟩. ⟨tel-02163510v2⟩

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