Morphodynamique du littoral de Mayotte - Des processus au réseau de surveillance.

Abstract : Mayotte Island, located in the Mozambique Channel, western Indian Ocean, is characterised by a vast, highly diversified reef-lagoon complex comprising significant mangrove development. Several field experiments involving hydrodynamic measurements, topographic surveys, and observations were coupled with the analysis of aerial photographs and the collation of regional meteorological data in order to gain a better understanding of the evolution of the reef-lagoon complex and of the morphodynamic interactions between the mangroves and the coral reefs. The results highlight a remarkably variable mangrove system subject to progression or stability in the north and east of the island, but exhibiting a clearly regressive pattern along the southern and western shores. The hydrodynamic data acquired during the field experiments clearly bring out the spatial and temporal variations in wave and mean current patterns involved in these differences. These data also throw light on the short-term morphodynamics of the small pocket beaches associated with some of these mangroves. The degree of exposure to waves, and reef structure, notably in terms of width and elevation relative to the tidal frame, have a determining influence on the afore-mentioned variations in mangrove dynamics along the shores of the island, and in the greater vulnerability of the mangrove shores of the south and west of the island, especially in the face of strong impinging development pressures. The extermination of these mangrove systems leads to a reorganisation of the sediment stocks and the emergence of new shoreline morphodynamic patterns. These changes have necessitated the construction of an operational observatory aimed at monitoring the coastal dynamics. This tool is based on a network sourced by the measurements and field observations integrated into a GIS. Within a local framework of strong socio-economic and demographic pressures, and a more global context of environmental change, this observatory should lead to a better understanding and prediction of the morphodynamics of the shores of Mayotte, while providing data indispensable to stakeholders involved in decision-making in the face of the major and rapid environmental and socio-economic changes liable to affect the fragile reef-mangrove coastal systems
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Matthieu Jeanson. Morphodynamique du littoral de Mayotte - Des processus au réseau de surveillance.. Océan, Atmosphère. Université du Littoral Côte d'Opale, 2009. Français. ⟨tel-00449987⟩

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