The discharge of 7 million cubic meter of dredged material in the LOIREestuary took place in 1977 during the creation of the methane terminal channel Thisdischarge was preceeded by a multidisciplinary survey conducted 50 as to ide ntif y and comply with the various conditions for the preservation of the environment (lateral muddy bank) : evolution of sedimentation, current studies hydrosedimentary survey on a scale model, study by radioactive tracers, stability of the banks, inventory of benthos, After discharge of the material, a program was conducted ta monitor the evolution of the area up ta the present time, so as ta evaluate the positive and negative consequences. Globally, the policy implemented in the LO/RE can serve os a model for the discharge of dredged materia/ inside estuaries : hydraufic regulaiion of ihese areas by formation of islands. L PRESENTATION GENERALE DU SITE L'étude des remblais hydrauliques en estuaire que nous examinons se situe dons la partie aval de l'eSTuairede la LOIRE(Fig. 1). Cette zone a toujours constitué la section de la Loire la plus difficile à régulariser: entre le goulet d'étranglement Saint-Nazaire-Mindin et le goulet des Brillantes-Moutons, le fleuve présente une surlorgeur très importante, provoquant des phénomènes hydrauliques et sédimentologiques particuliers De nombreux bancs de sable émergeant et divaguant l'encombraient, créant une géne considérable pour la navigation.
Chemical composition and physical parameters of waters from the Loire estuary were examined in 1981-1982 in order to assess water quality. It appears that riverflow is of first importance on suspended matter load, dissolved nutrient concentrations and oxygenation. The annual hydrological cycle is made of two periods. During the first one low riverflow, low nutrient concentrations, high suspended matter load and oxygen depletion are noticed. During the second one higher riverflows occur accompanied with increasing nutrient concentrations, decreasing turbidity and restoration of dissolved oxygen. Results indicate that annual inputs of dissolved nutrients attain 60 000 t a-I for nitrogen, 2 400 t a-I for phosphorus and 100 000 t a-I for silica. It is suggested that the high suspended matter loading (I million t a-I) is a significant factor disturbing oxygenation and by the way limiting water quality within the estuary.
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