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TitreBay of Fundy bedform mapping: linking geomorphology with sediment transport models
AuteurTodd, B J; Li, M Z; Shaw, J; Prescott, R
SourceGeoHab 2010, characterisation, quantification and diversity of extreme habitats, conference handbook, programme & abstracts; par Lamarche, G (éd.); 2010 p. 143
LiensOnline - En ligne
Séries alt.Secteur des sciences de la Terre, Contribution externe 20090415
RéunionGeoHab 10th International Conference; Wellington; NZ; mai 4-7, 2010
Mediapapier; en ligne; numérique
ProvinceRégion extracotière de l'est
Lat/Long OENS-67.5000 -64.5000 45.5000 44.2500
Sujetsconfigurations lit; déplacement de la configuration lit; topographie du fond océanique; topographie du fond océanique; transport sous-marin; transport des sediments; géologie marine; géologie des dépôts meubles/géomorphologie
ProgrammeÉnergie renouvelable offshore, Géoscience en mer
Résumé(disponible en anglais seulement)
The Bay of Fundy on the Atlantic coast of Canada has the largest tidal range in the world, reaching 17 m. Associated tidal current velocities exceeding 5 m s-1 are being exploited during 2009 - 2011 for engineering tests of turbines placed on the seabed for in-stream tidal electrical power generation. If successful, these turbine tests may lead to future installation of a full-scale tidal power system (~300 turbines) on the seafloor of the bay. Understanding the regional surficial geology is necessary for predicting sediment mobility and implications of that mobility for the design of seabed infrastructure and environmental impact in the region. In anticipation of tidal power development, the Geological Survey of Canada instituted in 2006 a regional program to map the sea floor of the Bay of Fundy (13,000 km2) using multibeam sonar and geophysical and geological groundtruth techniques. Interpretation has revealed that the Bay of Fundy is floored by widespread glacial deposits (till) of Wisconsinan age, 10 to 30 m thick, overlying Triassic - Jurassic bedrock. In some areas, deep channels have been eroded in glacial sediment, presumably through the action of tidal currents. Superimposed on the glacial sediments are Holocene sediments in the form of discrete sand waves up to 20 m high, fields of sand waves, and large banner banks flanking prominent headlands around the bay. Gravel megaripples occur in Minas Passage, the main erosional channel.
Tidal current data, circulation and storm driven current data, and wave information were coupled with sediment grain size data within the sediment transport model SEDTRANS. The model computed sediment transport flux and bottom shear stress. The latter was compared to bedload threshold shear stress to determine the sediment mobility frequency, or the time percentage of bedload threshold was exceeded by various processes. Sediment mobilization is dominated by the tides, reaching 30% over most of the bay and 100% in some areas. Both the maximum seabed disturbance and maximum sediment mobility occurs in Minas Passage, which is the location of in-stream tidal device deployment. Modelled tidal flow and sediment transport patterns in the Bay of Fundy clearly reflect the distribution and geomorphology of the sand bedforms. Sediment dynamics will be measured using in situ instrumentation. The interpretation of the sediment mobility observations and modelling will provide information necessary for informing government management decisions regarding the use of the Bay of Fundy seabed for in-stream tidal power projects and for other competing seabed uses.