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Setting of atypical marine sandwaves by rotary currents: impact of island and shoal, Ecrehou archipelago, in the local modification of tidal currents (Channel Islands, France)
Garnaud, S.; Ehrhold, A.; Garland, Th.; Trentesaux, A. (2000). Setting of atypical marine sandwaves by rotary currents: impact of island and shoal, Ecrehou archipelago, in the local modification of tidal currents (Channel Islands, France), in: Trentesaux, A. et al. Marine Sandwave Dynamics, International Workshop, March 23-24 2000, University of Lille 1, France. Proceedings.
In: Trentesaux, A.; Garlan, T. (Ed.) (2000). Marine Sandwave Dynamics, International Workshop, March 23-24 2000, University of Lille 1, France. Proceedings. Université de Lille 1: Lille. ISBN 2-11-088263-8. 240 pp., more
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Document type: Conference paper
Keyword
    Marine/Coastal
Authors  Top 
  • Garnaud, S.
  • Ehrhold, A.
  • Garland, Th.
  • Trentesaux, A.
Abstract
    SHOM (Service Hydrographique et Océanographique de Marine) realised many hydrographic surveys in the Deroute Channel between the Cape of La Hague and Chausey Islands since 1993, to open a new navigable way for the ferries. Three detailed surveys in the strait between Jersey and the French coast (Cotentin) have been carried out using single and multibeam bathymetry and side-scan sonar. The seafloor is characterized by large sandwaves that are good examples of mega-structures. These structures are associated with a shoal affected by strong tidal currents, this was often observed in the English Channel. Geometry of Ecrehou Archipelago and Ecrevière bank provides a complex sedimentary dynamic that generates an atypic pattern of sandwaves in this area. This large dune field, located southeast Ecrehou Archipelago, is composed of active sandwaves. The evolution of the bathymetry can be studied at different time scales: the results are supported by three surveys in 1998 and a 1939. A tidal numerical model applied in the area between Jersey and Cotentin shows anticlockwise and clockwise cells of sedimentary circulation around Ecrehou Archipelago. The existence of anticlockwise rotary current on large dune field explicates symmetrical sandwaves that are oriented north/south. The dynamic that controls construction and stability of asymmetrical sandwaves (NW/SE) is mainly governed by tidal currents.
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