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A sampler-based techniquefor the study of near-bed sediment dynamics : application in the Eastern English Channel

type de publication      article dans une revue internationale avec comité de lecture
date de publication 2004
auteur(s) Chapalain Georges; Thais Laurent
journal (abréviation) Geo-Marine Letters (Geo Mar Lett)
volume (numéro) 24(2)
  
pages 125 – 132
résumé A simple technique for studying near-bed hydrodynamics and sediment dynamics is presented. The method combines the use of (1) a benthic tripod hosting a series of electromagnetic current meters, and (2) a newly developed near-bed multi-level water-sediment mixture sampler. The instrument package was deployed successfully at a shallow water station in the eastern English Channel. The currents at elevation 0.9 m above the bottom were asymmetrical, the flood current peak being slightly stronger than the ebb current peak. At elevation 0.3 m above the bottom, the ebb/flood current peak asymmetry vanished. The observed SSCs (suspended sediment concentrations) were tidally modulated, with a contrasting vertical distribution over the ebb and flood phases of the tidal current: the profile was uniform in the ebb phase whereas a stratification appeared in the flood phase. The depth dependence and time evolution of the SSCs are attributable to a combination of local resuspension and advection-dispersion of remotely suspended fine sediment by ebb currents. Suspended sediment fluxes were uniform during the ebb phase and increased with elevation above the bottom during the flood phase.
mots clés hydrodynamics sediment dynamics
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