A sampler-based technique for the study of near-bed sediment dynamics: application in the eastern English Channel |
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| Authors: | Email author" target="_blank">Georges?ChapalainEmail author Laurent?Thais |
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| Institution: | (1) UMR-CNRS 8110 Processus & Bilans en Domaines Sédimentaires, Bâtiment SN5, Université des Sciences et Technologies de Lille, 59655 Villeneuve d Ascq, France;(2) UMR-CNRS 8107 Laboratoire de Mécanique de Lille, Université des Sciences et Technologies de Lille, PolytechLille, 59655 Villeneuve dAscq, France;(3) Present address: UMR-CNRS 6539 LEMAR, Institut Universitaire Européen de la Mer (IUEM), Technopôle Brest-Iroise, Place Nicolas Copernic, 29280 Plouzane, France |
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| Abstract: | 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. |
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