A sampler-based technique for the study of near-bed sediment dynamics: application in the eastern English Channel

• Published in: Geo-marine letters 2004-05, Vol.24 (2), p.125-132
• Main Authors: Chapalain, G, Thais, L
• Format: Article
• Language: English
• Subjects: Bed load; Current meters; Elevation; Floods; Hydrodynamics; Marine; Samples; Sediments; Shallow water; Suspended sediments; Tidal currents; Vertical distribution
• ISSN: 0276-0460; 1432-1157
• DOI: 10.1007/s00367-004-0170-5

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.