HR: 14:20h
AN: OS52F-02    [PDF]
TI: Net flux and deposition of sediment by tidal currents in a macrotidal estuary
AU: * Jago, C F
EM: c.f.jago@bangor.ac.uk
AF: School of Ocean Sciences, University of Wales Bangor, Marine Science Laboratories, Menai Bridge, LL59 5AB United Kingdom
AU: Jones, S E
EM: oss046@bangor.ac.uk
AF: School of Ocean Sciences, University of Wales Bangor, Marine Science Laboratories, Menai Bridge, LL59 5AB United Kingdom
AU: Reid, G S
EM: g.reid@bangor.ac.uk
AF: School of Ocean Sciences, University of Wales Bangor, Marine Science Laboratories, Menai Bridge, LL59 5AB United Kingdom
AB: Measurement of net sediment transport in estuaries is difficult because of the scale of measurement errors. However, a successful experiment is described here. The experiment was conducted in a sandy, macrotidal estuary where fast tidal currents move sand predominantly in suspension. The sediment budget is known from levelling surveys over the period 1968-present which give an annual sedimentation rate of 0.020 m/yr. Mineralogical evidence proves an offshore source for the sediment. Sediment fluxes were measured through cross sections of the estuary over tidal cycles using transmissometers for suspended sediment concentration. Because of time-velocity asymmetry on spring tides, flood sediment flux exceeds ebb sediment flux. By relating measured sediment fluxes to tidal range, gross and net annual fluxes have been computed. The extrapolated net sedimentation rate, due only to tides, is 0.014 +/- 0.036 m/yr, which is close to the rate determined by levelling on decadal time scales. This result shows that contributions to net sediment transport from river flow and waves are small, and that, under favourable circumstances, long-term flux estimates can be derived from short-term measurements.
DE: 4546 Nearshore processes
DE: 4558 Sediment transport
DE: 4863 Sedimentation
SC: Ocean Sciences [OS]
MN: 2004 Ocean Sciences Meeting