| Observations of fair weather currents and suspended sediment concentrations
(SSC) were made using an acoustic Doppler current profiler and two YSI turbidity sensors over
a neap to spring time cycle at a site near the inner mouth of a semi-enclosed
mesotidal-macrotidal embayment (Jiaozhou Bay) to examine the influence of tidal dynamics on
concentration and transport of suspended sediment. During the investigation, SSC varied from
about 3 to 16 mg L–1 at the surface and about 6 to 40 mg L–1 close to
the bed, while the current
velocity reached 79 cm s–1 at the surface and 61 cm s–1 near the bed.
SSC was tidally cyclic. The near-bed instantaneous SSC was closely related to current velocity
with almost no time lag, indicating that the variability of SSC was governed by current-induced
settling/resuspension. At the surface, however, instantaneous SSC was poorly related to
instantaneous current velocity because the peak SSC tended to occur around ebb slack water.
This suggests that the surface SSC was controlled by horizontal advection from landward higher
concentration areas. Both at the surface and near the bed, on the other hand, tidally-averaged
SSC was well correlated to tidal range and current speed. Current velocity and SSC were
flood-dominated for all the tides investigated, which resulted in significant landward residual
suspended sediment transport at the study site. The observed flood dominance was mainly
attributed to the location of the study site on the landward side of the bay’s inlet where
flow separation is favoured during flood tide. It was concluded that tides are the dominant
hydrodynamic component controlling the variability of SSC during fair weather at the study
area.
Keywords: sediment, concentration, suspension, advection, currents, shoalling effect,
Jiaozhou Bay, China |