| Three dynamical features associated with estuarine lutoclines are examined with special reference to data from the Jiaojiang estuary in China. These features include turbulence damping induced by high suspended sediment concentration, internal wave behavior at the lutocline, and the response of the lutocline to tidal forcing. It is shown that turbulence damping is governed by the settling flux, cohesion, interaction between flocs and sediment-induced stratification. Maximum turbulence damping in the water column occurs at the lutocline, a finding which supports previous, qualitative observations of a similar nature. Expressions for the vertical momentum and mass diffusion coefficients incorporating these effects have been developed.; Observations from the Jiaojiang are examined for the height, angular frequency, celerity and length of internal waves at the lutocline. Both deep water high and shallow water low frequency waves are identified. The low frequency, at 0.09 rad s−1, is shown to be close to the local Brunt-Väisälä frequency. The high frequency wave, at 1.33 rad s−1, is characterized by sharp crests and flat troughs. The height and the angular frequency of both wave types are shown to decrease with increasing Richardson number.; Lutocline variation with fide in the Jiaojiang is examined by applications of three-dimensional, finite-difference codes developed for flow and sediment transport. It is shown that lutocline response reflect the cumulative effects of sediment settling and entrainment, turbulence damping and tidal asymmetry. |
