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Abstract: For modeling the rate of deposition of cohesive flocs in estuaries the Krone equation is extensively used. It was derived from flume experiments on muddy sediment from the San Francisco Bay, and is applicable to low suspended sediment concentration environments in which shear-induced aggregation – the growth and break up of flocs – has a limited role. It is shown that the use of this equation can lead to erroneous estimates of the mass deposition flux at typically higher estuarine concentrations. Krone's own experimental data permit the development of a more general equation accounting for the effects of concentration and turbulent shear rate on aggregation. These effects are dramatically observed in a deposition test in which a wire mesh was inserted in the flow to change the turbulent shearing rate and increase deposition. Even with the inclusion of aggregation effect in the general equation, field-based observations from San Francisco Bay suggest that typical flumes generally may not meet the space and time scaling requirements for field application of laboratory data. Thus, although the Krone equation should be eschewed in favor of the general equation, interpretations of model-predicted deposition rate must not be accepted without robust field-based verification. [Copyright &y& Elsevier]

Fluid mud is a non-Newtonian slurry of aggregated fine sediment present in numerous bays, estuaries, and lakes. It is a transitory state of mobile mud whose properties are relevant to the definitions and utility of hydrodynamic, acoustic, and, particularly, nautical depth in navigation channels. For estimation of the nautical depth up to which mud must be removed to keep its resistance against vessel propulsion low, processes underpinning fluid mud transport are briefly reviewed. Data from a coastal harbor are revisited to illustrate the role of shear rheometry as an essential component of the method for nautical depth estimation. Broadening the application to channels laden with organic muck often found in many ports, such as those in the southern United States, will require new data and understanding of the biomechanical properties of organic aggregates. Fluid mud dynamics is integral to such efforts. [ABSTRACT FROM AUTHOR]

Sedimentation is examined at a potential site for an oil terminal along the Aoshan channel slope in the vicinity of the East China Sea, where fine-grained sediments predominate. A feature of this slope is that due to characteristically enhanced lateral exchange of fluid momentum and suspended sediment mass, vertical profiles of flow velocity and suspended sediment concentration are more uniform than at the center of the channel. It is shown that lateral eddy diffusion at the slope is likely to be the dominant cause of this mixing. Accordingly, atwo-dimensional, depth-averaged numerical model was applied to simulate historic rates of sedimentation in the study area by using an approximate method to estimate the annual rate of sedimentation, becauselong term data on suspended sediment were unavailable. Model-simulated rates are compared with observed patterns of sedimentation. [ABSTRACT FROM AUTHOR]