Effects of floc strength on viscosity and deposition of cohesive sediment suspensions

The hydrodynamic properties of cohesive sediment flocs in tidal waters and the resulting sediment transport depend on the strength of the flocs. Using the concept of self-similar floc structure, estimates of floc strength are obtained from observed maximum sizes of settling flocs and from rheological data. Three applications are discussed: a model of the shear-rate dependent viscosity of a high-concentration cohesive sediment suspension, a theoretical expression for the critical bed shear stress for deposition on a smooth bed, and the breakup of flocs upon deposition in still water including the associated increase in excess floc density. Model results are compared with observations reported in the literature.