| Estuarial fine sediments make both positive and negative contributions to the coastal environment and present significant challenges to conservation and management of water resources; yet, tools to predict their transport are seriously deficient.; Aggregation processes dominate fine cohesive sediment transport. This work's objective was to develop an improved fine sediment aggregation processes description based on governing sediment and flow characteristics. A combined statistical and deterministic representation of aggregation processes was combined with the one-dimensional convection-diffusion equation for multiple size classes. The number of two-body and three-body particle collisions was expressed by simple statistical relationships, using a new collision efficiency parameter. Possible collision outcomes were used with collision theory to calculate the rate of sediment mass change for each size class.; Kaolinite and Atchafalaya Bay mud deposition experiments were conducted in a 100-m long flume. Significant variability in measured suspended sediment concentrations can be explained as intermittent perturbation and upward mixing of a high concentration stirred layer flowing close to the bed, below the lowest sampling point.; The calculation method was applied to aggregation chamber and flume experiments. The aggregation processes calculation method was found suitable for use as primary component of sediment transport numerical modeling; but it is computationally intensive.; Experiments showed that the number of three-body collisions in the estuarial environment is small with respect to two-body collisions, but they can contribute significantly to aggregation processes in sediment suspensions. Equilibrium median aggregate size is generally proportional to sediment concentration and inversely proportional to flow shearing rate. Aggregation speed may be either directly or inversely proportional to those two parameters, depending on fluid, flow, and suspension characteristics.; Production-level application of the aggregation calculations will require they be incorporated in a three-dimensional, coupled hydrodynamic and multi-grain-size sediment transport model. The method will provide a significant improvement to the tools available to those charged with conserving and managing water resources where fine sediments constitute a significant challenge. |
