Field Observations of Cohesive Sediment Flocculation in a Partially Stratified Estuary

This research is focused on understanding cohesive sediment dynamics and transport in a partially stratified estuary. Tidal variability in floc size distribution and its physical controls are examined using continuous depth-profiles from a 48-hr stationary experiment in the upper San Francisco Bay estuary. Median floc sizes were correlated with three estimates of turbulent dissipation obtained using a vertical microstructure profiler, a boat-mounted acoustic Doppler current profiler, and law-of-the-wall analysis. The results suggest that flow is the most dominant control on floc size as compared to salinity, organic content, and suspended sediment concentration. Relationship between floc size and light penetration were also quantified, and we showed that smaller flocs are better at scattering light. The overall goal of this research is to provide a better physical understanding of flocculation dynamics and its interplay with estuarine turbulence and in-water light availability.