QUANTIFYING FLOCCULATION SETTLING DYNAMICS OF NATURAL FINE-GRAINED SUSPENDED SEDIMENTS: “FLOCCIN’ ACROSS THE USA!”
Andrew James Manning1, David H Schoellhamer2, Ashish J Mehta3, Geoffrey Schladow4,5, Stephen G Monismith6, Ivy Bifu Huang6, James S Kuwabara7, James L Carter7, Alex Sheremet8, Daniel R Parsons9, Richard J S Whitehouse1, David Todd1, Thomas Benson1 and Jeremy Spearman1, (1)HR Wallingford Ltd, Coasts & Oceans Group, Wallingford, United Kingdom, (2)United States Geological Survey, Portland, OR, United States, (3)Nutech Consultants, Inc., Gainesville, FL, United States, (4)University of California Davis, Civil and Environmental Engineering, Davis, CA, United States, (5)University of California Davis, Tahoe Environmental Research Center, Davis, CA, United States, (6)Stanford University, Dept. of Civil and Environmental Engineering, Stanford, CA, United States, (7)US Geological Survey, Menlo Park, CA, United States, (8)University of Florida, Engineering School of Sustainable Infrastructure & Environment (ESSIE), Gainesville, FL, United States, (9)University of Hull, Energy and Environment Institute, Hull, HU6, United Kingdom
Abstract:
Many coastal and inland waterways are dominated by muddy sediments; typically a mixture of clay minerals and various types of organic matter. When cohesive sediment is entrained into suspension, the particles tend to flocculate. Flocs are less dense, but faster settling than their constituent particles thus affecting their depositional characteristics. As flocs grow, their effective densities generally decrease, but their settling rates rise due to the Stokes’ Law relationship. Flocculation effects become even more complex when purely cohesive sediments are mixed with different ratios of non-cohesive sediments, and if biological activity (e.g., exudate production) affects the resultant cohesion. Developing instrumentation that can provide key physical and dynamical data on depositional rates of flocculating sediments is extremely important in advancing our understanding of natural flocculation processes. Complementary qualitative and quantitative data improve our understanding of the depositional and aggregational physical processes through parameterization.
This presentation will demonstrate recent advances in the study of the flocculation process through the use of video image technology. One such device pioneered at HR Wallingford, and implemented with co-authors, is the high-resolution floc video camera, LabSFLOC - Laboratory Spectral Flocculation Characteristics (developed by Prof. Manning). LabSFLOC can observe (directly or indirectly) floc spectral physical properties, including: floc size, settling velocity, effective density, porosity, shape, mass, and settling flux (using controlled volume referencing). These data are highly desirable for sediment transport modelers. Examples of floc measurements from locations in estuaries, tidal lagoons, river deltas, and lakes from locations across the US will be presented. In addition, we will demonstrate how video floc data can be used to parameterize floc settling characteristics for use in modeling.
