Collaborative Research: The Role of Flocculent Organic Sediment Transport as a Feedback Mechanism that Controls Landscape Dynamics and Restoration Success in the Everglades

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The proposed research tests the hypothesis that sediment transport dynamics play a role incontrolling the topographic patterning that is crucial to the ecology of the ridge and slough landscape inthe Florida Everglades. Namely, under historical flow conditions, it is hypothesized that sedimentredistribution from open-water slough to vegetated ridge regulated ridge width but that, with drainage andcompartmentalization of the Everglades, the magnitude of redistribution has decreased, permittingexpansion of ridges into open-water sloughs and loss of topographic heterogeneity.Project hypotheses will be tested through a combination of field and laboratory experimentationand numerical modeling of the mass and momentum balance equations governing flocculent sedimenttransport dynamics and flow in vegetated environments. Experimental analysis of floc transportmechanics will describe the critical shear stresses and turbulence intensities that entrain size classes offloc in a deposited bed, equilibrium aggregate size distributions and concentrations resulting from flowwith different shear parameters, aggregate settling velocities, and changes in turbulence and flow profilesthat occur across a ridge/slough cross-section as a result of vegetation and microtopography. To this end,flow monitoring and a series of transport experiments and tracer tests using natural floc will be performedin laboratory and field flumes. Funds will also sponsor the execution of complementary science fairprojects by Forest Hill High School environmental science magnet program students, which will focus onusing a rapid-assessment optical technique for developing an organic matter mixing model across aridge/slough transect (which can be used as a validation measure for the sediment transport model) and onelucidating the effects of ambient water quality on flocculent organic sediment transport properties.Intellectual merit. The proposed research builds upon previous research showing the existence ofsediment redistribution from open-water channels to vegetated environments by producing a model topredict the magnitude and spatial distribution of sedimentation as a function of flow velocity and waterlevel. In the Everglades, sediment occurs primarily in the form of organic floccules, the mechanics ofwhich are not well understood. Similarly, although flocculation plays a dominant role in the suspendedsediment dynamics of rivers, wetlands, and estuaries throughout the world, studies on the impacts of flowthrough vegetated environments on sedimentation and transport of floccules and predictive models of flocdynamics on landscape morphology and evolution are nonexistent. This research develops a set oflaboratory and field experiments designed to address the critical questions about floc transport mechanicsrequired for model development and an original model of how these mechanics influence landscapeevolution. Thus, the proposed research will set a precedent for improved predictions of sedimenttransport and landscape dynamics that will have implications for estuarine science, fluvialgeomorphology, wetlands science, and contaminant transport.Broader impacts - Results of this project will be broadly disseminated to (1) researchers in the field,through organization of a special session at an ASLO meeting on implications of flocculant sedimenttransport for landscape dynamics and subsequent publication of a special journal issue, to (2) policymakers involved in implementation of the Comprehensive Everglades Restoration Plan through regularparticipation of the PIs in Landscape Subteam meetings and the Greater Everglades EcosystemRestoration conference, and to (3) the general public, through publication of a popular science article onEverglades landscape dynamics. Further, model results will impact policy and society by leading toimproved recommendations of flow velocities and hydroperiods that should be implemented to restore theridge and slough landscape. Enhanced infrastructure resulting from the purchase of a laser diffractionparticle size analyzer will benefit classroom demonstrations, laboratory, and field research at the K-12,undergraduate, and graduate levels. Research efforts will also enhance collaborative efforts between theUSGS, University of Colorado, and K-12 education and will synergistically complement an existingUSGS project on biogeochemical feedback mechanisms and nutrient transport within the ridge and sloughlandscape. Finally, this research enhances the knowledge transfer to future generations of scientiststhrough a committed partnership with the environmental science magnet program at Forest Hill HighSchool in West Palm Beach, Florida and by providing research support to a current Ph.D student.