The proposed research tests the hypothesis that sediment transport dynamics play a role in controlling the topographic patterning that is crucial to the ecology of the ridge and slough landscape in the Florida Everglades. Namely, under historical flow conditions, it is hypothesized that sediment redistribution from open-water slough to vegetated ridge regulated ridge width but that, with drainage and compartmentalization of the Everglades, the magnitude of redistribution has decreased, permitting expansion of ridges into open-water sloughs and loss of topographic heterogeneity. Project hypotheses will be tested through a combination of field and laboratory experimentation and numerical modeling of the mass and momentum balance equations governing flocculent sediment transport dynamics and flow in vegetated environments. Experimental analysis of floc transport mechanics will describe the critical shear stresses and turbulence intensities that entrain size classes of floc in a deposited bed, equilibrium aggregate size distributions and concentrations resulting from flow with different shear parameters, aggregate settling velocities, and changes in turbulence and flow profiles that 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 performed in laboratory and field flumes. Funds will also sponsor the execution of complementary science fair projects by Forest Hill High School environmental science magnet program students, which will focus on using a rapid-assessment optical technique for developing an organic matter mixing model across a ridge/slough transect (which can be used as a validation measure for the sediment transport model) and on elucidating the effects of ambient water quality on flocculent organic sediment transport properties. Intellectual merit. The proposed research builds upon previous research showing the existence of sediment redistribution from open-water channels to vegetated environments by producing a model to predict the magnitude and spatial distribution of sedimentation as a function of flow velocity and water level. In the Everglades, sediment occurs primarily in the form of organic floccules, the mechanics of which are not well understood. Similarly, although flocculation plays a dominant role in the suspended sediment dynamics of rivers, wetlands, and estuaries throughout the world, studies on the impacts of flow through vegetated environments on sedimentation and transport of floccules and predictive models of floc dynamics on landscape morphology and evolution are nonexistent. This research develops a set of laboratory and field experiments designed to address the critical questions about floc transport mechanics required for model development and an original model of how these mechanics influence landscape evolution. Thus, the proposed research will set a precedent for improved predictions of sediment transport and landscape dynamics that will have implications for estuarine science, fluvial geomorphology, 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 sediment transport for landscape dynamics and subsequent publication of a special journal issue, to (2) policy makers involved in implementation of the Comprehensive Everglades Restoration Plan through regular participation of the PIs in Landscape Subteam meetings and the Greater Everglades Ecosystem Restoration conference, and to (3) the general public, through publication of a popular science article on Everglades landscape dynamics. Further, model results will impact policy and society by leading to improved recommendations of flow velocities and hydroperiods that should be implemented to restore the ridge and slough landscape. Enhanced infrastructure resulting from the purchase of a laser diffraction particle 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 the USGS, University of Colorado, and K-12 education and will synergistically complement an existing USGS project on biogeochemical feedback mechanisms and nutrient transport within the ridge and slough landscape. Finally, this research enhances the knowledge transfer to future generations of scientists through a committed partnership with the environmental science magnet program at Forest Hill High School in West Palm Beach, Florida and by providing research support to a current Ph.D student.
