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Gregory Noe; Raymond Schaffranek (retired)
Our proposed experiments and modeling are fundamental to building a reliable predictive capability of how the Everglades will respond to the restorationís higher flows.
Additional scientific questions that must be answered to support The Water Conservation Area 3A Decompartmentalization and Sheet Flow Enhancement Project (DECOMP) include:
1. How do the characteristic ridge and slough topographic variation and its associated vegetation patterns influence the sources, transport rates, rates of interception, and storage residence times of suspended particulates and nutrients? 2. What are relative roles of transport of fine suspended particulate matter and coarser flocculent benthic organic matter (floc) in suspended sediment and phosphorus budgets in Everglades wetlands? 3. To what extent will sources, concentrations, and transport distances of suspended sediments and nutrients in Everglades wetlands be altered by DECOMP? Will increased sheet flow velocities or the extent of canal backfilling after levee removal be the more important driver of changes in transport? 4. What flow velocities are necessary to entrain and redistribute sediment in the ridge and slough landscape?
Saiers, J. E.; Newlin, J. T.
accessed as of 4/26/2011
Harvey, Judson W.; Mylon, Steven E.
accessed as of 4/26/2011
Childers, Daniels L.
accessed as of 4/26/2011
Harvey, J. W.; Saiers, J. E.
Saiers, J. E.; Harvey, J. W.; Noe, G. B.; Mylon, S.
Riscassi, Ami L.
McCormick, Paul V.
The article was originally published in the Hydrogeology Journal.
Schaffranek, Raymond W.; Noe, Gregory B.; Larsen, Laurel G.; Nowacki, Daniel J.; O'Connor, Ben L.
Harvey, Judson W.; Crimaldi, John P.
Harvey, Judson W.; Noe, Gregory B.; Crimaldi, John P.
Up to now our team has focused its experimental research at two research sites: northern Shark Slough, and more recently, at site 3A-5 in north central Water Conservation Area 3A, an area that has proved to be an excellent "reference" site for measuring transport rates and processes in remnant conditions where ridge and slough topography is relatively well preserved. This research is providing perspective on pre-drainage conditions which is critical to understanding the flow-topography-sediment interactions that occurred in the historic flow regime and topography of the Everglades. Among our accomplishments is developing the techniques that will be applied in the near future to characterize flow and transport conditions in areas possessing more degraded landscape characteristics.
Starting in FY08 our investigations of "reference" conditions at our WCA-3A-5 will be supplemented by adding "first response" research sites in WCA-3B, where we will have the ability to test our predictions within the framework of the Decompartmentalization Physical Modelís (DPM) landscape-scale manipulation of sheet flow in an area of degraded landscape characteristics. Those sites will possess substantially degraded ridge and slough topography and will be located downstream of where substantial levee removal is expected to take place (i.e., WCA-3B). Preliminary planning is already underway for the DPM, a long-term, landscape-scale experiment. The overall purpose of DPM is to test hydrologic and ecosystem-level responses to opening of large gaps in levees and filling of canals at a large but manageable experimental scale. The USGS role will be to conduct the experimental and modeling work to assess how increased sheetflow across various levels of levee removal and canal backfill designs perform in terms of transport of sediments and associated nutrients to downstream areas. A 3-year test period is planned which will not only reveal the first response characteristics of levee removal and increased sheetflow, but which will establish the sites and protocols for further evaluation in later years to assess the long term geomorphic and ecosystem-level changes that can be expected over a large proportion of the central Everglades after DECOMP is fully implemented
After first developing our tracer experimental methods in Shark Slough (Saiers and others, 2003; Harvey and others, 2005) and our methods for suspended particle sampling in a cross-system comparison of the Water Conservation Areas and Everglades National Park (Noe and others, 2007), we have most recently focused our attention on measuring flow and sediment transport in the ridge and slough environments of Water Conservation Area 3 as they relate to flow velocity, vegetation type and density, and sources of water to WCA3 (e.g. precipitation and structure inflows). Modeling is underway to interpret the controlling processes on velocity and shear stress as they differ within ridge and slough plant communities (Harvey and others and Larsen and others, in preparation) and effects of flow, meteorological conditions, and vegetation communities on suspended particle abundance, sources, size distribution, and phosphorus content (Noe and others, in preparation)
In FY08 we will build upon our previous work by quantifying the entrainment, transport, biogeochemistry, and sources of suspended particles under a range of experimental flow velocities. The most important improvement in the planned experiments is the use of an underwater camera and a Sequoia Scientific LISST-100X laser diffraction particle size analyzer (LISST-100x) to detect movement of natural suspended particulates rather than the fluorescent or mineral "model" particles that we introduced in previous experiments with our Yale University colleagues (Saiers and others, 2003; Huang and others, 2008). Use of natural particles in these experiments is essential to reliably characterize "entrainment" of suspended particulates under the naturally complex conditions of mixed particle sizes that arise from several different sources of organic matter (e.g., fine suspended vs. coarse floc). Of particular importance is determining the threshold conditions of sheetflow velocity and bed shear stress that cause entrainment of floc, and determining whether and under what flow conditions those particles will experience a net redistribution from slough to ridge. We will also test the ability of spectral analysis of suspended material and other ecosystem components (floc, peat, different forms of periphyton, macrophytes) to identify the source(s) of suspended material under the different experimental flow velocities in ridge and slough. Visible and near-infrared reflectance spesctroscopy has been used to differentiate plant communities in the Everglades for remote sensing (John Jones, USGS, personal communication) and to assess wetland soil characteristics in general (Cohen and others, 2005). We will conduct preliminary sampling to evaluate the ability of this method to distinguish the potential sources of particles and develop spectral source mixing models for suspended particles, and then possibly apply the method in the flow experiments. Finally, in addition to measuring changes in suspended sediment concentrations, flux, and sources across the experimental flow velocities, we will also quantify the forms of phosphorus associated with fine suspended particles and floc through sequential chemical extractions. Understanding the quality of entrained sediment is necessary to predict its fate at downstream locations of retention.
Modeling will be used to interpret the results of tracer experiments, with the goal to produce a fundamental set of transport parameters representing the role of fine suspended particles, floc, and storage of water and solutes in relatively slow-moving areas of thick vegetation and subsurface pore water.
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