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

这项拟议的研究验证了这样一种假设，即沉积物运移动力学在控制地形模式方面发挥了作用，地形模式对佛罗里达大沼泽地的山脊和沼泽景观的生态至关重要。也就是说，在历史水流条件下，假设从开阔水域泥沙到植被覆盖的山脊的泥沙再分配调节了山脊宽度，但随着湿地的排水和分区，再分配的幅度已经减小，允许山脊扩展到开阔水域泥滩并丧失地形非均质性。项目假设将通过野外和实验室试验相结合的方式进行验证，并通过对控制植被环境中絮凝泥沙运移动力学和流动的质量和动量平衡方程的数值模拟来验证。絮体传输力学的实验分析将描述在沉积床中携带不同粒级的临界剪应力和湍流强度，不同剪切参数的水流产生的平衡集料尺寸分布和浓度，集料沉降速度，以及由于植被和微地形而发生在山脊/坡地横断面上的湍流和水流剖面的变化。为此，将在实验室和现场水槽中进行流量监测和一系列使用天然絮凝物的输送实验和示踪剂测试。基金还将资助森林山高中环境科学磁石项目学生实施补充科学博览会项目，重点是使用快速评估光学技术开发横跨山脊/泥沙横断面的有机质混合模型(可用作泥沙输送模型的验证措施)，并阐明环境水质对絮凝有机泥沙输送特性的影响。这项拟议的研究建立在以前研究的基础上，该研究通过建立一个模型来预测泥沙沉积的大小和空间分布作为流速和水位的函数，从而证明了从开阔水域到植被环境中泥沙再分配的存在。在大沼泽地，沉积物主要以有机絮体的形式存在，其机理尚不清楚。同样，尽管絮凝作用在世界范围内河流、湿地和河口的悬浮泥沙动力学中占主导地位，但关于流经植被环境对絮体沉积和迁移的影响以及絮凝动力学对景观形态和演变的预测模型的研究尚不存在。这项研究开发了一套实验室和现场实验，旨在解决模型开发所需的有关絮体传输机制的关键问题，并建立了这些机制如何影响景观演变的原始模型。因此，拟议的研究将为改进对沉积物迁移和景观动态的预测开创先例，这将对河口科学、河流地貌学、湿地科学和污染物迁移产生影响。广泛的影响--该项目的结果将广泛传播给(1)实地研究人员，方法是在一次会议上组织一次关于絮凝剂沉积迁移对景观动态的影响的特别会议，(2)通过在景观小组会议和大沼泽地生态恢复会议上定期出版一篇关于沼泽景观动力学的科普文章，向参与实施综合沼泽恢复计划的决策者，以及(3)通过发表一篇关于沼泽景观动态的科普文章，向公众广泛传播该项目的成果。此外，模型结果将对政策和社会产生影响，因为它将导致对流速和水期的改进建议，这些建议应得到实施，以恢复山脊和塌方景观。购买激光衍射式粒度分析仪带来的基础设施增强将有利于K-12、本科生和研究生水平的课堂演示、实验室和实地研究。研究工作还将加强美国地质调查局、科罗拉多大学和K-12教育之间的合作努力，并将协同补充美国地质调查局关于山脊和沼泽景观中生物地球化学反馈机制和养分运输的现有项目。最后，这项研究通过与佛罗里达州西棕榈滩森林山高中的环境科学磁铁项目建立坚定的合作伙伴关系，并通过为目前的博士生提供研究支持，加强了对未来几代科学家的知识转移。

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.