Collaborative Research: Hurricane Sedimentation on Salt Marshes: Extent, Provenance, and Processes

合作研究：盐沼上的飓风沉积：范围、来源和过程

• 批准号: 2022982
• 负责人: Ioannis Georgiou
• 金额: $ 10.9万
• 依托单位: The Water Institute of the Gulf
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-07-01 至 2024-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2022982&HistoricalAwards=false
• 关键词: Collaborative; Research; Hurricane; Sedimentation; Salt

Salt marshes represent the interface between land and sea and are a vitally important ecosystem that protects the mainland from storms while providing a multitude of valuable services including nursery grounds for fish and shellfish, filtering land-derived wastes, and exporting nutrients and food sources to the coastal ocean. However, platform marshes are now endangered due to accelerating sea-level rise and diminished sediment supplies, which together may lead to their drowning. This project will study how major storms help the sustainability of marshes by transferring sediment from the coastal zone and depositing it in a widespread layer on top of the marsh. This sediment layer (an inch or more) helps the marsh to accrete vertically, fertilizes the marsh with nutrients, and enhances the productivity of the salt marsh grasses. This research will produce an understanding of how storms source these sediments and how characteristics of the nearshore and marsh system influence the direction of floodwaters and the resulting distribution and deposition of the suspended sediment. As a broader impacts activity, the investigators will design and facilitate a graduate-level course on the Interaction of Storms with the Coastline, covering aspects of hydrodynamics, sediment dynamics, geomorphology, ecology, human geography, and economics as they relate to storm impacts. Additional broader impacts include: 1) fostering new and existing relationships with local stakeholders (including the Georgia Coastal Ecosystems Long Term Ecological Research site) to facilitate data exchange, cultivate collaboration, and disseminate findings, 2) maintaining a project website presenting details of the motivation, progress, the graduate course, and providing links to data products; 3) training one postdoctoral researcher, one Ph.D. student, and at least two undergraduate students and two high school interns; and 4) direct outreach to the public through development of hands-on K-12 learning activities to be implemented at the Virginia Institute of Marine Science.The study leverages a suite of sediment cores and marsh surface samples collected behind Sapelo Island, Georgia, in December 2017 to quantify the provenance of sediment deposits associated with Hurricane Irma (supported by a RAPID grant from the NSF Geomorphology and Land-use Dynamics Program). Post-Irma data will be supplemented with additional samples from potential sediment sources within nearshore, backbarrier (channel; bay floor; tidal flat; marsh-edge erosion), and fluvial environments. The relative sediment contributions from each of these sources to the storm deposit will be determined using a novel combination of sedimentologic (e.g., grain size, loss-on- ignition, foraminifera content) and geochemical (biomarker compositions, bulk-sediment and biomarker stable- and radio- isotopic compositions) proxies analyzed through principal component analysis and non- metric multi-dimensional scaling statistics. Relationships among storm-surge elevation, local flow patterns, deposit thickness, and sediment provenance will be analyzed using multi-dimensional statistical tools. These data will then be used in conjunction with a Delft3D model, which can simulate hydrodynamics, sediment transport, and resulting sedimentation patterns during Irma and other storm conditions, to: 1) explore the source of storm deposits across a range of backbarrier subenvironments, 2) determine the relative importance of nearshore, backbarrier, and fluvial reservoirs in providing sediment to saltmarshes during major storms, 3) quantify the processes, pathways, and mechanisms of sediment distribution to the marsh platform (e.g., storm-surge level and duration, wave exposure, local geomorphology, and river sediment discharge), and 4) evaluate the importance of storm sedimentation relative to long-term vertical marsh accretion.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

盐沼是陆地和海洋之间的界面，是一个至关重要的生态系统，保护大陆免受风暴的影响，同时提供多种有价值的服务，包括鱼类和贝类的育苗场，过滤陆地产生的废物，以及向沿海海洋输出营养物质和食物来源。然而，由于海平面加速上升和沉积物供应减少，平台沼泽现在正面临危险，这些因素加在一起可能导致它们被淹没。该项目将研究大风暴如何通过从沿海地区转移沉积物并将其沉积在沼泽顶部的广泛层中来帮助沼泽的可持续性。这层沉积物（一英寸或更多）有助于沼泽垂直生长，为沼泽提供养分，提高盐沼草的生产力。这项研究将产生的风暴源这些沉积物和近岸和沼泽系统的特性如何影响洪水的方向和悬浮沉积物的分布和沉积的理解。作为一个更广泛的影响活动，调查人员将设计和促进一个研究生水平的课程，风暴与风暴线的相互作用，涵盖流体动力学，沉积物动力学，地貌学，生态学，人文地理学和经济学方面，因为它们涉及到风暴的影响。其他更广泛的影响包括：1）促进与当地利益攸关方的新的和现有的关系（包括格鲁吉亚沿海生态系统长期生态研究网站），以促进数据交换，培养合作，传播成果，2）维护一个项目网站，介绍动机，进展，研究生课程的细节，并提供数据产品的链接;（3）培养博士后研究员1名，博士研究生1名。学生，至少两名本科生和两名高中实习生;以及4）通过在弗吉尼亚海洋科学研究所实施的实践K-12学习活动的发展直接与公众联系。该研究利用了在格鲁吉亚萨佩洛岛后面收集的一套沉积物岩心和沼泽表面样本，2017年12月，量化与飓风伊尔玛相关的沉积物沉积物的来源（由NSF地貌和土地利用动力学计划的RAPID资助支持）。后伊尔玛数据将补充额外的样本，从潜在的沉积物来源在近岸，backbarrier（通道;湾底;潮滩;沼泽边缘侵蚀），和河流环境。这些来源中的每一个对风暴存款的相对沉积贡献将使用沉积学的新组合（例如，粒度、烧失量、有孔虫含量）和地球化学（生物标志物组成、整体沉积物和生物标志物稳定同位素和放射性同位素组成）代用指标，通过主成分分析和非度量多维标度统计进行分析。将使用多维统计工具分析风暴潮高程、当地水流模式、存款厚度和沉积物来源之间的关系。然后，这些数据将与Delft 3D模型结合使用，该模型可以模拟Irma和其他风暴条件下的水动力学，沉积物运输和由此产生的沉积模式，以：1）探索一系列障壁后亚环境中风暴沉积物的来源，2）确定近岸、障壁后和河流水库在大风暴期间向盐沼提供沉积物的相对重要性，3）量化沉积物分布到沼泽台地的过程、途径和机制（例如，该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。