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: 2022987
• 负责人: Christopher Hein
• 金额: $ 21.07万
• 依托单位: College of William & Mary Virginia Institute of Marine Science
• 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=2022987&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.

盐沼代表陆地和海洋之间的界面，是一个极其重要的生态系统，可以保护大陆免受风暴影响，同时提供多种有价值的服务，包括鱼类和贝类的繁殖地、过滤陆地废物以及向陆地输出营养物质和食物来源。沿海海洋。然而，由于海平面上升加速和沉积物供应减少，平台沼泽现在面临危险，这可能导致它们被淹死。该项目将研究大风暴如何通过转移沿海地区的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。这种沉积物层（一英寸或更多）有助于沼泽垂直堆积，为沼泽提供养分，并提高盐沼草的生产力。这项研究将了解风暴如何产生这些沉积物，以及近岸和沼泽系统的特征如何影响洪水的方向以及由此产生的悬浮沉积物的分布和沉积。作为一项更广泛的影响活动，研究人员将设计并推动一门关于风暴与海岸线相互作用的研究生课程，涵盖与风暴影响相关的流体动力学、沉积物动力学、地貌学、生态学、人文地理学和经济学等方面。其他更广泛的影响包括：1) 培养与当地利益相关者（包括佐治亚沿海生态系统长期生态研究站点）的新的和现有的关系，以促进数据交换、培养合作和传播研究结果，2) 维护一个提供动机详细信息的项目网站、进展、研究生课程，并提供数据产品的链接； 3）培养博士后1名、博士1名。学生，以及至少两名本科生和两名高中实习生； 4) 通过开发将在弗吉尼亚海洋科学研究所实施的 K-12 实践学习活动，直接向公众进行推广。该研究利用了在佐治亚州萨佩洛岛后面收集的一套沉积岩芯和沼泽表面样本。 2017 年 12 月，量化与飓风艾尔玛相关的沉积物来源（由 NSF 地貌和土地利用动力学计划的 RAPID 拨款支持）。艾尔玛事件后的数据将得到来自近岸、后障壁（河道、湾底、潮滩、沼泽边缘侵蚀）和河流环境中潜在沉积物来源的额外样本的补充。这些来源对风暴沉积物的相对沉积物贡献将通过沉积学（例如颗粒大小、烧失量、有孔虫含量）和地球化学（生物标志物成分、大块沉积物和生物标志物稳定）的新颖组合来确定。和放射性同位素成分）通过主成分分析和非度量多维标度统计进行分析的代理。将使用多维统计工具分析风暴潮海拔、当地水流模式、沉积物厚度和沉积物来源之间的关系。然后，这些数据将与 Delft3D 模型结合使用，该模型可以模拟艾尔玛和其他风暴条件下的流体动力学、沉积物输送以及由此产生的沉积模式，以：1) 探索一系列后障壁子环境中风暴沉积物的来源，2 ) 确定近岸、后屏障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平台的过程、路径和机制（例如，风暴潮水平和持续时间、波浪暴露、当地地貌和河流沉积物排放），以及 4) 评估风暴沉积相对于长期垂直沼泽增生的重要性。该奖项反映了 NSF 的法定使命，并被视为值得通过使用基金会的智力优点和更广泛的影响审查标准进行评估来支持。