RAPID: Collaborative Research: Marsh Sedimentation due to Hurricanes Florence and Michael Flooding Event in SC

RAPID：合作研究：佛罗伦萨飓风和南卡罗来纳州迈克尔洪水事件造成的沼泽沉积

• 批准号: 1904496
• 负责人: Christopher Hein
• 金额: $ 1.22万
• 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: 2018
• 资助国家: 美国
• 起止时间: 2018-12-01 至 2019-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1904496&HistoricalAwards=false
• 关键词: RAPID; Collaborative; Research; Marsh; Sedimentation

Hurricanes are responsible for the destruction of sandy shorelines and devastation to coastal cities and residential communities. However, scientists have recently begun to recognize that they can have net positive influences on some coastal systems. In particular, although storm waves may cause surface excavation and erosion of the marsh edge in coastal wetlands, hurricanes may also cause net sedimentation during storm surge inundation: storm waves and currents stir sediment off the bottom in the nearshore and within bays and deposit this suspended sediment on marshes during the accompanying storm surge. Although this process is infrequent, a single hurricane can add more inorganic sediment to the marsh surface than is emplaced by daily processes acting over several decades. It has also been shown that marsh plant communities benefit from storm sedimentation due to the added nutrients derived from the new mud. Thus, hurricanes can significantly increase the resiliency of marshes and help their sustainability in a regime of accelerating sea-level rise. This past September, Hurricane Florence was predicted to be a category 4 hurricane and wreak havoc along the North Carolina coast. However, upper wind shear significantly reduced wind velocities, downgrading the storm to a category 1 hurricane by the time it made landfall. Still as the hurricane moved inland, precipitation associated with the storm deluged coastal regions of North and South Carolina with 6 to 20 inches of rain. This amount of rain over a three day period greatly increased the stage and discharge of local rivers, several of which empty directly into Winyah Bay in central South Carolina. These flood waters carried large plumes of suspended sediment to the coastal ocean and to the proximal marshes. We plan to measure this river-derived sediment in the Cape Romain region and compare this sedimentation event to storm-surge-derived deposits mapped in 2017 following Hurricane Irma.The major goal of this study is to document the potential benefits of increased rates of inorganic sedimentation caused by Hurricanes Florence and Michael to the marsh system backing the Cape Romain cuspate foreland. Unlike Hurricane Irma in 2017, which generated high-energy waves, strong onshore winds, and a 1 m storm surge, and resulted in the deposition of a 1-2 cm thick mud layer, Hurricanes Florence and Michael had little direct impact on the marshes of central South Carolina due to their weaker winds and less impactful storm tracks. However, Florence, and to a much lesser extent Michael, produced intense precipitation, which vastly increased the stage and discharge of coastal rivers by an order of magnitude. Several of these rivers carried floodwaters and substantial quantities of suspended sediment directly into Winyah Bay and nearby marsh systems. Repeat coring of the Cape Romain marshes at locations previously sampled following Hurricane Irma would provide a rare opportunity to compare a high riverine sedimentation event to that produced by an energetic hurricane. We will revisit and resample our Cape Romain locations (10 stations along two transects), as well as measure our ten long-term SET sites near Muddy Bay (in Cape Romain). In addition, at least four other sites along the transects will be occupied to ensure broad spatial coverage of the hurricane-related deposit. Sediment cores, shallow surface sediment samples, and observations would be taken at each station to document new sedimentation, and determine if we can differentiate sediment delivered by each Hurricane Irma (wave- and storm-surge- induced from ambient sediment) and Hurricane Florence (introduction of new riverine sediment). The latter will be done via observations, sedimentological analyses (grain size, texture, physical structures, color) of short sediment cores and bulk geochemical analyses (TOC, TN, delta13CTOC, delta15NTN) of surface samples associated with each Hurricanes Irma and Hurricanes Florence/Michael. In addition, our existing SET records would be examined to determine if they capture past storm-associated spikes in sedimentation. Funds from NSF support field sampling and the lab processing and geochemical analyses of 20 surface sediment samples (10 each from Irma and Florence/Michael), and short-core analysis from our 10 cores to be collected at new sampling stations.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.

飓风是造成沙质海岸线的破坏以及对沿海城市和住宅社区的破坏。但是，科学家最近开始认识到，他们对某些沿海系统的净积极影响。特别是，尽管暴风雨波可能会导致沿海湿地中沼泽边缘的表面发掘和侵蚀，但飓风在风暴浪潮淹没期间也可能引起净沉降：风暴波和潮流在近岸和海湾内的底部搅动沉积物，并将这种悬浮的沉积物沉积在伴随的风暴浪潮中。尽管这个过程很少发生，但单个飓风可以在沼泽表面增加更多的无机沉积物，而不是几十年来的日常过程所带来的。还显示，由于新泥浆衍生出的养分，沼泽植物群落受益于风暴沉积。因此，飓风可以显着提高沼泽的弹性，并在加速海平面上升的政权中帮助其可持续性。去年9月，预计佛罗伦萨飓风将是北卡罗来纳州海岸的4级飓风，并造成严重破坏。但是，上风剪切大大降低了风速，到登陆时，风暴将风暴降级到1类飓风。当飓风迁移到内陆时，降水与北卡罗来纳州北部和南卡罗来纳州的沿海地区相关，下雨了6至20英寸。在三天的时间里，这次降雨大大增加了当地河流的阶段和排放，其中几条直接排入南卡罗来纳州中部的Winyah湾。这些洪水将大量的悬浮沉积物带到沿海海洋和近端沼泽地。 We plan to measure this river-derived sediment in the Cape Romain region and compare this sedimentation event to storm-surge-derived deposits mapped in 2017 following Hurricane Irma.The major goal of this study is to document the potential benefits of increased rates of inorganic sedimentation caused by Hurricanes Florence and Michael to the marsh system backing the Cape Romain cuspate foreland.与2017年的飓风Irma不同，该飓风产生了高能波，强烈的陆上风和1 m的风暴潮，导致了1-2厘米厚的泥土层的沉积，佛罗伦萨飓风和迈克尔对南卡罗来纳州中部卡罗来纳州沼泽的直接影响很小，因为它们的弱风和影响力的风暴轨迹较小。然而，佛罗伦萨和迈克尔在较小程度上产生了巨大的降水，从而大大增加了沿海河流的阶段和排放的数量级。这些河流中有几条将洪水和大量悬浮的沉积物直接带入Winyah湾和附近的沼泽系统。在飓风Irma之后先前采样的地点，Romain Cape Romain沼泽的重复加油将提供一个难得的机会，将高级河流沉积事件与充满活力的飓风所产生的河流沉积事件进行比较。我们将重新访问并重新采样我们的Cape Romain位置（沿两个横断面的10个站点），并测量我们在Muddy Bay附近的十个长期设置（位于Romain角）。此外，将占领沿横断面的至少四个地点，以确保与飓风相关的沉积物的广泛空间覆盖。沉积物核心，浅层沉积物样品以及每个站点都会进行观察，以记录新的沉积物，并确定我们是否可以区分每种飓风Irma（与环境沉积物）和飓风佛罗伦萨（引入新河流沉积物）所传递的沉积物。后者将通过与每个飓风Irma和rricricanes Florence/Michael相关的表面样本的较短沉积物核心和大量地球化学分析（TOC，TN，Delta13ctoc，delta15ntn）的观测，粒度，质地，物理结构，物理结构，颜色）进行完成。此外，将检查我们现有的集合记录，以确定它们是否捕获了过去与暴风雨相关的峰值。 NSF支持现场抽样的资金以及20个表面沉积物样本（来自IRMA和佛罗伦萨/迈克尔迈克尔的10个）的实验室处理和地球化学分析，以及我们10个核心的短核分析将在新的采样站收集。该奖项反映了NSF的法定任务，并通过评估了基金会的智力效果。