SGER: Hurricane Katrina Storm Surge Deposition on Deltaic Wetlands

一笔小额的探索性拨款被提议用于收集卡特里娜飓风和丽塔飓风在湿地上沉积的沉积物。飓风在湿地中留下的沉积物数量已经在沿海的几个离散地点被记录下来，但没有对这种沉积进行海岸范围的测量，也没有对沉积后的稳定性进行研究。该海岸沉积物岩心的古年代学表明，飓风发生时无机浓度的峰值是重合的。据保守估计，飓风风暴潮造成的年净沉积物累积量比以前无堤坝的密西西比河堤岸洪水造成的沉积物累积量高出30倍，比旨在恢复湿地的两条河流改道（每条改道耗资1亿美元）中的任何一条都高出200倍。这是一个及时的机会，可以系统地量化强风暴带来的数量，并为有效地恢复这片高度退化的海岸所必需的科学基础设施做出贡献。野外取样的一般目的是：1)估计这些飓风给湿地环境带来的沉积物体积，2)收集足够的材料（用其他资助工具）表征其含量和随后进入土壤或再动员的运动；3)辨别泥沙沉积与植物组成和湿地地貌之间的关系（如果有的话）。样本将使用直升飞机收集最多4天，每天约6小时（天气允许）。数据收集将包括现场照片、沉积物深度测量、各种沉积物收集，以及代表性植物和蜗牛、螃蟹等容易获得的无脊椎动物的存档材料。样品收集量将足以进行粒度分析，土壤和植物中的CNS稳定同位素，以及常规土壤和植物分析（例如盐度，有机百分比，C/N比，微量金属，交换阳离子等）。(2)更广泛意义的非技术解释一笔小额探索性资助被提议用于收集卡特里娜飓风和丽塔飓风沉积在湿地上的沉积物。潮水通过圣伯纳河口向内陆移动，进入新奥尔良地区，在流域的城市化部分留下了大量沉积物，在其他地方留下了数量不详的沉积物。这些沉积物可能是湿地稳定性的重要因素，因为它们的体积或附着在它们上面的营养物质。飓风在湿地中留下的沉积物数量已经在沿海的几个离散地点被记录下来，但没有对整个海岸的沉积物数量进行测量，也没有对它们的稳定性进行沉积后的研究。在视觉识别层之前，快速响应样品收集是必要的，这要困难得多，如果不是不可能的话。这次提议的样本收集的主要目的是量化这些飓风引入这些湿地的沉积物数量，了解沉积速率如何在整个景观中变化，并估计它们对湿地稳定性的重要性。存档的样品必须使用其他资助工具进行分析。对这一海岸沉积物岩心的年代分析表明，飓风发生时无机浓度的峰值是重合的。对这些数据的初步分析，并使用保守的参数值，表明飓风风暴潮带来的沉积物的年净积累量，远远高于以前无堤防的密西西比河的堤岸洪水，也高于为了恢复这片严重退化的海岸而修建的两条改道（每条改道耗资1亿美元）中的任何一条。为湿地带来沉积物和养分的现有恢复方法既不是微不足道的，也不是同质化的努力；它们是规模、成本效益比、可预测性和后果的异质混合体。因此，这项拟议的工作对管理有重大影响。这些结果将立即应用于恢复策略的评估，目前的重点是密西西比河沉积物的大规模转移，理论上是“沉积物剥夺”和“营养紧张”的湿地。这种样品收集和随后的分析的额外好处包括能够追踪沉积物结合的营养物质进入植物的运动，为校准沉积物运输模型和湿地的碳封存提供数据，并建立永久性地块来跟踪土壤演变。

(1) Technical description A small exploratory grant is proposed to collect sediments deposited on wetlands by Hurricanes Katrina and Rita. The amount of sediments that hurricanes leave in wetlands has been documented at a few discrete locations along this coast, but there are no coast wide measurements of this deposition, and no post-deposition studies of their stability. The paleo-chronology of sediment cores from this coast demonstrates the coincidence of peaks in inorganic concentration when hurricanes occur. A conservative estimate is that the net annual accumulation of sediments from a hurricane storm surge is 30X higher than once arrived from overbank flooding of the formerly levee-free Mississippi River, and 200 times greater than from either of the two river diversions meant to restore wetlands (built @$100 million each). This is a timely opportunity to quantify the amounts delivered by strong storms in a systematic way and to contribute to the science infrastructure necessary to efficiently and effectively restore this highly degraded coast. The general purpose of the field sampling is to: 1) estimate the sediment volume brought to wetland environment by these hurricanes, 2) collect sufficient material to characterize (with other funding instruments) its content and subsequent movement into soils or re-mobilization; and, 3) discern relationships, if any, between sediment deposition and both plant composition and wetland geomorphology. Samples will be collected using a helicopter for up to 4 days, for approximately 6 hours daily (weather permitting). Data collection will consist of site photographs, measurements of sediment depth, various sediment collections, and archiving material of representative plants and easily accessible invertebrates such as snails and crabs. The sample collection volume will be sufficient to conduct analyses of particle size, CNS stable isotopes in soils and plants, and routine soil and plant analyses (e.g., salinity, % organic, C/N ratios, trace metals, exchangeable cations, etc. (2) non-technical explanation of the broader significanceA small exploratory grant is proposed to collect sediments deposited on wetlands by Hurricanes Katrina and Rita. The tidal surges moving inland through the St. Bernard estuary and into the New Orleans area left significant amounts of sediments in the urbanized portion of the watershed, and unknown amounts elsewhere. These sediments may be of significant factor in wetland stability because of either their volume or the nutrients attached to them. The amount of sediments that hurricanes leave in wetlands has been documented at a few discrete locations along this coast, but there are no coast wide measurements of this deposition amount, or post-deposition studies of their stability. A rapid response sample collection is necessary before visual identification of the layer is much more difficult, if not impossible. The main purposes of this proposed sample collection are to quantify the amount of sediments introduced to these wetlands by these hurricanes, to understand how the deposition rate varies across the landscape, and to estimate their importance to wetland stability. The archived samples must be analyzed using other funding instruments.An analysis of dated sediment cores from this coast demonstrates the coincidence of peaks in inorganic concentration when hurricanes occur. A preliminary analysis of these data, and using conservative parameter values, suggests that the net annual accumulation of sediments from a hurricane storm surge is much higher than once arrived from overbank flooding of the formerly levee-free Mississippi River or from either of the two river diversions (built @$100 million each) meant to restore this severely degraded coast. The available restoration approaches bringing sediments and nutrients to wetlands are neither trivial nor homogenous endeavors; they are a heterogeneous mixture of size, cost : benefit ratios, predictability and consequences. There are, therefore, significant management implications of this proposed work. These results will have an immediate application to the evaluation of restoration strategies, which are currently focused on the large scale diversions of sediments in the Mississippi River to theoretically 'sediment deprived' and 'nutrient stressed' wetlands. Additional benefits of this sample collection and subsequent analyses include being able to trace the movement of sediment-bound nutrients into plants, to offer data to calibrate sediment transport models and carbon sequestration in wetlands, and to establish permanent plots to follow soil evolution.