SGER: Hurricane Katrina Storm Surge Deposition on Deltaic Wetlands

(1)建议提供一笔小额勘探拨款，以收集卡特里娜和丽塔飓风在湿地上沉积的沉积物。飓风在湿地留下的沉淀物的数量已经在这一海岸的几个离散位置得到了记录，但没有整个海岸对这种沉淀物的测量，也没有对其稳定性的沉积后研究。该海岸沉积物岩心的古年代学表明，当飓风发生时，无机浓度的峰值重合。一项保守的估计是，飓风风暴潮带来的泥沙年净积累量是此前没有堤防的密西西比河泛滥时的30倍，是两条旨在恢复湿地的河流改道中的200倍(每条改道耗资1亿美元)。这是一个及时的机会，可以有系统地量化强风暴造成的影响，并为有效和有效地恢复这一高度退化的海岸所需的科学基础设施作出贡献。实地采样的一般目的是：1)估计这些飓风给湿地环境带来的沉淀量，2)收集足够的材料，以确定其含量和随后进入土壤的移动或再动员的特征，以及，3)辨别沉积物沉积与植物组成和湿地地貌之间的关系。样本将使用直升机进行最多4天的采集，每天大约6个小时(如果天气允许)。数据收集将包括现场照片、沉积物深度的测量、各种沉积物收集，以及代表性植物和容易接触到的无脊椎动物(如蜗牛和螃蟹)的档案材料。样本采集量将足以进行土壤和植物中的颗粒大小、CNS稳定同位素分析，以及常规土壤和植物分析(例如盐度、有机百分比、碳/氮比、痕量金属、可交换阳离子等)。(2)对更广泛意义的非技术性解释建议提供一小笔探索性赠款，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。潮汐通过圣伯纳德河口向内陆移动，进入新奥尔良地区，在分水岭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。飓风在湿地留下的沉淀量已经在这一海岸的几个离散位置得到了记录，但没有整个海岸测量这个沉淀量，也没有沉积后对其稳定性的研究。在目测层的识别变得更加困难之前，快速反应样品收集是必要的，如果不是不可能的话。这项拟议的样本采集的主要目的是量化这些飓风给这些湿地带来的沉淀量，了解沉积速率在整个景观中的变化，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。对这一海岸的沉积物岩心进行的年代分析表明，飓风发生时无机浓度的峰值是一致的。对这些数据的初步分析，并使用保守的参数值表明，飓风风暴潮带来的泥沙年净积累量，远高于以前没有堤防的密西西比河泛滥，或两条河流改道中的任何一条(每条改道造价1亿美元)，这两条改道的目的是恢复这片严重退化的海岸。现有的将沉积物和营养物质带到湿地的修复方法既不是微不足道的，也不是同质化的；它们是规模、成本：效益比、可预测性和后果的不同组合。因此，这项拟议工作具有重大的管理影响。这些结果将立即应用于恢复战略的评估，目前这些战略的重点是密西西比河沉积物大规模转向理论上的“沉积物匮乏”和“营养紧张”湿地。这种样品采集和后续分析的其他好处包括能够追踪沉积物结合的营养物质进入植物的移动，提供数据以校准湿地中的沉积物传输模型和碳固存，以及建立跟踪土壤演变的永久地块。

(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.