RAPID: Hurricane-induced Shelf Sediment Transport and Deposition after Hurricane Ida in 2021

飓风艾达是一种破坏性极强的4级风暴，于2021年8月29日登陆路易斯安那州埃尔默岛和卡米纳达角，带来风暴潮和13英尺的海浪，这是自卡特里娜飓风以来未曾见过的。近年来，这些大风暴对大陆架沉积物运输的作用以及这些事件对沿海变化的影响已变得十分重要。随着仪器和技术的改进，开展了更多的实地研究，以测量风暴事件期间近海大陆架上的泥沙输送过程。然而，由于风暴路径的不可预测性以及获取测量的困难和费用，仍然缺乏现场数据。在这个项目中，将在两个挖泥坑中采集样本，这两个挖泥坑用于在风暴后补充海滩，以检验飓风在大陆架上的沉积物重新分配中发挥主要作用并可能在挖泥坑中造成大量沉积物沉积和挖泥坑壁大量浪费的最重要的假设。挖泥坑可能是路易斯安那州这种沙子的可持续资源，但它们作为沉积物捕获器的有效性需要了解它们沿大陆架的长期演变和海洋过程。由于数据收集的目的是捕捉大陆架和两个挖泥坑内的飓风后沉积物，因此数据收集具有时间敏感性。该项目支持对海洋本科生和研究生的培训。虽然人们很容易知道大陆架可能是充满活力的环境，但缺乏关于大飓风期间和之后立即发生的沉积物迁移和沉积的海洋观测数据。特别是，在飓风期间，床沙和悬移质的泥沙通量可以增加一到两个数量级。然而，这些沉积物可能会被随后发生的事件抹去。挖泥坑是飓风后沉积物沉积的极好记录器，可以在大陆架上提供记录这些重大事件的天然捕获盆地。该项目将在飓风后对南佩尔托和沙点疏浚坑以及沿路易斯安那州内陆架10米等深线的飓风伊达以东和以西的多个站点的泥沙输送和地层进行量化。将利用过去七年(2014年至2021年)的历史数据，对飓风前后的情况进行比较。飓风条件经常在沿海环境中造成大规模浪费和海底山体滑坡，这对大陆架上现有的关键基础设施构成危险，如可再生风能和电信基础设施。飓风艾达也可能引发挖泥坑墙坍塌和向外迁移，可能对附近受飓风影响的平台和管道构成重大危险。这一裁决反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Hurricane Ida was a very destructive Category 4 storm that made landfall at Elmer’s Island and Caminada Headlands, Louisiana on 29 August 2021, bringing storm surge and waves of 13 feet, not seen since Hurricane Katrina. The importance of the role of these large storms on shelf sediment transport and the effect of these events on coastal change has become apparent in recent years. With improvements in instrumentation and technology, more field studies have been conducted to measure sediment transport processes on offshore continental shelves during storm events. However, due to the unpredictability of storm paths and the difficulties and expense in obtaining measurements, there is still a lack of field data. During this project, samples will be obtained in two dredge pits, which are used to replenish beaches after these storms, to test the overarching hypothesis that hurricanes play a major role in redistributing sediment on the continental shelf and likely produce massive sediment deposition in dredge pits and extensive mass wasting of the dredge pit walls. Dredge pits may be a sustainable resource for this sand in Louisiana, but their efficacy as sediment traps requires an understanding of their long-term evolution and marine processes along the continental shelf. Data collection is time-sensitive because of the goal of capturing the post-hurricane sediment on the continental shelf and within the two dredge pits. The project supports the training of undergraduate and graduate students at sea.While it is readily known that continental shelves can be energetic environments, there is a lack of marine observational data for sediment transport and deposition that occurs during and immediately after major hurricanes. In particular, the sediment fluxes of bed and suspended loads can increase one to two orders of magnitude during hurricanes. However, these deposits may be obliterated by subsequent events. Dredge pits serve as excellent recorders of post-hurricane sediment deposition and can provide natural capture basins on continental shelves that record these major events. This project will result in a post-hurricane quantification of sediment transport and stratigraphy of the South Pelto and Sandy Point dredge pits as well as multiple stations east and west of Hurricane Ida along the 10-m isobath on the inner Louisiana shelf. A comparison will be made between the pre- and post-hurricane conditions by leveraging historical data over the past seven years (2014 to 2021). Hurricane conditions often cause mass wasting and submarine landslides in coastal environments, which pose a hazard to existing critical infrastructure on the continental shelf, such as renewable wind energy and telecommunication infrastructure. It is also likely that Hurricane Ida triggered dredge pit wall collapse and outward migration, possibly posing a major hazard to hurricane-impacted platforms and pipelines in the vicinity.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.