Wave- and Wind-Driven Flows Near the Beach

海滩附近的波浪和风驱动的水流

基本信息

批准号：
2044850
负责人：
Britt Raubenheimer
金额：
$ 90.67万
依托单位：
Woods Hole Oceanographic Institution
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2021
资助国家：
美国
起止时间：
2021-03-15 至 2025-02-28
项目状态：
未结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=2044850&HistoricalAwards=false
关键词：
Wave Wind Driven Flows Near

项目摘要

Currents flowing along the shore transport sediments and pollution, place stress on the bottom and affect total water levels, flooding, beach erosion, and subsequent recovery. Yet few observations of these important alongshore flows exist in the inner-surf and swash zones, especially during storms, and the physics driving them during existing observations is undetermined. Along with wave-forcing and alongshore water-level gradients, evidence suggests wind-forcing also may be a significant driver of very shallow-water alongshore currents. Understanding of the physics driving shallow-water flows is needed for nearshore hydrodynamical, morphological and shoreline evolution, and wave overtopping models. This project will leverage funded efforts during the DUNEX study in Duck, NC in fall 2021 with additional moored instrumentation and remote (drone) sensing of the very-near shore to enable evaluation of the wave and wind processes driving alongshore flows near the beach. The project will provide an important new dataset to the community, train a post-doctoral scholar, and contribute to societal interests through informing management of nearshore zones subject to storm-forced erosion and inundation. This project will obtain in situ and remotely sensed field observations for a range of wave conditions to estimate the terms in the momentum balance governing the nearshore zone. Hypotheses to be evaluated are, 1) the forcing of alongshore flows near the beach is cross-shore (depth) dependent; 2) opposing water-level-gradient and oblique-wave forcing drive alongshore flows that change direction between the surf and swash zones, and; 3) oblique-wave and wind forcing dominate inner-surf and swash flows during storms. The DUNEX-funded fieldwork (USCRP, USGS, NSF, USACE, and DoD), which this project builds upon, includes an alongshore array of surfzone ADVs, a single cross-shore transect from the dune to the inner surf with pressure gages, ADVs, and lidar, and frequent bathymetry surveys at the U.S. Army Corps Field Research Facility (USACE-FRF) in fall 2021. FRF also maintains a directional wave array at 8-m, a tide gauge, several anemometers, and a lidar that collects beach and dune topography hourly. The expanded observations proposed here include two cross-shore transects of pressure gages. Additionally, surface flows can be estimated by tracking breaking-wave-generated foam in sequences of images. Drone-based particle image velocimetry and the Optical Current Meter have been used in the past in surfzone conditions. This project will extend and hone these techniques for the swash zone. Observations during storms and moderate wave conditions will be compared and contrasted to examine how processes differ as wave and wind conditions change. The results could significantly improve the ability to predict flows near the beach, the corresponding storm-induced changes to coastal morphology, and the subsequent recovery.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.

沿着海岸流动的水流输送沉积物和污染物，对底部施加压力，并影响总水位、洪水、海滩侵蚀和随后的恢复。然而，在内海浪和冲刷区，对这些重要的沿岸流的观测很少，特别是在风暴期间，并且在现有观测期间驱动它们的物理原理尚未确定。有证据表明，除了波浪力和沿岸水位梯度之外，风力也可能是极浅水沿岸流的重要驱动因素。近岸水动力、形态和海岸线演化以及波浪漫溢模型需要了解驱动浅水流的物理原理。该项目将利用 2021 年秋季在北卡罗来纳州达克进行的 DUNEX 研究期间资助的工作，配备额外的系泊仪器和对非常近海岸的远程（无人机）传感，以评估驱动海滩附近沿岸流动的波浪和风过程。该项目将为社区提供重要的新数据集，培训一名博士后学者，并通过为受风暴侵蚀和洪水影响的近岸地区的管理提供信息，为社会利益做出贡献。该项目将获得一系列波浪条件的现场和遥感现场观测，以估计控制近岸区域的动量平衡项。要评估的假设是，1）海滩附近的沿岸流的强迫与跨岸（深度）相关； 2）相反的水位梯度和斜波强迫驱动沿岸流，在海浪区和冲刷区之间改变方向； 3) 斜波和风力在风暴期间主导内浪和冲流。该项目以 DUNEX 资助的实地工作（USCRP、USGS、NSF、USACE 和 DoD）为基础，包括沿岸的冲浪区 ADV 阵列、从沙丘到内海浪的单个跨岸横断面（带有压力计、ADV）、激光雷达，以及 2021 年秋季在美国陆军军团实地研究设施 (USACE-FRF) 进行的频繁测深调查。FRF 还维护着 8 米的定向波阵列、潮汐计、几个风速计以及每小时收集海滩和沙丘地形的激光雷达。这里提出的扩展观测包括压力计的两个跨岸横断面。此外，可以通过跟踪图像序列中碎波产生的泡沫来估计表面流量。基于无人机的粒子图像测速仪和光电流计过去曾在海浪条件下使用过。该项目将扩展和磨练这些针对斜流区的技术。将比较风暴和中等波浪条件下的观测结果，以研究随着波浪和风力条件变化过程的不同。这些结果可以显着提高预测海滩附近的水流、相应的风暴引起的海岸形态变化以及随后的恢复的能力。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力优势和评估进行评估，被认为值得支持。更广泛的影响审查标准。