Alongshore Variable Dune Erosion During Extreme Storms

极端风暴期间沿岸沙丘的变化

• 批准号: 1829136
• 负责人: Britt Raubenheimer
• 金额: $ 76.6万
• 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: 2018
• 资助国家: 美国
• 起止时间: 2018-08-15 至 2023-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1829136&HistoricalAwards=false
• 关键词: Alongshore; Variable; Dune; Erosion; During

Despite the importance of dunes, there are few concurrent field observations of surf and swash zone waves and currents, and beach and dune morphology during extreme storms. Thus, model simulations usually are calibrated and evaluated by comparison with observed pre- to post-storm changes in topography. The wave and current processes that drive these topographic changes, and the time and space scales of changes during periods of extreme storm activities, are not well understood. The project examines hydrodynamic processes during extreme storms that result in alongshore variable dune erosion over 100-m scales owing to wave collision. The outcomes of the project will improve coastal management, help protect coastal communities, and sustain coastal resources. The project will provide field training to undergraduates, recent graduates, and young professionals embarking on coastal careers by offering 2- to 3-week-long fieldwork-focused internships. This internship program will provide critical experience to participants enhancing the potential job placement in the field of coastal engineering. In addition, a graduate research student will be trained in the use of numerical models for the simulation of nearshore processes. Unique observations of surf and swash zone waves, and surf, beach, and dune morphology before, during, and after 3 large storms, combined with numerical model simulations, are used to determine the causes of alongshore variability of dune erosion, over 100-m scales. The hypotheses examined are: (i) alongshore variable dune erosion and recession rates depend on the initial surf zone bathymetry and associated hydrodynamics, and (2) positive feedbacks between wave runup, reflection, and offshore transport at the dune toe lead to erosional hotspots during storms. The importance during storms of surf-zone bathymetry and hydrodynamics to dune evolution, and the feedbacks between surf- and swash-zone processes and erosional hotspots are examined. The PIs will investigate how waves propagate across the surf zone and beach during extreme storms, and how parameterizations of wave processes used in numerical models may be different during more moderate conditions. Numerical simulations of dune evolution are sensitive to user-selected parameters, as well as to the offshore and surf-zone bathymetry, which often are not well known. Laboratory observations indicate that given best-fit sediment transport coefficients, models may simulate dune changes reasonably well, despite overestimating water levels and underestimating runup fluctuations. The research undertaken as part of this project will determine if the simulated hydrodynamics are accurate throughout extreme storms, and if the time history of simulated sand-level change is correct.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.

尽管沙丘很重要，但在极端风暴期间，几乎没有同时对冲浪和潮湿的区域波和潮流的野外观察，海滩和沙丘的形态。因此，通常通过比较观察到的地形后变化后变化来校准模型模拟和评估。尚未很好地理解驱动这些地形变化的波浪和当前过程，以及极端风暴活动期间变化的时间和空间尺度。该项目研究了极端风暴中的流体动力学过程，导致由于波浪碰撞而导致100米尺度上的可变沙丘侵蚀。该项目的结果将改善沿海管理，有助于保护沿海社区并维持沿海资源。该项目将通过提供2到3周的以现场工作为重点的实习，为本科生，近期毕业生和年轻专业人士提供现场培训。该实习计划将为参与者提供重要的经验，以增强沿海工程领域的潜在工作安置。此外，研究生研究生将接受用于使用数值模型来模拟近海过程的培训。在3次大风暴中，之中和之后，对冲浪和偏斜的区域波以及冲浪，海滩和沙丘形态的独特观察结果，结合了数值模型模拟，用于确定沙丘侵蚀范围易变性的原因，超过100 m。 所检查的假设是：（i）沿岸可变的沙丘侵蚀和衰退率取决于初始的冲浪区域测深和相关的流体动力学，以及（2）在风暴中，在沙丘上的波动，反射，反射和近海运输之间的阳性反馈导致侵蚀性热点。研究了冲浪区域测深的暴风雨和水动力学对沙丘进化的重要性，并检查了冲浪和偏离区域和侵蚀热点之间的反馈。 PI将在极端风暴期间调查波浪如何在冲浪区和海滩上传播，以及在更中等条件下，数值模型中使用的波过程的参数化可能会有所不同。沙丘演化的数值模拟对用户选择的参数以及海上和冲浪区的测深敏感，这通常不知道。实验室观察表明，尽管高估水位并低估了运行的波动，但模型鉴于最合适的沉积物传输系数，模型可能会很好地模拟沙丘变化。作为该项目的一部分进行的研究将确定模拟的流体动力学是否在整个极端风暴中都准确，如果模拟沙级变化的时间历史是正确的。该奖项反映了NSF的法定任务，并被认为是通过基金会的知识分子优点和更广泛影响的审查标准来评估的。

项目成果

The Roles of Bathymetry and Waves in Rip‐Channel Dynamics

测深和波浪在 Rip 海峡动力学中的作用

• DOI: 10.1029/2023jf007389
• 发表时间: 2024
• 期刊: Journal of Geophysical Research: Earth Surface
• 作者: Christensen, D. F.;Raubenheimer, B.;Elgar, S.
• 通讯作者: Elgar, S.

Coastal topography and hydrogeology control critical groundwater gradients and potential beach surface instability during storm surges

沿海地形和水文地质控制风暴潮期间的关键地下水梯度和潜在的海滩表面不稳定

• DOI: 10.5194/hess-26-5987-2022
• 发表时间: 2022
• 期刊: Hydrology and Earth System Sciences
• 影响因子: 6.3
• 作者: Paldor, Anner;Stark, Nina;Florence, Matthew;Raubenheimer, Britt;Elgar, Steve;Housego, Rachel;Frederiks, Ryan S.;Michael, Holly A.
• 通讯作者: Michael, Holly A.

Modeling the hydrodynamics and morphodynamics of sandbar migration events

• DOI: 10.1016/j.coastaleng.2021.103885
• 发表时间: 2021-03
• 期刊: Coastal Engineering
• 影响因子: 4.4
• 作者: Y. Rafati;T. Hsu;S. Elgar;B. Raubenheimer;E. Quataert;A. V. van Dongeren