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.

尽管沙丘的重要性，有几个并发的现场观察冲浪和冲带波和电流，和海滩和沙丘形态在极端风暴。因此，通常通过与观测到的风暴前后地形变化进行比较来校准和评估模型模拟。驱动这些地形变化的波浪和水流过程，以及极端风暴活动期间变化的时间和空间尺度，还没有得到很好的理解。该项目研究极端风暴期间的流体动力学过程，这种风暴由于波浪碰撞而造成100米尺度以上的沿岸沙丘侵蚀。该项目的成果将改善沿海管理，帮助保护沿海社区和维持沿海资源。该项目将通过提供为期2至3周的以实地考察为重点的实习，为本科生、应届毕业生和开始沿海职业的年轻专业人士提供实地培训。该实习计划将为参与者提供重要的经验，提高沿海工程领域的潜在就业机会。此外，一名研究生将接受使用数值模型模拟近岸过程的培训。独特的观察冲浪和冲带波，冲浪，海滩，沙丘形态之前，期间和之后3个大风暴，结合数值模型模拟，用于确定沿岸沙丘侵蚀的变化，超过100米的尺度的原因。 检验的假设是：（i）沿岸可变沙丘侵蚀和后退速率取决于初始碎波带水深测量和相关的流体动力学，以及（2）波浪爬高、反射和沙丘趾处的离岸输运之间的正反馈导致风暴期间的侵蚀热点。在风暴的冲浪区水深和水动力沙丘演变的重要性，和冲浪和冲带过程和侵蚀热点之间的反馈进行了检查。PI将研究在极端风暴期间波浪如何传播穿过碎波带和海滩，以及在更温和的条件下，数值模型中使用的波浪过程的参数化如何不同。沙丘演变的数值模拟对用户选择的参数以及对通常不为人所知的近海和冲浪区水深测量很敏感。实验室观测表明，给定最佳的泥沙输运系数，尽管高估了水位，低估了上升波动，但模型可以相当好地模拟沙丘变化。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在整个极端风暴中是否准确，以及模拟的沙水平变化的时间历史是否正确。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

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