Collaborative Research: Physics of Dune Erosion during Extreme Wave and Storm-Surge Events

合作研究：极端波浪和风暴潮事件期间沙丘侵蚀的物理学

• 批准号: 1756449
• 负责人: Daniel Cox
• 金额: $ 30.96万
• 依托单位: Oregon State University
• 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: 2018-09-01 至 2022-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1756449&HistoricalAwards=false
• 关键词: Collaborative; Research; Physics; Dune; Erosion

Sand dunes are often the primary and sometimes only 'line of defense' for coastal infrastructure, and are increasingly constructed and actively managed to protect against extreme events. Coastal managers require knowledge of how dunes will respond under these events so assets can be pre-positioned. Both natural and constructed dunes dissipate energy by modifying breaking waves and runup to limit overwash, thereby minimizing coastal flooding during extreme waves and storm-surge events. However, because extreme physical forces only interact with the dune for a relatively short, yet critical time when the water level rises, there is limited understanding on how dune sediments and vegetation can modify hydrodynamic forces and alter beach-dune profile evolution. This research focuses on dune response to a range of water level and forcing conditions that mimic the passage of an extreme storm event. A near prototype-scale laboratory experiment will be conducted over a mobile bed in the large wave flume at Oregon State University. Physical model studies will occur over a bare dune, a rapidly constructed (loosely compacted) dune following wave-induced erosion, and a dune with live vegetation. Data related to processes ranging from short-term (turbulence) to longer time scales (individual events) will be collected and analyzed to develop a fundamental understanding of the fluid-sediment-vegetation dynamics affecting dune stability, as well as damage mitigation strategies for extreme events. The collected data will be used to validate numerical models. A multiphase flow model sedwaveFoam (created in the open-source OpenFOAM framework), capable of simulating the full profiles of sediment transport under realistic waves, will be extended for dune erosion with or without vegetation. Detailed simulations will further inform the creation of improved parameterizations of turbulence- and wave-scale processes in the event-scale morphodynamic model XBeach. A fragility framework, consistent with risk-based decision support tools, will be created to predict the probability of damage states (e.g., dune volume loss) for a given level and duration of hydrodynamic forcing. The collected data and extensive XBeach simulations will provide required input parameters for the fragility analysis. The data and modeling for different dune archetypes will be used to: (i) identify the fundamental processes (including waves, turbulence, and sediment transport) that drive dune evolution during extreme events; (ii) define the conditions by which dune vulnerability increases as function of berm erosion; (iii) investigate the interaction between the different processes and identify the threshold forcing conditions and time scales beyond which vegetation no longer enhances dune resilience; and (iv) examine the extent a fragility modeling framework can be used to improve risk-based decision for dune erosion during extreme surge and wave events. Natural resource managers and practicing engineers with on-the-ground experience, from Federal and State (Delaware, Texas) levels will contribute to this project through a stakeholder workshop planned for year 3. The fragility framework will be developed in collaboration with managers from Delaware and Texas, allowing prediction of dune damage based on commonly used measures of storm intensity. The project will support PhD and undergraduate students.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.

沙丘通常是沿海基础设施的主要主要，有时只是“防御线”，并且越来越多地结构并积极地设法防止极端事件。沿海经理需要了解沙丘在这些事件下如何做出反应，以便可以预先定位资产。自然和建造的沙丘都通过修改断断续续的波浪和奔跑以限制夸张，从而最大程度地减少在极端海浪和暴风雨事件中的沿海洪水，从而消散了能量。但是，由于极端的物理力仅在水位上升时相对较短但至关重要的时间与沙丘相互作用，因此对沙丘沉积物和植被如何改变流体动力并改变海滩底轮的演变的了解有限。这项研究的重点是对一系列水位的沙丘反应和迫使模仿极端风暴事件的条件。将在俄勒冈州立大学的大波浪水槽中的一张移动床上进行近乎原型规模的实验室实验。物理模型研究将在裸露的沙丘上进行，波浪引起的侵蚀后快速构建（松散压实）沙丘，以及带有活植被的沙丘。将收集和分析与从短期（湍流）到更长的时间尺度（单个事件）的过程相关的数据，以对影响沙丘稳定性的流体 - 补习植被动态发展，以及对极端事件的损害缓解策略。收集的数据将用于验证数值模型。多相流模型Sedwavefoam（在开源式炸药框架中创建），能够在逼真的波浪下模拟沉积物传输的完整曲线，以延伸以延伸，以进行或没有植被的情况。详细的模拟将进一步告知在事件规模的形态动力学模型XBEACH中改善湍流和波尺度过程的参数化。将创建与基于风险的决策支持工具一致的脆弱框架，以预测给定水平的损害状态（例如，沙丘体积损失）的可能性和流体动力强迫的持续时间。收集的数据和广泛的XBEACH模拟将为脆弱性分析提供所需的输入参数。不同的沙丘原型的数据和建模将用于：（i）确定在极端事件中驱动沙丘演化的基本过程（包括波浪，湍流和沉积物传输）； （ii）定义沙丘脆弱性随着护理侵蚀的功能而增加的条件； （iii）研究不同过程之间的相互作用，并确定阈值强迫条件和时间尺度，超出了植被不再增强沙丘的韧性； （iv）检查脆弱性建模框架可用于改善在极端激增和波浪事件中基于风险的沙丘侵蚀的决策。来自联邦和州（德克萨斯州特拉华州）级别的自然资源经理和实践工程师将通过计划第3年的利益相关者研讨会为该项目做出贡献。脆弱框架将与特拉华州和德克萨斯州的经理合作开发，从而可以基于常见的风暴强度措施来预测Dune的损害。该项目将支持博士学位和本科生。该奖项反映了NSF的法定任务，并被认为是值得通过基金会的知识分子优点和更广泛影响的评论标准来评估值得支持的。

项目成果

Evaluating XBeach performance for extreme offshore-directed sediment transport events on a dissipative beach

• DOI: 10.1080/21664250.2021.1976452
• 发表时间: 2021-09
• 期刊: Coastal Engineering Journal
• 影响因子: 2.4
• 作者: Takayuki Suzuki;D. Cox