Collaborative Research: CROSSTEX - An Experimental Study of Onshore Bar Movement

合作研究：CROSSTEX - 陆上酒吧运动的实验研究

• 批准号: 0351297
• 负责人: James Kirby
• 金额: $ 25.32万
• 依托单位: University of Delaware
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-06-01 至 2009-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0351297&HistoricalAwards=false
• 关键词: Collaborative; Research; CROSSTEX; Experimental; Study

ABSTRACTOCE-0351297Cross-shore sediment transport processes play a crucial role in the annual episodic cycles of erosion and accretion on most beaches. Great strides have been made in our understanding of erosional processes during intense storm events, and models have shown reasonable skill in predicting storm bar formation and offshore migration. A parallel understanding of accretional processes, particularly the landward migration of bars, has not yet been obtained. Consequently, predictive models of cross-shore transport processes exhibit little skill in predicting morphology change for any extended sequence of erosional and accretional events. Part of the lack of present understanding stems from a paucity of available data sets. In the field, measurement of profile evolution during an accretional event requires having both a detailed surveying program and sufficient hydrodynamic instrumentation in place at the right time in order to allow testing of process based models. The Duck '94 experiment has provided one such data set. However, cross-shore processes in the field can be masked or altered by the lateral diffusion of the large longshore transport volume, and can be further complicated by the evolution of two dimensional bathymetric variations, leading to longshore variability of the cross-shore transport pattern. Large scale laboratory experiments have been conducted at near-to-field scale, eliminating most of the concerns over scaling issues and providing an isolated look at purely cross-shore processes. However, the existing data sets do not provide a long enough look at the shoreward movement of bars during accretional events, and do not provide measurements of the multiple events that are needed to provide both calibration and a blind test of predictive models. The PI's will conduct an extended cross-shore morphology experiment to examine the shoreward migration of shore-parallel sand bars under accretional wave conditions. The experiments will be conducted in the large wave flume facility at Oregon State University. The experimental program will primarily examine the relative roles of suspended load versus bedload modes of transport. Also included will be whether "plug-flow" (mass failure of the upper layer of the sand bed) plays a significant role during shoreward bar movement events. Extensive use will be made of hydrodynamic models (based on Boussinesq or nonlinear mild-slope formulations) to design experimental conditions and assist in choice of instrument placement. The acquired data set will be used to test the predictions of both the hydrodynamic models and the sediment transport models, which are driven for extended periods by the hydrodynamic models. This data set which will adequately describe the hydrodynamics and sediment transportmechanisms associated with a significant period of shoreward bar movement, will provide a test base for evaluating modern sediment transport models which is presently lacking. The improvement of process-based predictive models which could result from access to such a data base could markedly increase the coastal engineering and nearshore oceanography communities' ability to predict the seasonal variability of shoreline erosion and accretion in the U.S.'s heavily populated coastal zones. The results of this project will be disseminated broadly through publications in peer-reviewed journals, presentations at international and national conferences, workshops for scientists interested in the data set and for industry members and coastal managers, inclusion of the results in classroom material, and participation by undergraduate students.

Abstractoce-0351297 Cross-Shore沉积物运输过程在大多数海滩上的年度侵蚀和增生周期中起着至关重要的作用。在激烈的暴风雨事件中，我们对侵蚀过程的理解取得了长足的进步，模型在预测风暴棒形成和近海迁移方面表现出了合理的技能。尚未获得对吸收过程的平行理解，尤其是酒吧的地向迁移。因此，跨近岸运输过程的预测模型在预测任何扩展的侵蚀和吸收事件序列的形态变化方面几乎没有技巧。缺乏当前理解的一部分是由于缺乏可用的数据集。在该领域，在积聚事件中测量轮廓演化需要在适当的时间进行详细的测量程序和足够的流体动力仪器，以便允许测试基于过程的模型。 Duck '94实验提供了一个这样的数据集。然而，通过较大的长岸运输量的横向扩散可以掩盖或改变田间的跨岸过程，并且可以通过二维测深的变化的演化进一步复杂化，从而导致跨岸运输模式的长岸变异性。大规模实验室实验是在近对场上进行的，消除了大多数对缩放问题的担忧，并提供了纯粹的跨岸过程的孤立观察。但是，现有的数据集并未足够长时间观察到积聚事件期间条形的shoreward运动，也没有提供对提供校准和对预测模型的盲目测试所需的多个事件的测量。 PI将进行延伸的跨近岸形态实验，以检查在吸收波条件下沿岸平行砂条的沿岸迁移。实验将在俄勒冈州立大学的大波浪水槽设施中进行。实验计划将主要检查悬浮载荷与床载荷模式的相对作用。还包括“插头”（沙床上层的质量故障）是否在Shoreward Bar运动事件中起着重要作用。大量使用将由流体动力学模型（基于Boussinesq或非线性温和斜坡配方）来设计实验条件并有助于选择仪器的位置。获取的数据集将用于测试流体动力模型和沉积物传输模型的预测，这些模型是由流体动力学模型长期驱动的。这个数据集将充分描述与岸杆运动相关时期的流体动力和沉积物传输机制，将为评估目前缺乏的现代沉积物传输模型提供测试基础。通过访问此类数据库可能导致的基于过程的预测模型的改进可以显着提高沿海工程和近海海洋学社区预测美国人口稠密的沿海地区海岸线侵蚀和积聚的季节性变异性的能力。该项目的结果将通过同行评审期刊的出版物，国际和民族会议的演讲，对数据集有兴趣的科学家以及行业成员和沿海经理感兴趣的科学家的讲习班，将结果包括在课堂材料中，以及本科生的参与。