CAREER: Swash Zone Sediment Transport

这一职业项目旨在通过实验室和现场工作，使用一种新的推移质层(非常接近静止床平面)中的泥沙运移测量装置，提高对泥沙输移过程的了解和预测能力。冲浪区是靠近海岸线的区域，在那里，由波浪驱动的水流交替地冲上冲下海滩表面，并最终消耗它们的能量。因此，潮汐过程是海岸形态发生变化的基本机制之一(例如，海岸线对海平面变化的反应)。由于大部分人口生活在海岸线附近，全球海平面在过去十年中以每年3毫米的速度上升(IPPC WGII，2007年)，美国近85%的沙质海岸线正在侵蚀(Thornton等人，2000年)，因此有真正的社会需求来更好地了解这些过程。目前的预测模型由于不能准确描述推移质输运的重要性而受到极大的限制。这一限制主要是由于这样一个事实，即不存在对依赖于时间的推移质输运的可靠测量，即使时间综合陷阱数据表明，推移质往往是主要的输运方式(Horn和Mason，1994)。本项目将通过以下步骤完成泥沙输运的量化任务：(1)测试和使用一种新型的推移质传感器以获得难以捉摸的泥沙测量结果；(2)量化推移质和悬沙作为海滩坡度、波浪条件和泥沙相位的函数的相对重要性，以开发新的泥沙输送公式；(3)研究泥沙平流和跨越泥沙/泥沙边界的交换在泥沙输送信号中的作用；以及(4)利用实验室和现场数据可靠地对泥沙输送进行参数化。其结果将是更好地理解推移质输运在重塑海滩面貌中的作用，从而加强对海岸地貌变化的预测，并设计更有效和更经济的缓解程序。广泛影响：这项研究将拓宽对海岸泥沙输送物理的理解，并将显著提高预测海岸现象(如海滩侵蚀和海滩营养性能)的能力。更广泛地说，测量技术和数据集将极大地提高对流体力学领域广泛关注的颗粒边界层过程的科学理解。研究成果将通过综合和持续的外联活动传播给工程师和非专业人员。特拉华大学工程外展办公室、当地学校教师和教育课程专家将合作并协助启动针对高中生和使用16英尺便携式波浪水槽的教师培训研讨会的“教室中的海滩”扩展计划。这项研究将支持一名少数民族本科生暑期实习生与教职员工和研究生并肩进行研究。实习的招聘将在附近的HBCU通过与NSF赞助的LSAMP计划合作进行。

This CAREER project aims to advance understanding and predictive capability of sediment transport processes occurring in the swash zone through laboratory and field efforts using a new measurement device for sediment transport in the bedload layer (very near the at-rest bed level). The swash zone is the area near the shoreline where wave-driven flows alternately wash up and down the beach face and ultimately expend their energy. Thus, swash processes are one of the fundamental mechanisms by which coastal morphological change happens (e.g. shoreline response to changing sea level). With much of the population living near the coastline, global sea levels rising at a rate of 3 mm/yr over the last decade (IPPC WGII, 2007) and nearly 85% of sandy U.S. coastlines eroding (Thornton et al., 2000), there is a real societal demand for better understanding of these proceses. Current predictive models are extremely limited by their inability to accurately characterize the significance of bedload transport. This limitation is primarily due to the fact that no reliable measurements of time-dependent bedload transport exist, even though time-integrated trap data demonstrates that bedload is often the dominant transport mode (Horn and Mason, 1994). This project will approach the difficult task of quantifying swash-zone bedload transport with the following steps:(1) test and use a novel bedload sensor to obtain elusive bedload measurements in the swash zone; (2) quantify the relative importance of bedloadand suspended load as a function of beach slope, wave conditions and swash phase to develop new sediment transport formulations; (3) investigate the role of sediment advection and exchange across thesurf/swash boundary in the swash-zone sediment transport signal; and (4) utilize laboratory and field data to reliably parameterize swash-zone sediment transport. The result will be an improved understanding of the role of bedload transport in reshaping the beach face leading to enhanced predictions of coastal morphologic change and the design of more effective and economical mitigation procedures.Broader Impacts: This study will broaden understanding of the physics of coastal sediment transport and will lead to significant improvement in the ability to predict coastal phenomena such as beach erosion and beach nourishment performance. More generally, the measurement techniques and data sets will greatly improve scientific understanding of particle-laden boundary layer processes that are of broad interest in the area of fluid mechanics. Research results will be disseminated to engineers and lay people through integrated and ongoing outreach activities. The University of Delaware's Engineering Outreach Office, local school teachers and education curriculum experts will collaborate and assist in initiating the "beach in a classroom" outreach program for high school students and teacher training workshops using a 16-foot portable wave flume. The study will support a minority undergraduate summer intern in performing research side-by-side with faculty and graduate students. Recruitment for the internship will be conducted at nearby HBCU's through collaboration with the NSF-sponsored LSAMP Program.