Collaborative Research: Coasts in Motion: Quantifying the patterns of coastal change using LIDAR

合作研究：运动中的海岸：使用激光雷达量化海岸变化模式

• 批准号: 0444792
• 负责人: Brad Murray
• 金额: $ 10.71万
• 依托单位: Duke University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-05-01 至 2009-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0444792&HistoricalAwards=false
• 关键词: Collaborative; Research; Coasts; Motion; Quantifying

ABSTRACTThe proposed research involves collecting and analyzing new observations of shoreline change. Four new LIDAR surveys of the North Carolina Outer Banks coastline, each separated by sixmonths, would be conducted. These surveys, combined with previous surveys of the same coastline segments in 1997, 1998, 1999, and 2000, would allow the analysis of patterns of shoreline change over 18 time intervals, ranging in length from six months to eight years. Analysis techniques previously applied to the changes over a single annual interval (Tebbens et al, 2002) quantify statistics including: 1) the amount of shoreline change as a function of alongshore length scale; 2) the distribution of the alongshore-lengths of contiguous zones of erosion and accretion; and 3) the distribution of the magnitudes of erosion and accretion occurring during a time interval. In the previous analysis, the statistics of the patterns of shoreline varied among the different coastline segments measured. These shoreline segments have different orientations, and therefore different effective wave climates. Repeating the analyses over many time intervals will test whether the statistics and the variations from one coastline segment to another are robust. The proposed work would also test a hypothesis and potential model for the main cause of the observed shoreline behaviors. The way the statistics describing the patterns of shoreline change vary as a function of regional wave climate suggests the hypothesis that these changes are driven chiefly by subtle gradients in alongshore transport associated with subtle deviations from a smooth shoreline. Recent work has shown that when waves approach shore from deep water at relative angles greater than approximately 45, shoreline perturbations grow, causing alongshore-heterogeneous shoreline changes on any scale at which perturbations exist (Ashton et al., 2001). Waves approaching from deep-water angles closer to shore-normal tend to smooth out the shoreline. The patterns of change over some extended time period will result at least partly from the interactions between the roughening and smoothing influences, which will depend on the regional wave climate, including the relative proportions of high and low wave-approach angles. A model treating alongshore transport (Ashton et al., 2001; Ashton et al., 2003a; Ashton et al., 2003b) predicts the observed trend with shoreline orientation (regional wave climate) in one of the statistics in the previous analysis (Tebbens et al, 2002). Broader Objectives. If the new data collection and analysis bears out the preliminary findings concerning different coastline segments, and if other model predictions are consistent with the observational results, the model be able to generalize the usefulness of the observations and analyses; the model will provide a way of extending, to any coastline for which a wave climate can be estimated, probabilistic forecasts including expected maximum magnitudes of erosion and accretion over a time interval, and alongshore extents of erosion and accretion zones. Along with the practical benefits such predictions could offer coastal managers, successful model tests would represent an advance in basic understanding of the processes that are important for shoreline changes on scales ranging from hundreds of meters to tens of kilometers. Models that will be able to elucidate the range of coastline changes to be expected in the next century as sea level rise accelerates rely on such improvements in basic understanding. In addition, undergraduate as well as graduate students would participate in the research and the presentation of the results.

建议的研究包括收集和分析海岸线变化的新观测数据。将对北卡罗来纳州外滩海岸线进行四次新的激光雷达调查，每次调查间隔六个月。这些调查与1997年、1998年、1999年和2000年对相同海岸线区段的以往调查相结合，可以分析18个时间间隔内的海岸线变化模式，时间跨度从六个月到八年不等。以前应用于单个年度间隔变化的分析技术(Tebbens等人，2002年)对统计数据进行了量化，包括：1)作为近岸长度尺度的函数的海岸线变化量；2)连续侵蚀和淤积带的沿岸长度分布；以及3)在一段时间间隔内发生的侵蚀和淤积强度的分布。在以前的分析中，不同测量的海岸线段的海岸线模式的统计数字各不相同。这些海岸线段具有不同的方向，因此具有不同的有效波浪气候。在许多时间间隔内重复分析将测试统计数据和从一条海岸线段到另一条海岸线段的变化是否稳健。这项拟议的工作还将检验一种假说和潜在的模型，以确定所观察到的海岸线行为的主要原因。描述海岸线变化模式的统计数据作为区域波浪气候的函数变化的方式表明，这些变化主要是由与平滑海岸线的细微偏离有关的沿岸输送的细微梯度驱动的。最近的工作表明，当海浪以大于约45度的相对角度从深水接近海岸时，海岸线扰动增加，导致存在扰动的任何尺度的近岸非均匀海岸线变化(Ashton等人，2001年)。海浪从更靠近海岸的深水角逼近--这是正常的--往往会平整海岸线。在一段较长时间内的变化模式至少部分是由粗糙和平滑影响之间的相互作用造成的，这将取决于区域波浪气候，包括高和低波浪接近角的相对比例。一个处理沿岸运输的模型(Ashton等人，2001年；Ashton等人，2003a；Ashton等人，2003b)在先前分析中的一个统计数据(Tebbens等人，2002年)中预测了海岸线方向(区域波浪气候)的观测趋势。更广泛的目标。如果新的数据收集和分析证实了关于不同海岸线段的初步结论，并且如果其他模型预测与观测结果一致，该模型将能够推广观测和分析的有用之处；该模型将提供一种方法，将概率预报推广到任何可以估计波浪气候的海岸线，包括在一段时间间隔内预期的最大侵蚀和淤积量以及沿岸侵蚀和淤积区的范围。除了这种预测可能给沿海管理人员带来的实际好处外，成功的模型试验将代表着对过程的基本理解的进步，这些过程对于从数百米到几十公里的尺度上的海岸线变化非常重要。随着海平面上升速度的加快，模型将能够阐明下个世纪预期的海岸线变化范围，这些模型依赖于对基本认识的这种改进。此外，本科生和研究生将参与研究和成果展示。