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: 0446744
• 负责人: Stephen Burroughs
• 金额: $ 5万
• 依托单位: University of Tampa
• 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=0446744&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.

摘要拟议的研究涉及收集和分析海岸线变化的新观察结果。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，每次间隔六个月。这些调查与之前在 1997 年、1998 年、1999 年和 2000 年对同一海岸线段进行的调查相结合，将能够分析 18 个时间间隔内海岸线变化的模式，时间间隔从六个月到八年不等。以前应用于单一年度间隔变化的分析技术（Tebbens 等，2002）量化统计数据，包括：1）海岸线变化量作为沿岸长度尺度的函数； 2）邻近侵蚀和增生区域的沿岸长度分布； 3）一段时间内发生的侵蚀和增生程度的分布。在前面的分析中，测量的不同海岸线段之间的海岸线模式统计有所不同。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。在多个时间间隔内重复分析将测试从一个海岸线段到另一个海岸线段的统计数据和变化是否稳健。 拟议的工作还将测试观察到的海岸线行为主要原因的假设和潜在模型。描述海岸线变化模式的统计数据随区域波浪气候而变化，这表明了这样的假设：这些变化主要是由与平滑海岸线的微妙偏差相关的沿岸运输的微妙梯度驱动的。最近的研究表明，当波浪以大于约 45 度的相对角度从深水接近海岸时，海岸线扰动就会增加，导致存在扰动的任何规模的沿岸异质海岸线变化（Ashton 等，2001）。从接近海岸法线的深水角度接近的波浪往往会使海岸线变得平滑。一段较长时间内的变化模式至少部分是由粗糙化和平滑化影响之间的相互作用造成的，这将取决于区域波浪气候，包括高波接近角和低波接近角的相对比例。处理沿岸运输的模型（Ashton 等人，2001；Ashton 等人，2003a；Ashton 等人，2003b）预测了先前分析（Tebbens 等人，2002）的一项统计数据中观察到的海岸线方向（区域波浪气候）趋势。 更广泛的目标。如果新的数据收集和分析证实了有关不同海岸线段的初步发现，并且如果其他模型预测与观测结果一致，则该模型能够概括观测和分析的有用性；该模型将提供一种方法，将概率预报扩展到可以估计波浪气候的任何海岸线，包括一段时间内预计的最大侵蚀和增生幅度，以及沿岸侵蚀和增生区域的范围。除了此类预测可以为沿海管理者带来的实际好处之外，成功的模型测试将代表着对对从数百米到数十公里范围内的海岸线变化非常重要的过程的基本理解的进步。随着海平面上升加速，能够阐明下个世纪海岸线预期变化范围的模型依赖于这种基本理解的改进。 此外，本科生和研究生将参与研究和结果展示。