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Analysis of Virginia Barrier Island Shoreline Movement and Correlations to Sea Level and Wave Height Changes and Teleconnection Patterns

机译：弗吉尼亚屏障岛海岸线运动及其与海平面和波高变化及遥相关型的关系分析

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摘要

The Virginia barrier islands stretch from Assateague Island in the north to Fisherman's Island in the south. This string of islands is subject to frequent North Atlantic extra-tropical storm and hurricane influence. In addition, sea level rise has the potential to cause continued shoreline loss and inlet widening for this island group. This dissertation describes the effect of sea level rise, changes in wave height, and teleconnection pattern (AO, NAO, and MEI) correlations to shoreline location changes to the islands and inlet location and width changes. Locations of island shorelines were determined from satellite and aircraft images using ArcGIS software and the USGS Digital Shoreline Analysis System (DSAS). Geographically registered images were digitized, and multiple transect locations on each island were measured from a common offshore baseline using DSAS. The resulting distances along with the remote sensing image dates were used to construct time series of shoreline location for each island. Data frequency was controlled by image availability, and ranged from weekly to semi-monthly. Approximately 250 shorelines per island from 1990 to 2014 were digitized. The results were then interpolated to give a monthly shoreline location for each transect. The combined observations were analyzed by empirical orthogonal function (EOF) and wavelet analysis. The analysis shows that the barrier islands are moving to the south as well as becoming narrower. As a group, the shoreline movement is primarily correlated with sea level change (r2 = 0.41). The islands also respond to storms and other episodic events. The response can be resilient or catastrophic depending on the extent of shoreline loss which precedes the event. If the island shoreline has narrowed to a width that cannot withstand wave and high water level induced loss, the island and associated shoreline is permanently lost. The rate of shoreline loss returns to the pre-storm rate within several weeks after the events unless island shore is permanently lost during the event. Increased losses of island length were concentrated in years 2004-2005 and 2009-2010. Wavelet analysis confirmed and explained the EOF results by showing the presence of shoreline change cycles which become more intense at times of shoreline loss. A large reversal of shoreline loss was caused by the placement of 3.5 million m3 of sand on the south end of Wallops Island in 2012 and the attachment of a large offshore shoal to the north end of the same island. Wreck and Ship Shoal Islands have had a net shoreline gain over the study period but with continued southward migration. There are ten inlets between the Virginia Barrier islands. Five of these had width increases of more than 100% during the study period. Two of the five widened by more than 200%. As the barrier islands have become shorter, the inlets have become wider. Due to the episodic nature of the loss of some islands, the inlet width gains have also been episodic. The statistical correlation of sea level variability with inlet width change has a coefficient of determination (r2) of 0.77. The extent of this correlation is very large and may be due to a combination of sea level effects on both the islands and inlets. Inlet width change between 1999 and 2014 was analyzed by EOF and wavelet analysis. EOF analysis of all inlets indicates in addition to general widening, substantial inlet changes generally occur during high water level and high wave events associated with passing hurricanes and tropical storms. Ocean shoreline and inlet trends are for continued shoreline loss for most islands, island migration southward, and inlet widening. The findings of this study can be directly applied to adaptation or possible island protection measures where warranted.
机译：弗吉尼亚屏障岛从北部的阿萨蒂格岛延伸到南部的渔人岛。这串岛屿经常受到北大西洋热带副热带风暴和飓风的影响。此外，海平面上升有可能导致该岛群持续的海岸线损失和入海口扩大。本文描述了海平面上升，波高变化以及遥相关模式（AO，NAO和MEI）与海岸线位置变化对岛屿的影响以及入口位置和宽度变化的影响。使用ArcGIS软件和USGS数字海岸线分析系统（DSAS）从卫星和飞机图像确定了岛屿海岸线的位置。将地理注册的图像数字化，并使用DSAS从共同的近海基线测量每个岛屿上的多个横断面位置。由此产生的距离以及遥感影像数据被用于构建每个岛屿的海岸线位置的时间序列。数据频率受图像可用性控制，范围从每周到每半个月不等。从1990年到2014年，每个岛屿约有250条海岸线被数字化。然后对结果进行插值，以得出每个样带的每月海岸线位置。通过经验正交函数（EOF）和小波分析对合并的观测值进行分析。分析表明，障碍岛正在向南移动，并且越来越狭窄。作为一个整体，海岸线运动主要与海平面变化相关（r2 = 0.41）。这些岛屿还应对风暴和其他突发事件。根据事件发生前海岸线损失的程度，响应可能是弹性的或灾难性的。如果岛上的海岸线变窄到无法承受海浪和高水位引起的损失的程度，则该岛和相关的海岸线将永久丢失。在事件发生后的几周内，海岸线损失率将恢复到暴风雨发生前的速度，除非在事件发生期间岛上的海岸永久丧失。岛长损失的增加集中在2004-2005年和2009-2010年。小波分析通过显示海岸线变化周期的存在证实并解释了EOF结果，海岸线变化周期在海岸线损失时变得更加强烈。 2012年，瓦洛普斯岛南端放置了350万立方米的沙子，并将大型离岸浅滩连接到该岛的北端，导致海岸线损失大幅度逆转。在研究期间，沉船岛和船舶浅滩群岛的海岸线净增加，但继续向南迁移。弗吉尼亚屏障群岛之间有十个入口。在研究期间，其中五个的宽度增加超过100％。五个中的两个扩大了200％以上。随着隔离岛变短，入口也变宽。由于某些岛的损失是情景性的，因此入口宽度的增加也是情景性的。海平面变化与入口宽度变化的统计相关性具有0.77的确定系数（r2）。这种相互关系的程度非常大，可能是由于海平面对岛屿和入海口的综合影响。通过EOF和小波分析分析了1999年至2014年之间的入口宽度变化。所有进水口的EOF分析表明，除了总体变宽外，在与飓风经过和热带风暴有关的高水位和高浪事件期间，通常还会发生大量进水口变化。海洋海岸线和入海口趋势是大多数岛屿的海岸线持续损失，岛屿向南迁移以及入海口扩大。这项研究的结果可直接用于适应或必要的岛屿保护措施。

著录项

  • 作者

    Haluska, James Daniel.;

  • 作者单位

    Old Dominion University.;

  • 授予单位 Old Dominion University.;
  • 学科 Physical oceanography.
  • 学位 Ph.D.
  • 年度 2017
  • 页码 126 p.
  • 总页数 126
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 古生物学;
  • 关键词

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