Effects of Hurricane Harvey's extraordinary rain event on sedimentation at the tidal inlets of Galveston Bay, Texas

热带气旋导致沿海沉积物和海岸线发生重大变化。虽然人们都知道风暴潮很重要，但高降雨事件造成的淡水涌动的影响却很少得到充分的研究和理解。飓风哈维在德克萨斯州-路易斯安那州墨西哥湾沿岸倾倒了约 34 万亿加仑的雨水，这是美国历史上热带风暴中最多的一次。休斯敦-加尔维斯顿地区是降雨的中心，导致长达 11 天的淡水涌入德克萨斯州最大的河口加尔维斯顿湾。水流量如此之大，流出的水流如此之强，以至于休斯顿通常缓慢流动的海湾（溪流和河流）沿岸都留下了沙子沉积物，这表明风暴移动了大量的粗沉积物，其中大部分可能最终流入加尔维斯顿湾。就在飓风发生前几周，休斯顿大学完成了对加尔维斯顿湾的两个天然入口：玻利瓦尔路和圣路易斯通道的地球物理声纳调查。这些调查收集了地球物理数据，生成了入口层的高分辨率深度图和声学图像，其中显示了沉积物类型、厚度、垂直分层和底部特征等。这项研究在风暴后重复了这些调查，并收集了沉积物核心，以记录玻利瓦尔路和圣路易斯山口的风暴侵蚀和沉积。风暴前和风暴后调查的比较提供了前所未有的机会，可以了解飓风哈维级别的风暴的侵蚀、沉积物输送和沉积情况。 该项目的更广泛影响包括将与公众和相关政府机构分享的数据和报告，以帮助管理和决策，因为玻利瓦尔路不仅是全国最繁忙的航运通道之一，而且也是拟议保护加尔维斯顿湾的沿海屏障大门的位置。两组声纳调查的比较信息对于规划和管理任何拟议的洪水/风暴潮结构至关重要，研究结果将提供给公众以及适当的政府和规划官员。另一个影响将是对参加风暴后海洋地球物理调查的学生的培训。由于休斯顿大学拥有多元化的学生群体，并且是一所为西班牙裔服务的机构，因此将努力吸引来自科学领域代表性不足的少数族裔的学生。这项研究在玻利瓦尔路和圣路易斯山口重复了海洋地球物理调查（侧扫描、测深线和 CHIRP），玻利瓦尔路和圣路易斯山口是德克萨斯州沿海加尔维斯顿湾的两个主要入口，在飓风“哈维”发生前几周也进行了相同的调查。这项重复调查将记录与飓风哈维相关的史无前例的降雨事件导致的入口和河口的变化，该事件给休斯顿/加尔维斯顿地区带来了 34 万亿加仑的降雨。还将收集河口和入口的沉积物岩心。岩心重复调查和分析的结果将与风暴前的调查结果进行比较，以更好地了解泥沙侵蚀、沉积和重新分布。它还将检查河口/入口海底形态的变化。 圣路易斯山口勘测将使用 CHIRP 声纳 (2-16 kHz) 对山口附近约 50 公里轨道线网络的底层进行成像，因为该区域的水太浅，无法使用条带声纳。 Bolivar Roads 勘测将使用 CHIRP 声纳和 548 kHz 侧扫声纳/干涉测深仪器覆盖入口的 2 x 6.5 公里部分。后一个系统的探测将用于制作高分辨率测深图，该图将显示风暴侵蚀和沉积引起的深度变化。该声纳还提供水底的声学反向散射图像，显示地形、沉积物类型、河床形态和人为碎片。第三次巡航将收集约 25 个重力核心，这些重力核心将用于声纳图像的地面实况并寻找风暴事件层。风暴前和风暴后调查的比较将显示强流和降雨潮的大量泥沙负荷如何影响入口。这些信息对于完整的沿海沉积模型以及负责沿海管理的机构非常重要，特别是如果计划在玻利瓦尔公路上修建保护加尔维斯顿的沿海屏障。

Tropical cyclones cause significant changes in coastal sediments and shorelines. While there is an understanding that storm surges are important, the effects of fresh water surges from high rainfall events are less well studied and understood. Hurricane Harvey dumped ~34 trillion gallons of rainwater on the Texas-Louisiana Gulf of Mexico coast, the most of any tropical storm in U.S. history. The Houston-Galveston area was at the bullseye of the rainfall, creating an extraordinary 11-day fresh water surge into Galveston Bay, the largest Texas estuary. Water flow volumes were so high and outflow currents so strong that sand deposits were left all along the banks of Houston's normally slow-flowing bayous (streams and rivers), indicating that large volumes of coarse sediment were mobilized by the storm, much of which likely ended up in Galveston Bay. Just weeks prior to the hurricane, The University of Houston completed geophysical sonar surveys of the two natural inlets to Galveston Bay: Bolivar Roads and San Luis Pass. These surveys gathered geophysical data that resulted in the production of high-resolution depth maps and acoustic images of the inlet floors which showed sediment types, thickness, and vertical layering and bottom features, among other things. This research repeats those surveys, post-storm, and collects sediment cores to document storm erosion and deposition at Bolivar Roads and San Luis Pass. A comparison of the pre- and post-storm surveys provides an unprecedented opportunity to learn about the erosion and sediment transport and deposition of a storm the magnitude of Hurricane Harvey. Broader impacts of the project include data and reports that will be shared with the public and relevant government agencies to aid in management and decision making because Bolivar Roads is not only one of the busiest shipping channels in the nation but is also the proposed location for the gates of a coastal barrier that has been proposed to protect Galveston Bay. Information from a comparison of the two sets of sonar surveys will be critical for planning and managing any proposed flood/storm surge structure and results of the study will be made available to the public and appropriate government and planning officials. An additional impact will be the training of students who will participate in the post-storm marine geophysical survey. Because the University of Houston has a diverse student body and is a Hispanic-serving institution, efforts will be made to engage students from minorities under-represented in the sciences.This research repeats marine geophysical surveys (side scan, swath bathymetry, and CHIRP) at Bolivar Roads and San Luis Pass, the two major inlets to Galveston Bay in coastal Texas where identical surveys were taken just a few weeks prior to Hurricane Harvey. This repeat survey will document changes to the inlets and estuary resulting from the unprecedented rainfall event associated with Hurricane Harvey, which dumped 34 trillion gallons of rain on the Houston/Galveston area. Sediment cores from the estuary and inlets will also be collected. Results of the repeat survey and analyses of the cores will be compared to the results of the survey taken pre-storm to get a better understanding of sediment erosion and deposition and redistribution. It will also examine changes in estuary/inlet seafloor morphology. The San Luis Pass survey will use a CHIRP sonar (2-16 kHz) to image subbottom layers over a network of ~50 km of track lines near the pass because the water in this area is too shallow for swath sonars. The Bolivar Roads survey will cover a 2 x 6.5 km section of the inlet using the CHIRP sonar and a 548 kHz side-scan sonar/interferometric bathymetry instrument. Soundings from the latter system will be used to make a high-resolution bathymetry map, which will show changes in depth caused by storm erosion and deposition. This sonar also provides acoustic backscatter images of the water bottom, showing topography, sediment type, bedforms, and anthropogenic debris. A third cruise will collect ~25 gravity cores, that will be used for ground-truth of the sonar images and to look for a storm event layer. Comparison of pre- and post-storm surveys will show how the strong currents and heavy sediment loads of the rainfall surge affected the inlets. This information is important for complete coastal sedimentation models as well as for agencies tasked with coastal management, especially if the planned coastal barrier to protect Galveston is built across Bolivar Roads.