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

热带气旋使海岸沉积物和海岸线发生重大变化。虽然人们已经认识到风暴潮很重要，但对高降雨量事件造成的淡水风暴潮的影响研究和了解较少。飓风哈维在德克萨斯州-路易斯安那州墨西哥湾海岸倾倒了约34万亿加仑的雨水，是美国历史上最多的热带风暴。休斯顿-加尔维斯顿地区处于降雨的靶心，导致德克萨斯州最大的河口加尔维斯顿海湾出现了长达11天的非同寻常的淡水涌入。水量如此之大，外流如此之强，以至于在休斯敦通常缓慢流动的海湾(溪流和河流)的两岸都留下了沙子沉积，这表明风暴调动了大量粗沙，其中大部分很可能最终进入加尔维斯顿湾。就在飓风前几周，休斯顿大学完成了对加尔维斯顿湾两个天然入海口的地球物理声纳调查：玻利瓦尔公路和圣路易斯山口。这些调查收集了地球物理数据，从而制作了高分辨率的进水口底板深度图和声学图像，其中显示了沉积物类型、厚度、垂直分层和海底特征等。这项研究重复了风暴后的调查，并收集了沉积物岩心，以记录玻利瓦尔公路和圣路易斯山口的风暴侵蚀和沉积。对风暴前和风暴后的调查进行比较，提供了一个前所未有的机会，让我们了解飓风哈维这种规模的风暴的侵蚀、泥沙输送和沉积情况。该项目的更广泛影响包括将与公众和相关政府机构共享的数据和报告，以帮助管理和决策，因为玻利瓦尔公路不仅是该国最繁忙的航运通道之一，而且也是为保护加尔维斯顿湾而提议的海岸屏障大门的拟议位置。两套声纳测量的比较所得的资料，对规划和管理任何拟议的洪水/风暴潮结构十分重要，研究结果将向公众以及适当的政府和规划官员公布。另一个影响将是对参加风暴后海洋地球物理调查的学生进行培训。由于休斯顿大学有一个多元化的学生群体，是一所为拉美裔服务的机构，将努力吸引在科学中代表性不足的少数族裔的学生。这项研究重复了在玻利瓦路和圣路易斯山口进行的海洋地球物理测量(侧面扫描、条带测深和啁啾)，这是德克萨斯州沿海加尔维斯顿湾的两个主要入海口，在哈维飓风前几周进行了相同的测量。这次重复调查将记录与飓风哈维相关的史无前例的降雨事件对入海口和河口造成的变化，飓风给休斯顿/加尔维斯顿地区带来了34万亿加仑的降雨。还将收集河口和入海口的沉积物岩心。对岩心的重复调查和分析的结果将与风暴前的调查结果进行比较，以更好地了解沉积物的侵蚀、沉积和再分布。它还将研究河口/入海口海底形态的变化。圣路易斯山口调查将使用线性调频声纳(2-16 kHz)在山口附近约50公里的轨道线网络上对底层进行成像，因为该区域的水太浅，无法使用带状声纳。玻利瓦尔公路勘测将使用线性调频声纳和548 kHz侧扫声纳/干涉测深仪器覆盖进水口2x6.5公里的路段。来自后一个系统的探测数据将被用来制作高分辨率的水深地图，该地图将显示风暴侵蚀和沉积造成的深度变化。该声纳还提供了水下的声学后向散射图像，显示了地形、沉积物类型、床面形态和人为碎片。第三次巡航将收集~25个重力核心，这些核心将用于声纳图像的地面实况和寻找风暴事件层。风暴前和风暴后的调查比较，将显示强流和暴雨带来的泥沙负荷如何影响这些进水口。这一信息对于完整的海岸沉积模型以及负责海岸管理的机构都很重要，特别是如果为保护加尔维斯顿而计划修建的海岸屏障是横跨玻利瓦尔公路的话。

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.