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

飓风哈维的异常降雨事件对德克萨斯州加尔维斯顿湾潮汐入口沉积物的影响

• 批准号: 1763088
• 负责人: William Sager
• 金额: $ 6.46万
• 依托单位: University of Houston
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-11-01 至 2018-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1763088&HistoricalAwards=false
• 关键词: Effects; Hurricane; Harvey; extraordinary; rain

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.

热带气旋导致沿海沉积物和海岸线发生重大变化。虽然人们认识到风暴潮的重要性，但对高降雨事件引起的淡水潮的影响的研究和了解较少。飓风哈维在德克萨斯州-路易斯安那州墨西哥湾沿岸倾倒了约34万亿加仑的雨水，这是美国历史上最多的热带风暴。休斯顿-加尔维斯顿地区正处于降雨的靶心，造成了为期11天的淡水涌入德克萨斯州最大的河口加尔维斯顿湾。由于水流量非常大，外流的水流非常强劲，休斯顿通常水流缓慢的海湾（溪流和河流）的河岸都留下了沿着的泥沙，这表明风暴动员了大量的粗泥沙，其中大部分很可能最终流入了加尔维斯顿湾。就在飓风来袭前几周，休斯顿大学完成了对加尔维斯顿湾两个天然入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水深图和入口底的声学图像，其中显示了沉积物类型、厚度、垂直分层和底部特征等。这项研究重复这些调查，风暴后，并收集沉积物芯记录风暴侵蚀和沉积在玻利瓦尔公路和圣路易斯通行证。风暴前后调查的比较提供了一个前所未有的机会，可以了解飓风哈维的侵蚀和沉积物迁移和沉积。 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全国最繁忙的航运通道之一，而且也是保护加尔维斯顿湾的沿海屏障的大门的拟议位置。两组声纳测量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和适当的政府和规划官员。另一个影响将是培训将参加风暴后海洋地球物理调查的学生。由于休斯顿大学的学生群体多样化，而且是一所为西班牙裔学生服务的大学，因此将努力吸引在科学领域代表性不足的少数民族学生。（侧扫、条带测深和CHIRP），德克萨斯州沿海地区加尔维斯顿湾的两个主要入口，在飓风哈维前几周进行了相同的调查。这次重复调查将记录与飓风哈维有关的前所未有的降雨事件造成的入口和河口的变化，哈维在休斯顿/加尔维斯顿地区倾倒了34万亿加仑的雨水。还将收集河口和入口的沉积物芯。将对岩芯进行重复调查和分析的结果与风暴前进行的调查结果进行比较，以更好地了解沉积物的侵蚀、沉积和再分布情况。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CHIRP声纳（2-16 kHz）对山口附近约50 km轨道线网络上的次底层进行成像，因为该区域的水太浅，无法使用条带声纳。玻利瓦尔公路勘测将使用CHIRP声纳和548千赫侧扫声纳/干涉测深仪，覆盖2x6.5公里的入口段。后一个系统的探测结果将用于制作高分辨率水深测量图，显示风暴侵蚀和沉积造成的深度变化。该声纳还提供了海底的声学后向散射图像，显示地形、沉积物类型、底形和人为碎片。第三次巡航将收集约25个重力核心，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降雨激增的强水流和大量沉积物如何影响入口。这些信息对于完整的海岸沉积模型以及负责海岸管理的机构非常重要，特别是如果计划中的保护加尔维斯顿的海岸屏障横跨玻利瓦尔公路。