RAPID: Collaborative Research: Tracking the Flood Pulse of a Record Discharge of the Brazos River in the Gulf of Mexico

RAPID：合作研究：追踪墨西哥湾布拉索斯河创纪录流量的洪水脉冲

• 批准号: 1829221
• 负责人: Timothy Dellapenna
• 金额: $ 4.5万
• 依托单位: Texas A&M University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-03-01 至 2019-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1829221&HistoricalAwards=false
• 关键词: RAPID; Collaborative; Research; Tracking; Flood

The transport and fate of sediment carried by rivers to the coastal ocean is of great ecological and societal importance. River input is the primary source of land-derived sediment to the marine environment. These particles have significant impacts on the health of coastal ecosystems and the geology and bathymetry of coastal oceans and shipping channels. They directly and indirectly affect fisheries and navigation. This research focuses on the movement of sediments carried into the Gulf of Mexico, via the Brazos River, during the unprecedented rainfall and flooding event that occurred during Hurricane Harvey. The Brazos River ranks as the second largest contributor of nutrients and organic matter to the Gulf of Mexico, after the Mississippi River. Unlike the Mississippi, however, most sediment delivered to the Gulf of Mexico from the Brazos is carried during flooding events like that which accompanied Hurricane Harvey. Little is known about the fate of this sediment. It is not clear if it is retained in the coastal zone, where the nutrients and chemicals it carries affect the coastal environment, or is carried offshore and deposited in the deep waters of the Gulf of Mexico. Through intensive sampling of sediments just offshore the mouth of the Brazos River and further offshore in the Gulf of Mexico in what is known as the Texas Mud Blanket, this project will determine the principal repository of sediments delivered to the western Gulf of Mexico by a major Texas river. The overall goal of this research is to investigate the hypothesis that flood-borne sediment from the Brazos River is initially deposited in the coastal zone and subsequently mobilized and carried offshore with a large fraction of it being deposited in the Texas Mud Blanket. The work builds on the analysis of sea-bottom sediment samples collected in 2017 during flooding associated with Hurricane Harvey. This new program will include two sampling cruises to augment already collected data. The first cruise will entail acquisition of ~25 cores that will indicate sediment deposition and transport in the near-shore region near the Brazos River mouth. Preliminary work indicates that much of the initial deposition of Brazos River sediment occurred east of the original sampling region. The second cruise in will collect additional Brazos region cores and expand sampling into the Texas Mud Blanket, with the goal of documenting changes in Brazos sediment deposition from the Hurricane Harvey flooding. During both cruises, complementary hydrography data will be collected. This includes water column velocities and suspended sediment loads. Provenance of individual layers, within the sediment samples and box cores, will be determined by digital photos and x-radiographs of intact core slabs that show sediment fabric and structures. To differentiate Gulf of Mexico from Brazos River sediments, sub-samples of collected cores will be geochemically analyzed and profiled for short-lived-radioisotope geochronology, water content, grainsize distribution, and mercury and carbonate content. These indicators will help identify the origin of the sediments deposited in the system.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

河流携带的沉积物向沿海海洋的迁移和归宿具有重大的生态和社会意义。河流输入是陆源沉积物进入海洋环境的主要来源。这些微粒对沿海生态系统的健康以及沿海海洋和航道的地质和水深测量有重大影响。它们直接和间接地影响渔业和航运。这项研究的重点是在哈维飓风期间发生的前所未有的降雨和洪水事件期间，通过布拉索斯河进入墨西哥湾的沉积物的运动。布拉索斯河是继密西西比河之后为墨西哥湾输送营养物质和有机物的第二大河流。 然而，与密西西比河不同的是，从布拉索斯河输送到墨西哥湾的大部分沉积物都是在洪水期间携带的，比如飓风哈维。 人们对这些沉积物的命运知之甚少。 目前尚不清楚它是被保留在沿海地区，它携带的营养物质和化学物质影响沿海环境，还是被带到近海并沉积在墨西哥湾的深水沃茨。通过对布拉索斯河口近海和墨西哥湾近海被称为德克萨斯州泥毯的沉积物进行密集取样，该项目将确定德克萨斯州一条主要河流输送到墨西哥湾西部的主要沉积物储存库。 本研究的总体目标是调查的假设，即洪水携带的沉积物从巴西河最初沉积在沿海地区，随后动员和离岸进行的大部分沉积在得克萨斯州泥毯。 这项工作建立在对2017年与飓风哈维相关的洪水期间收集的海底沉积物样本的分析基础上。 这一新方案将包括两次抽样航行，以补充已经收集的数据。第一次航行将需要采集约25个岩心，这些岩心将表明布拉索斯河口附近近岸区域的沉积物沉积和迁移情况。 初步工作表明，布拉索斯河沉积物的最初沉积大部分发生在原始采样区以东。 第二次巡航将收集更多的巴西地区岩心，并将采样扩大到德克萨斯州泥毯，目的是记录飓风哈维洪水造成的巴西沉积物沉积变化。 在这两次航行中，将收集补充的水文数据。这包括水柱速度和悬浮泥沙负荷。沉积物样品和箱式岩芯中各层的来源将通过显示沉积物组构和结构的完整岩芯片的数码照片和X射线照片来确定。 为了区分墨西哥湾和布拉索斯河沉积物，将对收集到的岩芯子样本进行地球化学分析，并分析短寿命放射性同位素地质年代学、含水量、粒度分布以及汞和碳酸盐含量。 该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。