RAPID - Plume Dynamics under Increased Sediment Discharge following Floods

RAPID - 洪水后泥沙排放增加下的羽流动力学

• 批准号: 1603957
• 负责人: Alexander Yankovsky
• 金额: $ 7.01万
• 依托单位: University of South Carolina at Columbia
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-11-15 至 2017-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1603957&HistoricalAwards=false
• 关键词: RAPID; Plume; Dynamics; under; Increased

South Carolina suffered from record rainfalls on 2-4 October 2015 resulting in massive erosion and flooding, dam breaching and overtopping of lakes and ponds. The floodwaters spread in the coastal ocean as a buoyant plume. The objective of this RAPID study is to examine the plume dynamics under increased sediment discharge but otherwise close to normal oceanic conditions on the shelf. Repeated shipboard surveys of salinity, temperature, sediment concentration and flow velocity will be conducted within the freshwater plume originating from Winyah Bay, SC, where the Pee Dee River and the Waccamaw River discharge. The surveys will be repeated over the course of a few weeks as the sediment discharge subsides. These floods will affect coastal sediment budget, beach and inner shelf morphology, and should be accounted for by coastal developers, managers and other stakeholders. The observed flood was extremely "flashy" and the resulting freshwater pulse carried an increased concentration of pollutants due to multiple failures of sewage treatment plants and other leaks. Better understanding of the freshwater discharge dispersal and mixing in the coastal ocean will help to mitigate similar events in the future and ultimately to better protect a fragile coastal ecosystem. This project will provide the required field research experience for several undergraduate students from the USC Marine Science Program.This event is an opportunity to investigate a new element to the dynamics of freshwater discharge-driven coastal buoyant plumes: density variations associated with deposition of heavy sediment load prior to the dispersal and mixing of the low saline water. These density variations might have important consequences for the plume dynamics: enhancement of currents further offshore, formation of secondary bulges and the eddy-driven offshore mass and tracer fluxes. Record-breaking flashy rainfalls in SC in early October in combination with light to moderate wind forcing conditions on the coast allow the study to capture two regimes of the sediment-laden discharge adjustment: (i) rapid mixing of the discharge due to its initial lack of buoyancy, and (ii) "re-energizing" of the plume once sediments are deposited and the discharge regains its buoyancy.

南卡罗来纳州在2015年10月2日至4日遭受了创纪录的降雨，导致巨大的侵蚀和洪水，大坝的侵蚀和湖泊的超越。洪水以浮羽流在沿海海洋中。这项快速研究的目的是检查沉积物排放增加的羽流动力学，但在架子上接近正常的海洋条件。重复的盐度，温度，沉积物浓度和流速的船上调查将在源自南卡罗来纳州Winyah湾的淡水羽流中进行，在那里，小便迪河和Waccamaw河的放电。随着沉积物放电的消退，将在几周的时间内重复调查。这些洪水将影响沿海沉积物预算，海滩和内货架形态，应由沿海开发商，经理和其他利益相关者考虑。观察到的洪水非常“浮华”，由于污水处理厂的多次失败和其他泄漏，导致的淡水脉搏造成了增加污染物的浓度。更好地了解淡水排放的分散和沿海海洋混合将有助于减轻将来的类似事件，并最终更好地保护脆弱的沿海生态系统。该项目将为来自USC海洋科学计划的几位本科生提供所需的现场研究经验。这项事件是一个机会，可以调查新元素，以了解淡水排放驱动的沿海浮力羽毛：与沉积物沉积相关的密度变化在分散和混合低盐水水之前加载。这些密度变化可能会对羽流动力学产生重要的后果：进一步的近海电流增强，次级凸起的形成以及涡流驱动的海上质量和示踪剂通量。 10月初，SC的创纪录的闪烁降雨与沿海的轻度到中等的风力强迫条件相结合，使研究捕获了两个充满沉积物的排放调整的策略：（i）由于其最初缺乏，因此迅速混合了排放量浮力，（ii）一旦沉积沉积物并恢复其浮力后，羽流的“重新启动”。