RAPID: Examining Seafloor Dynamics offshore Bogue Banks, North Carolina, Related to Hurricane Florence

美国东部和海湾沿岸沿着的许多社区正在遭受中度至严重的侵蚀。 由北卡罗来纳州海岸管理部门确定的十年海岸线侵蚀率表明，北卡罗来纳州海岸线的侵蚀率不到65%。 慢性长期侵蚀和风暴的间歇性影响鼓励该州大多数沿海社区利用当地离岸海岸沙源进行海滩修复。 一个令人关切的问题是，目前对近海沙洲（补充沿海沙丘和海滩的潜在借砂区）如何应对风暴条件和疏浚活动的了解有限。 2018年9月，飓风佛罗伦萨严重影响了北卡罗来纳州南部和北方南卡罗来纳州，造成海岸侵蚀和洪水。因此，由于这些影响，预计将作出重大的侵蚀减缓努力。 该项目将收集近海沙浅滩的海底测量数据，可用于评估飓风驱动的变化。这项工作的更广泛影响包括学生培训和沿海土地管理者和政策制定者可以使用的信息。飓风佛罗伦萨于2018年9月14日上午在北卡罗来纳州威尔明顿附近登陆，但就在登陆之前，风暴是一场强大的2级飓风，低于前几天的4级飓风。 大范围地区都遭遇了飓风强度的大风，并在东海岸中部沿着产生了显著的风暴潮和巨浪。 水下和水下地貌变化可能是由于强烈的波浪和潮汐活动引起的沉积物运动造成的。 这项研究是对收集海底测绘数据（即，多波束测深法）在北卡罗来纳州的威尔明顿附近的先前勘测区域的一部分上，该区域被称为莫尔黑德市海洋疏浚物处置场。工作将包括收集和解释海底下（CHIRP地震）剖面，还将收集表层沉积物样品并分析粒度，以确定碎屑大小和泥沙运移参数。 这些数据将告知与飓风佛罗伦萨相关的大陆架沉积物输运的性质，并为解释强风暴事件期间的沉积物输运和再分布提供必要的地面实况。 调查和取样将沿着沿着内大陆架进行，在北卡罗来纳州海岸16公里以内，水深一般不到20米。这是一个区域，经常位于近海的沙子借用地点，用于海滩的营养。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。

Many communities along the East and Gulf Coasts of the United States are experiencing moderate to severe erosion. Decadal shoreline erosion rates determined by the North Carolina Division of Coastal Management indicate that less than 65 percent of the North Carolina shoreline is eroding. Chronic long-term erosion and episodic impacts from storms have encouraged most coastal communities in this state to conduct beach nourishments using local off shore sand sources. One concern is present limited knowledge of how offshore sand shoals (potential borrow areas for replenishment of coastal dunes and beaches) are evolving in response to storm conditions and dredging activity. In September, 2018, Hurricane Florence severely impacted southern North Carolina and northern South Carolina, causing coastal erosion and flooding. As a result, significant erosion mitigation efforts are anticipated due to these impacts. This project will collect seafloor measurements from an offshore sand shoal which can be used to evaluate hurricane-driven changes. Broader impacts of the work include student training and information that can be used by coastal land managers and policy makers.Hurricane Florence made landfall as a Category 1 storm near Wilmington, North Carolina on the morning of September 14, 2018 but, just prior to making landfall, the storm was a powerful Category 2 hurricane, down from Category 4 status days prior. Hurricane-force winds were experienced over a large region, and these yielded significant storm surges as well as powerful waves along the central East Coast. Subaerial and subaqueous geomorphic changes likely resulted due to sediment movement resulting from forceful wave and tidal activity. This research is a rapid response to collect seafloor mapping data (i.e., multibeam bathymetry) over a portion of a previously surveyed area near Wilmington, North Carolina, known as the Morehead City Ocean Dredged Material Disposal Site. Work will involve the collection and interpretation of sub-bottom (CHIRP seismic) profiles, Samples of surface sediments will also be collected and analyzed for grain-size to determine clast size and sand transport parameters. These data will inform the nature of shelf sediment transport associated with Hurricane Florence and provide essential ground-truthing for interpretations of sediment transport and redistribution during a strong storm event. Surveys and sampling will take place along the inner continental shelf, within 16 kilometers of the North Carolina shore and water depths generally less than 20 meters. This is the region where offshore sand borrow sites used for beach nourishment are often located. It is also a coastal area that has been relatively understudied due to its shallow and energetic nature.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.