RAPID: Collaborative Research: Sediment and Contaminant Mobilization by Extreme Flooding associated with Hurricane Florence

High magnitude riverine floods are an increasingly recognized process shaping landscapes, mobilizing sediment and contaminants and building stratigraphic records. Tropical cyclones are the dominant mechanism that delivers extreme precipitation and produces high magnitude riverine flooding. Hurricane Florence made landfall in North Carolina on Sep 14, 2018 where it stalled and generated heavy precipitation and historic flooding on rivers across the lower Atlantic coastal plain. These floods reshaped floodplains and mobilized a range of contaminants from industries in the region, providing a unique opportunity to study the geomorphic and environmental effects of an extreme flood. The PIs will systematically collect sediment deposited by the flood in the lower reaches of the Pee Dee River system, one of the largest watersheds in the southeastern US, to investigate the lateral and longitudinal patterns of sediment and associated contaminant deposition immediately following flooding caused by a landfalling hurricane. This research will clarify how extreme flood events carry sediments and contaminants from land to sea, a process affecting the health of people and ecosystems along the way. Identifying and quantifying contaminant inputs to Winyah Bay has critical implications for coastal ecosystem management and public health. Findings will be communicated to local stakeholders and decision makers. The project will fund a multidisciplinary team that encompasses geoscientists, environmental scientists, and environmental engineers across a range of career stages. A diverse group of undergraduate and graduate students from Coastal Carolina University and Northeastern University will participate in the proposed activities to gain research experience and develop research activities that can be built into their academic programs.

Landfalling hurricanes generating riverine flooding hazards on the Atlantic Coastal Plain affect millions of area residents. This project takes advantage of a rare extreme flood to observe how this type of event shapes the floodplain of an alluvial river system and transports sediment and contaminants from land and point sources to the coastal ocean. The PIs will collect floodwater sediment samples before other processes remove or erode the flood-born deposits. They will analyze sediment characteristics, conduct 7Be dating of sediment to confirm timing of deposition, and measure concentrations of organic (Polycyclic aromatic hydrocarbons; PAHs) and trace metal (V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Ag, Cd, Sn, Hg, Pb, and Bi) contaminants in the floodwater sediments. Like flood and contaminant research resulting from Hurricane Harvey (2017), the work is highly relevant and illustrative of the need to track contaminant dispersal as a public health issue. Using both PAHs and the selected trace metals will provide stronger source identification for PAH compounds, e.g., run-off from roads, parking lot sealcoat, or associated with coal combustion. The proposed activities build on an active NSF project (EAR-1804799) supporting PIs Munoz and Shen that develops sedimentary records of flooding on alluvial rivers (paleofloods) by providing a modern analogue of sediment deposition by an extreme flood. Data will aid in understanding landscape and ecosystem responses to extreme flooding and improve paleoflood and paleo-tempestological reconstructions of past storm activity and periodicity in heavily populated coastal regions.

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.