RAPID: Assessment of coastal & offshore change due to Hurricane Florence: Wrightsville Beach, North Carolina

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Hurricanes that make landfall at low-lying coastal regions, such as barrier-islands like those on the Outer Banks of the US southeast coast, are known to cause significant impacts on the coastline and installed infrastructure within reach of higher and more forceful than normal waves and the tidal surge. Storm impacts can range from minor beach and dune erosion to complete coastal devastation (as seen, for example, with Hurricane Matthew in 2016 and with Hurricane Michael in 2018 that came ashore at Mexico Beach, FL). Abundant scientific research has documented the serious impacts these storms have on beaches and other subaerially exposed parts of the coastline. However, much less is known about the role the offshore region, extending seaward from beaches, plays in coastal response and resilience. This research helps fill this gap by using shipboard marine geophysical surveys and other techniques to map the seabed in coastal waters offshore Wrightsville Beach that lies just east of Wilmington, North Carolina and is near where Hurricane Florence made landfall. Wrightsville Beach is associated with recreational areas and commercial and residential buildings. Goals of the work are to document changes in seabed bathymetry, geomorphology, and sediment distribution resulting from Hurricane Florence out to water depths of ~10 meters. The resulting data will be used to try and determine why effects on beaches, even at locations on the same beach that are closely spaced, can be very different. Broader impacts of the work include student training and providing information to coastal managers, local policy makers, and the public about the link between strong storms, like hurricanes, and beaches and the offshore region. This project seeks to understand what role the offshore region at Wrightsville Beach, North Carolina, which was close to the center of Hurricane Florence's landfall, played in the highly variable beach erosion observed at three locations. A range of shipboard marine survey techniques that include a combination of single-beam bathymetry, side scan sonar, and seabed grab sampling techniques, will be used to characterize the three locations. These new data will be compared to pre-Florence beach elevation data and off shore surveys and will be augmented by Hurricane Florence-induced wind and wave data that are publicly accessible from local offshore buoys. These data will be used to test, validate, and compare with predictions obtained from the SWAN numerical hydrodynamic model developed by the Delft coastal group in The Netherlands. If good correlations can be found between the data/observations and model output, similar methods could be adopted and employed by coastal scientists and managers elsewhere to better assess potential risk areas and mitigation strategies for hurricane strikes at other barrier island locations.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.