RAPID - Impacts of Hurricane Florence on Coastal and Inner Shelf Environments: Onslow Bay, North Carolina

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Hurricane Florence was an immense 2018 September storm that caused significant coastal erosion in North Carolina on the Outer Banks. Rainfall events associated with the storm caused unprecendented flooding in coastal and inland locations that impacted sediment delivery to the coastal ocean. In addition, the hurricane generated a storm surge of 2 to 3 meters. Elevated water levels combined with the tremendous and sustained wave energy caused substantial erosion to coastal islands and inlets and likely impacted sediments and the morphology of the seafloor across the continental shelf. This research project collects time-critical, ephemeral data consisting of geophysical surveys and sediment coring in the offshore and back island lagoonal parts of the Bear Island, Onslow Bay, and Bogue Banks areas. These surveys will be taken in the same location of surveys and coring done for studies in the same areas prior to the storm to understand the impacts of Florence on these environments. Goals of the collection and analysis of the new data are to assess the impact of the storm on: (1) erosion and sedimentation throughout the region; (2) changes to the sand resources (location, volume, etc.); (3) changes to the types of microfossils and sediments in the various environments and; (4) the potential for retaining and identifying this storm signal in the stratigraphic record. Understanding inner shelf and coastal processes and their response to high energy storm events like Hurricane Florence is important for accurately calculating sand volumes for beach nourishment, understanding where sand goes following such an event, and forecasting coastal erosion rates in response to sea-level rise and storm impacts. This will aid in our understanding of the resiliency of sand resources which are vital for beach nourishment in this region and all along the Outer Banks of the United States. Broader impacts of the work include graduate and undergraduate student training and the sharing of data and information with Hammocks Beach State Park personnel in North Carolina which may aid in management of the park, as well as other coastal resource managers. Hurricane Florence severely impacted the coastal region of North Carolina between Cape Fear and Cape Hatteras in September of 2018 with sustained winds of 50 to 90 mph with gusts exceeding 100 mph. It also generated significant wave heights of 8 meters with peak periods of 15 to 17 seconds in a generally microtidal area. The hurricane also caused a storm surge of 2 to 3 meters in central Onslow Bay, North Carolina that was sustained over several tidal cycles. With an average inner continental shelf depth of about 15 m in Onslow Bay, these shallow water waves possessed tremendous energy that greatly influenced erosion, sediment transport, and deposition on the inner continental shelf, the shoreface, and barrier island and inlet environments. These impacts were manifest in a location where substantial geological and geophysical pre-storm data were recently acquired. These pre-storm data will serve as a baseline for measurements collected post-Florence in the same areas. Both geophysical (multibeam bathymetric surveys and CHIRP subbottom data) and sediment coring/sampling on the inner shelf and shoreface will be collected. Comparison of the pre- and post-storm results allow assessment of (1) erosion and sedimentation in the area; (2) changes in the distribution of beach nourishment sand resources on the inner continental shelf; (3) changes to foraminiferal assemblages which are important for paleoenvironmental and paleo storm studies; (4) assessment of the potential for survival and identification of storm signals in the stratigraphic record.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.