Washover Volume Analysis of Hatteras and Pea Islands, North Carolina, USA over Centennial Timescales

Hurricanes (tropical cyclones) and nor’easters (mid-latitude cyclones) are high-energy storms often impacting the Outer Banks (OBX) barrier islands of North Carolina (NC), USA. Storm hazards include, but are not limited to, high speed winds, coastal flooding, storm surges, and increased precipitation. As a consequence of increased storm strength and frequency, loss of life, property damage, and erosion to beaches, barrier islands, and marshes have amplified over the past 40 years. In a recent report by the National Oceanic and Atmospheric Administration (NOAA), US taxpayers expended ~$1.05 trillion on hurricane and nor’easter impacts from 1980 to 2020. Identifying historical hurricanes and nor’easters in the geologic record as washover deposits can aid in the understanding of past events and prediction of future impacts to the OBX. Storm events yielding washover deposits can be identified, mapped, and quantified using various geologic, geophysical, and remote-sensing techniques. To identify both modern and historic coastal storms, nine sediment cores and 2300 meters of ground penetrating radar (GPR) data were collected, and five trenches were dug from the surface to the water table on three washover fans on Hatteras and Pea islands, NC. Grain size distributions were measured at centimeter intervals from trenches and sediment cores. GPR data were used to map spatial extents and measure sediment thicknesses in washover deposits down to ~1 m. Radiocarbon and short-lived isotopic dating techniques were employed to ascertain ages of washover deposits identified within cores. Additionally, historical surface analyses, hurricane tracks, and buoy data from NOAA were used to correlate washover deposits to known historic and modern hurricanes or nor’easters. To date, this project has identified several discrete washover events associated with Hurricane Sandy (2012) and several nor’easters across the northern (Pea Island) and middle/southern (Hatteras Island) study sites. Radiocarbon dating from plant material indicates these sites contain a ~500 cal yr BP record of washover deposition. The significance of this project is to evaluate differential impacts of nor’easters and hurricanes on the geomorphic evolution of Pea and Hatteras islands through the integration of data from multiple methodologies.