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