Interdisciplinary Applications for Identifying and Quantifying Modern Storm Washover Deposits on Pea Island, North Carolina, USA

Abstract

Hurricanes and nor'easters annually threaten or impact the North Carolina (NC) Outer Banks, generating significant destruction to infrastructure, habitat, and life, while costing taxpayers thousands to billions of dollars. The geologic record (i.e., washover deposits) of these storms can be used to better understand past frequency and magnitudes, and aid in resource cost estimations for post-storm recoveries and clean-ups. Therefore, understanding washover rates and their influences on barrier island evolution is of critical importance. To identify and map recent storm washover deposition on Pea Island (PI), NC, for the period of 2003–2019, meteorological records, aerial photographs, lidar digital elevation models, ground penetrating radar (GPR) data, and sediment from trenches and cores were collected and analyzed. Hurricanes Isabel (2003), Irene (2011), and Sandy (2012), and three nor'easters (2006, 2009, and 2018) impacted PI during the study period, yielding washover deposits to the backbarrier. To quantify the storms' washover sedimentology and annual sand deposition rates, radiocarbon ages, washover thicknesses, and volumes were utilized on three distinct PI washover fans. These six storms yielded ∼9 × 10⁴ m³ of total washover in the study areas combined, with Isabel contributing 38.4%, Sandy contributing 35.8%, and the remaining storms contributing 25.8%. The washover deposition rate was at least ∼5.6 × 10³ m³/yr for the study period, an increase of 40% over the previous period of 1996–1999 at two comparative sites. This research highlights PI's vulnerability to repeated future storm impacts and provides stakeholders with quantifiable data with which to allocate future post-storm resources.