DEVELOPING A POTENTIAL INLET INDEX TO QUANTIFY VULNERABILITY OF THE NORTH CAROLINA OUTER BANKS

In 2003, Hurricane Isabel opened an inlet on the Outer Banks of North Carolina just west of Frisco on Hatteras Island, isolating Hatteras Village. This island inlet and the recent hurricane impact on the northeastern Gulf coast barrier islands demonstrate their susceptibility to significant short-term geomorphic change.

The goal of this research is to develop a series of indices to quantify the vulnerability of the North Carolina Outer Banks to inlet formation. It is hypothesized that island characteristics (e.g., volume, stratigraphy, and morphology) play key roles in determining where potential inlets may occur and can be used to predict vulnerability to future events. This research is developing methodology to identify inlet vulnerability in comparison to the site where the Isabel Inlet opened.

The vulnerability indices utilize a combination of remotely sensed data (i.e. aerial photographs, LIDAR), ground-penetrating radar (GPR) and direct subsurface documentation (e.g., cores). Digital elevation models of the Outer Banks are used in ArcGIS software to determine mean island width, height and volume along shore-normal transects. Overland flow patterns are simulated using the ArcHYDRO toolbox to evaluate flow focusing. Stratigraphic examination is based upon GPR surveys, hand augering and drilling. Stratigraphic data are used in conjunction with aerial photographs and elevation data to identify the presence of erosion-resistant subsurface peat platforms. Each index highlights the vulnerability of the Isabel Inlet area prior to the arrival of Hurricane Isabel and can be used to evaluate other areas of risk along the Outer Banks.