THE IMPACT OF HURRICANE ISABEL ON SHACKLEFORD BANKS, NC

Hurricane Isabel struck the North Carolina coast in the early afternoon of September 18, 2003, midway through 2 years of dissertation fieldwork investigating beach-dune-nearshore interactions on Shackleford Banks, NC, a 15km long barrier island located in the southern Outer Banks. Detailed monthly GPS surveys and a post-hurricane survey bracketed the event, and deployment of 3 S4A electromagnetic current meters captured important offshore data. Together these data provide valuable information about the effect of the storm on hydrographic conditions, the amount and type of impact on the island, and rates of recovery at different locations with varying morphologies.

Although Isabel made landfall on nearby Core Banks, Shackleford and other areas to the southwest of the eye were impacted less severely than areas to its north and northeast. Shackleford’s northwest-southeast island orientation and its protected position “behind” Cape Lookout also helped to mitigate storm effects. However, significant changes did occur. Scarped foredunes near the inlets on the island’s ends and along ~ 2km of beach on the eastern half of the island eroded up to 6m more in places. In many areas, the beach lost a great deal of sediment, but the backbeach of much of the west-middle section of the island accreted. “Recovery” in the months following the storm varied greatly. Some areas returned to profiles similar to those present pre-storm, or similar to the same month the prior year, while others retained their post-storm shape, or continued on a trend started by the event.

The current meters were moored along the island at depths of ~ 4m. The westernmost meter stopped collecting data prior to the storm. The middle meter withstood instantaneous NE-SE currents up to 570 cm/sec and wave heights of 3m on the night of the 17th, before being toppled at 12:42 PM on the 18th. The eastern meter, in a location typically experiencing slow SW-NE currents and waves less than 50cm high, recorded instantaneous S-SE storm currents up to 230 cm/sec and wave heights reaching 3m shortly after 2:00 PM on the 18th.

Variability in response and recovery will be discussed in greater detail at the conference, incorporating additional data from the coming months and further processing of the S4A time series records.