MORPHOLOGY OF THE SUBAERIAL CAPE POINT AT CAPE LOOKOUT, NORTH CAROLINA

Processes controlling the morphology of cape-attached spits along the coast of North Carolina involve both the submerged, cape-associated shoals and the subaerial cape headland. Direct observation of waves, currents and bathymetry on the shoals is extremely difficult and often hazardous. This reconnaissance study uses the changing geometry of the subaerial headland as a simple, easily observed proxy for complex nearshore sediment transport processes at capes. Real-time-kinematic GPS mounted on an all-terrain vehicle was used to generate high-spatial-resolution maps of Cape Lookout, North Carolina. The cape point responds rapidly to changes in nearshore wave height and direction. On the Core Banks (eastern) flank of the cape point, the dominant alongshore sediment transport direction is to the south during nor’easters, and creates a south-southwest pointing sand spit that can extend 50 m or more past the cape point baseline. On the other hand, during southerly swell conditions, southeast-directed alongshore transport may extend the western flank of the cape point to the southeast 150 m past the baseline. During October to December 2000, the point gained approximately 18,000 cubic meters of sand or roughly 5% of the volume of the point; at the same time, the area of the point increased by 34,000 square meters, or roughly 10%. Wind energy and direction during significant wave events are strongly correlated with changes in the location of the cape point, orientation of headland spits, surface area and total volume of sand contained in the point. We can exploit these relations to estimate the magnitude of longshore transport at sharp discontinuities in the coastline. In particular, on-going studies of Cape Fear on Bald Head Island will be used to monitor longshore transport of renourishment sand from the Wilmington Harbor dredging project.

Supported by the Terrestrial Sciences Program of the Army Research Office, Bald Head Island Conservancy and National Park Service.