SHORELINE EROSION ALONG BOGUE BANKS, NORTH CAROLINA

摘要

Bogue Banks, North Carolina, is a 25-mile (40 kilometer) long barrier island in the lee of Cape Lookout, midway between Cape Hatteras and Wilmington, North Carolina (Fig 1). It is oriented east-west and is sheltered from northeast storms by the cape. However, it is directly exposed to hurricanes and has sustained five land-fall tropical storms since 1996, the most recent of which was Floyd in September 1999. Historical shoreline recession rates have been low, with most estimates averaging about 2 feet per year (ft/yr) [-0.6 meters per year (m/yr)]. In contrast to many barrier islands, Bogue Banks has relatively high relief, reaching elevations greater than 50 ft (15 m). Typical foredune elevations are 16-33 ft (5-10 m) above sea level, and washovers are nonexistent. With an increased frequency of storms, Bogue Banks' erosion has accelerated and has led to extensive damage to the dune system, walkover structures, ocean piers, and many buildings. Damages from Hurricane Floyd along the oceanfront were estimated to range from $5 to $ 10 million. The present study determined that Floyd caused dune recession averaging 15 ft (4.6 m), accretion of the mean high water contour averaging 25 ft (7.6 m), and a maximum volumetric erosion for any reach of about 18 cubic yards per foot (cy/ft) [45 cubic meters per meter (m~3/m)]. Beach scraping combined with natural recovery after the storm restored the beach to prestorm conditions such that nine months later, there was negligible net loss in beach volume measured to approximate closure depth. The primary mitigation measures after each hurricane have been beach/dune scraping, reconstruction of walkovers, and emergency sandbagging. Only a few houses have been relocated. The recent erosion experience at Bogue Banks has sparked debate regarding what course of action to take-whether to abandon property, relocate, or rebuild the beach.