TRACKING GEOMORPHIC EVOLUTION ON CORE BANKS, NORTH CAROLINA

Geomorphic classification and mapping of the NC barrier islands were part of the USGS-ECU-NCGS cooperative coastal research program in partnership with the USNPS and USFWS. Geomorphic classification was based on a barrier island evolution model developed from process-response studies and modern field surveys of the NC Outer Banks. The study utilized time-slice analysis of geo-referenced aerial photos (1932-2003) and topographic surveys (1852-2003) of Core Banks, Cape Lookout National Seashore, NC. LiDAR data are used to aid the mapping of geomorphic components.

Geomorphic features form and evolve in response to complex interactions between sea-level rise, storm dynamics, and human modification. Core Banks are narrow, sediment-poor barrier islands dominated by inlet and overwash processes. The Portsmouth and Cape Lookout sites each demonstrate different aspects of these processes. The Portsmouth site consists of a wide, low-lying microbial flat bounded by foredunes on the ocean and platform marshes on the estuarine side. The microbial flat was previously submerged during high-tide but, due to accretion of overwash sediment, is now supra-tidal with interior marsh grasses migrating across the microbial flat. Platform marshes are separated by tidal channels and decrease in size to the SW. Several historic inlets existed at the SW end of Portsmouth where their contributions to the geomorphic evolution of the island were traced in this study. Cape Lookout comprises the SW end of Core Banks and separates two coastal compartments, Raleigh Bay (NE) and Onslow Bay (SW). Cape Lookout forms a ‘hook' where oceanic overwash processes impinge from the E, S, and W and has in the past received substantial human modification by military activities and vegetation plantings. A hurricane severed Cape Lookout from Shackleford Banks in 1933, forming Bardens Inlet. The inlet, maintained by dredging, cut off the natural sand supply to Shackleford Banks and other barrier islands to the W.