TIME-SLICE ANALYSIS AND GEOMORPHIC MAPPING HELP UNRAVEL BARRIER ISLAND EVOLUTION: CAPE HATTERAS AND CAPE LOOKOUT NATIONAL SEASHORES, NORTH CAROLINA

Geomorphic classification and mapping the North Carolina barrier islands is part of the ongoing USGS-ECU-NCGS cooperative coastal research program in partnership with the USNPS and USFWS. The geomorphic classification is based on a model of barrier island evolution developed from process-response studies and modern field surveys of the NC Outer Banks. Modern data are integrated with historical data to develop the evolutionary responses of geomorphic-ecologic systems to sea-level rise, storms, and human modification. LiDAR data are used to aid in mapping the geomorphic components. The detailed studies utilize time-slice analysis of geo-referenced aerial photographs (1932-2003) and topographic surveys (1852-2003) for specific sites between Kitty Hawk and Cape Lookout, NC. Time-slice analysis is a crucial tool that enables documentation of time of origin, as well as the evolutionary development of present barrier island features. Many features formed 150 years ago by one set of processes and have been modified through time by other sets of processes to produce the complex features being mapped today. The geomorphic classification is based on a simple inlet- and overwash-dominated barrier island model and contains five main features and series of sub-features. The main model components include the Beach, Overwash-Plain, Polydemic, Anthropic, and Sound Features. In differentiated geomorphic units, the dominant vegetation type associated with that unit is part of the geomorphic name. Complex barrier islands are comprised of active, simple barrier islands that have welded onto older, pre-existing barrier island segments; the latter are generally dominated by beach-ridge and swale deposits. This study demonstrates the substantial impact that storms and human modification over the past 150 years have had on the evolution of the modern NC barrier islands. Mapping the evolution of the geomorphic features through time also helps in delineating the most ‘vulnerable' segments of the Outer Banks.