GIS MAPPING OF BARRIER ISLAND LANDSCAPES OF THE NORTH CAROLINA OUTER BANKS USING LIDAR TOPOGRAPHY AND DIGITAL AERIAL PHOTOGRAPHY

Cape Hatteras and Cape Lookout National Seashores, which encompass most of the North Carolina Outer Banks barrier island system, were mapped using remotely sensed digital data. The primary data layers used are 1998 color infrared (CIR) aerial photography (1:12,000 scale) and high resolution topographic data derived from a recent Light Detection And Ranging (LIDAR) survey. LIDAR elevation data (20 cm vertical and 1 m horizontal resolution) were downloaded as 20-foot Digital Elevation Models (DEM's)from the North Carolina Floodplain Mapping program website (www.ncfloodmaps.com) as 10,000- by 10,000-foot tiles (500 row x 500 column text files). Once downloaded, the DEM files were converted to raster grids, mosaiced, and then clipped with a digitized shoreline.

Mapping covers approximately 210 km of barrier island system. This includes barrier island segments with well-developed beach ridge complexes as well as segments dominated by overwash processes. Numerous tidal inlets occur within the map area and several former inlets are known from historical accounts. A wide variety of both modern and relict subaerial and submarine geologic environments form distinctive landforms that are mappable via “heads-up” digitizing using Geographic Information System (GIS) software and digital data layers. Map units include marsh, overwash fan, flats, dunes, dune ridge, beach ridge, beach, ridge and swale topography, back barrier berm, and various human impacted features among others.

The map produced by analysis and interpretation of these data layers in GIS is a significant improvement over existing maps. The relationships, form, and patterns of the mapped features indicate what geologic processes have been active recently and allow prediction of the future impacts of some of these processes. The map will also serve as an effective resource management tool for the National Park Service. Refinement through ground truthing and integration with an ongoing regional geologic framework research program for the geology of the northeastern North Carolina Coastal Plain and inner Continental Shelf will improve the mapping even further.