Photo interpretation of shoreline changes between capes Hatteras and Fear (North Carolina)

Abstract

Sandy barrier islands of the Outer Banks of North Carolina form one of the coasts in the United States most exposed to modification by hurricanes and other major storms. Changes in coastal outline have been determined from: ( 1) aerial photographs dated 1945, 1953, 1955, 1958, 1959, 1961 and 1962; ( 2) U. S. Coast and Geodetic Survey charts and field sketches back to 1852; and ( 3) topographic maps. Areas chosen for detailed study are capes Hatteras, Lookout, and Fear; the coast near Ocracoke and Snow Marsh; and Hatteras and Beaufort inlets. During the period of aerial photography the shoreline has retreated at all three capes, but earlier capes Fear and Hatteras retreated, while Cape Lookout was extended seaward. The outlines of spits at the southern ends of the capes frequently change orientation in response to non-tidal currents produced by gale-force winds. Major storms are most important in modifying the configuration of the North Carolina coastline, but normal shore processes during periods of calm weather tend to redevelop the original smooth outline of the coast. Hurricanes caused erosion of the seaward side of the beaches and deposition of washover fans in the bays, so that the barriers migrated landward. During storms a part of the sediment is transported across the beaches to the bays; at other times it is moved southward by littoral currents (net drift direction); and some is lost permanently by being moved into deeper water at the cape points. Storm waves from the ocean side break across the low parts of sandy barrier islands to form washouts and inlets. At some times strong winds pile up lagoonal waters in one area so that they overtop the barrier, and drain across it to the sea. Inlets migrate southward in the direction of net littoral drift, and are often closed due to the shifting of the balance between littoral drift and tidal currents. Major inlets, such as Hatteras Inlet, migrate because of breaches in the downdrift side of the barrier and further erosion of the small detached islets formed thereby.