COASTAL SALT-MARSH DEVELOPMENT AT SOUTHERN TOPSAIL SOUND, NORTH-CAROLINA

Topsail Sound is a marsh-filled barrier lagoon in southeastern North Carolina. This study quantified changes within a 477-ha tidal marsh located landward of Lea and Coke islands in southern Topsail Sound. Aerial photographs from 1949, 1966, and 1984 were enlarged, and sample areas of salt marsh were digitized and compared. Since 1949, Old Topsail Inlet has migrated southwest 1.2 km. As the inlet migrated, new Spartina alterniflora marsh colonized 33.2 ha of intertidal sand flats within the inlet flood tidal delta, adjacent islands, and primary tidal creeks. Landward of the flood tidal delta, site specific gains and losses of marsh were recorded. It is estimated that since 1949, approximately 34.1 ha of the marsh area occupying the zone landward of the flood tidal delta has drowned. This loss of marsh, combined with the colonization of marsh mentioned above, resulted in a net decrease of 1 ha in the total area of marsh. This study provides evidence that, although lagoonal marshes may be drowning as a result of soil waterlogging, reduced sediment supply, and sea-level rise, potential marsh environments are created by oceanic inputs of sand when inlets migrate.