RESPONSE OF WETLANDS TO RISING SEA-LEVEL IN THE LOWER COASTAL-PLAIN OF NORTH-CAROLINA

Most of the coastal wetlands of the South Atlantic region of the United States are expected to diminish in size in response to the opposing forces of increasing human population growth and accelerating rates of rising sea level. We evaluated several models that project the response of coastal wetlands to rising sea level and concluded that current models appear unsuited for wetlands of the Albemarle-Pamlico peninsula of North Carolina. We came to this conclusion after we examined the distribution of wetlands, elevation contours, estimates of surface slope, soil types, and peat deposits on the peninsula. Most of the data were obtained from U.S. Geological Survey topographic quadrangle maps, U.S. Fish and Wildlife Service National Wetlands Inventory maps, U.S. Soil Conservation Service soil surveys, and inventories of peat deposits. Some unusual features of this peninsula are low elevation (56% of total area <1.5 m), extensive coverage by wetlands (53%) and hydric soils (90%), negligible slopes of the land surface, virtual absence of tides, and lack of abundant sources of sediment. In the process of reconstructing how past rises in sea level most likely led to present conditions, it became apparent that vertical accretion of peat in situ is largely responsible for landscape features in areas where elevations are lowest. Were it not for these deposits, the land surface area of the peninsula would be decreasing relative to sea level. This situation contrasts sharply with areas in the eastern United States fringed by tidal marshes, which are undergoing overland migration at a rate dictated by landward slope and the rate of rising sea level. If the rate of sea level rise accelerates, it is doubtful if vertical accretion rates of peat can prevent submergence of extensive areas of wetlands in the Albemarle-Pamlico peninsula. Land use and drainage in the lowest elevations of the peninsula are currently being affected by sea level. Future land management of the peninsula will be constrained by potential landscape changes as a result of rising sea level.