DYNAMIC PROCESSES SUSTAIN OUR NATIONAL PARKS AND REFUGES WHILE SEA LEVEL RISES: NORTH CAROLINA OUTER BANKS

Two-thirds of North Carolina’s Outer Banks barrier islands, from Virginia to Beaufort Inlet, are Federal Lands. These include Cape Hatteras and Cape Lookout National Seashores and Pea Island National Wildlife Refuge. In the 1920s-30s, predominantly low and narrow (simple) barrier island segments were designated as federal seashores and refuges, and the wider (complex) island segments remained in private hands and are now urbanized. Narrow island segments are generally sand-poor, inlet and overwash prone and, where they connect villages, accommodate the coastal highway. These dynamic island segments are particularly vulnerable to increases in storms and sea level.

Geomorphic mapping of selected sites along the Outer Banks elucidated the processes responsible for generating the geomorphic features, and led to development of a classification and model for barrier island evolution. The mapping and classification were based on process-response studies, field surveys, time-slice analysis of geo-referenced aerial photographs (1932-2003), LiDAR data (2001), and historical topographic surveys (1849-1917). These studies demonstrated that storm overwash and inlet formation are critical to the evolution of simple barrier islands during sea-level rise. Additionally, island geomorphology and geometry are functions of the geologic framework, sediment supply, sea-level changes, and storm characteristics.

Simple barrier-island segments are dynamic; they vary in width and volume over time and transgress with rising sea level. On those barrier segments not manipulated by humans, such as Core Banks, elevation, width, and transgression are maintained by the storm dynamics of inlets and overwash. Human modification, however, interferes with these processes. Thus, it is recommended that storm dynamics be allowed to operate naturally to ensure the continued existence of these simple barrier island segments. This policy should be consistently applied as the preservation of these Seashores and Refuges on the Outer Banks is jeopardized by efforts to preserve their function as transportation corridors. In contrast, Cape Lookout National Seashore, a relatively unmodified barrier system with access by ferries and with alternate island transportation, provides a model for sustainable barrier island management.