Barrier Island Response and Human Adaptation to Accelerated Sea-Level Rise, North Carolina Outer Banks

With visions of unlimited growth, the booming North Carolina coastal economy is on a collision course with natural processes that maintain the short-term health and long-term evolution of the coastal system. Data demonstrate the spatial and temporal history of the dynamics and evolutionary change of the Outer Banks based upon integration of 1) aerial photographic time-slice analyses, 2) seismic and ground-penetrating radar surveys, and 3) sediment and age analyses of drill cores. The Outer Banks consist of two island types. “Simple” barriers are low and narrow, weak links in the chain of eight isolated villages that extend south from the northern urban area. The urbanized areas often occupy higher and wider “complex” barriers. About 80% of the islands are sediment-poor, “simple” barriers consisting of paleo-inlet and overwash-plain sequences that formed within the last 1 to 2 millennia. The remaining 20% are sediment-rich “complex” islands composed of stacked beach ridge and back-barrier dune field sequences that formed between 3 to 5 millennia ago. Increased human modification, in concert with increased rates of local sea-level rise during the 20th century of 0.5 m/100 yrs, have promulgated ubiquitous shoreline recession and increased rates of collapse of many segments of “simple” barriers.

As the coastal system continues to deteriorate, demands to engineer a “permanent fix in time and space” are escalating, pitting the short-term economic gain against long-term natural coastal system dynamics. To maintain a vital coastal economy and preserve the natural resource base during accelerated sea-level rise, we must implement an adaptation plan. If a plan of differential retreat is implemented then the “simple” barrier segments can respond naturally to climate change, the Outer Bank villages will become like a string of pearls strung on a vast network of inlet and shoal environments with a series of Ocracoke-style destination villages.