SHORELINE RECESSION IN RESPONSE TO RECENT HURRICANES AND IMPLICATIONS FOR BOTH MANAGEMENT AND EVOLUTION OF BARRIER ISLANDS DURING RISING SEA LEVEL

North Carolina experienced at least 47 hurricanes during the 20th century, in addition to abundant tropical and extra-tropical storms such as the Ash Wednesday (1962) and Halloween (1991) storms. The 12-year interval from 1993-2005 was the most active storm period in recorded NC history with eleven hurricanes (all category 1-3 storms), including four during the past three years (Isabel, 2003; Alex and Charley, 2004; and Ophelia, 2005), that directly impacted the NC coast. In spite of the smaller size of these storms, severe cumulative geological impacts occurred to the coastal system. To evaluate the barrier island processes and responses to individual storm events and storm periods, three methodologies were utilized: a series of cross-island topographic surveys (1960-2001); time-slice analysis of georeferenced aerial photo sets (1932-2005); and field mapping of island morphologic features (2000-2005).

Integration of long- and short-term shoreline change data with time-slice analyses, and field mapping leads to the following conclusions. 1) Storm-driven shoreline erosion on barrier islands is intimately associated with inlet and overwash dynamics, both of which significantly increase island width and elevation with increased vegetative cover through time. 2) Most human modification attempts to stop or minimize normal storm impacts (shoreline recession, inlets, and overwash) severely jeopardize the long-term health of barrier islands during rising sea level. This, in turn, greatly increases the risk to urban development and possibilities of barrier-island collapse in response to category 3-5 storms. 3) Short-term shoreline change data demonstrate that individual storms result in large-scale recession, whereas during non-stormy periods shorelines can partially and temporarily recover if given enough time between storms. However, storm frequency generally does not allow complete post-storm recovery before the next storm(s) arrive. 4) Long-term recession rates integrate both low- and high-storm periods resulting in a low net recession rate that can be extremely misleading when utilized for management purposes. Since shoreline recession is storm-event driven, recession from an individual storm generally exceeds minimal setbacks and results in severe property losses.