Variations in Inlet Behavior and Shoreface Sand Resources: Factors Controlling Management Decisions, Figure Eight Island, NC, USA

Although beach nourishment is considered the only viable option for maintaining oceanfront beaches, the prohibition of large-scale mining of mainland sites and estuarine channels has made it difficult for communities with severe erosion problems to plan mitigation. Figure Eight Island, North Carolina, is an example of a community where erosion during the past decade has increased dramatically due to the combined effects of the bordering inlets and the impacts of recent hurricanes. The chronic erosion has prompted a system wide investigation aimed at inventorying the offshore sand resources for long-term management of the oceanfront beach. The contrasting behavior patterns of Rich and Masons Inlets, which form the island's northern and southern boundaries respectively, have influenced historic shoreline change patterns. Although Rich Inlet has been relatively stable, the ebb channel has shifted repeatedly; and as a consequence, reconfiguration of the expansive ebb delta has led to severe erosion along a 2 km reach downdrift of the inlet. Mason Inlet is a small migrating system whose soundside channels have shoaled since the mid 1990's, resulting in a dramatically reduced tidal prism and increased migration rates that exceeded 140m y−1. Migration and consequent realignment of the trailing barrier resulted in oceanfront erosion that extended for 3 km updrift. Relocation of the inlet is planned for early 2002. Less than 10% of the 4.0 million m3 needed for nourishment will be available as a result of the relocation efforts. Although the shoreface has been viewed as a potential borrow source, data indicate it has a low potential for providing significant volumes of quality sand. The lack of shoreface sand resources and the minor amount available from future dredging activities at Mason Inlet strengthens the need for developing a sound sand management strategy for Rich Inlet for long-term maintenance of the oceanfront.