24 Coastal and Marine Sedimentary Geology in the Southeastern United States: A Session in Honor of Dr. V.J. "Jim" Henry

Friday, 30 March 2007
8:00 AM - 5:20 PM

BARRIER PLANFORM CHANGES RELATED TO INLET MIGRATION AND SHORELINE ARMORING: EAST BEACH, NC

Paper number: 24-18
Program: SYMPOSIA SESSIONS
Time: 2:40 PM – 3:00 PM

Authors

Abstract

East Beach, a narrow 10 km long barrier that connects the Fort Fisher headland and the Cape Fear Foreland, has been breached numerous times during the past centuries. Prior to 1880 the storm breaches served as one of several conduits for the exchange/discharge of the Cape Fear River. One long lasting breach that opened in 1761 near the headland evolved into the second largest inlet system in the area until it was artificially closed by the USACE in 1880. Closure was accomplished by the construction of a 4.6 km long dam that dramatically reduced the tidal prism and the extent of the ebb tidal delta. Long lasting impacts associated with inlet closure include the chronic erosion of the headland area and frequent breaching of the barrier and the subsequent rapid migration of small inlets. Concurrent with inlet migration is the realignment of the barrier spit shoreline. In an effort to mitigate the chronic headland erosion occurring updrift of the East Beach barrier spit attachment, a 1km long revetment was constructed by the USACE in 1994.

The most recent cycle of inlet breaching, migration and closure occurred in the years 1944 – 1999. During this period New Inlet migrated a total of 6 km, averaging 112 m/yr. Migration rates varied from a high of 271 m/yr (1945 – 49) when the inlet was at its northern most position, to a low of 33 m/yr (1974 – 86), when the inlet was located along the southern extent of the spit. Significant shoreline repositioning, due to inlet migration, was commonplace along the spit. Between 1954 and 1974 the mid- barrier reach prograded 240m as the inlet migrated to the SW. In contrast during the subsequent two decades only 20m of erosion occurred along the same shoreline reach. The impact of updrift shoreline armoring is also evident along the mid-barrier reach, where 100m of erosion occurred within a three-year period between 1996 and 1999. Chronic erosion continues to date.