13 Sea Level in the Southeast: Past, Present, and Future

Thursday, 29 March 2007
1:20 PM - 5:00 PM

TWO DECADES OF SHORELINE RETREAT ON THE NORTH AND EAST SIDES OF ST CATHERINE'S ISLAND, GA

Paper number: 13-7
Program: THEME SESSIONS
Time: 3:20 PM – 3:40 PM

Authors

Abstract

St. Catherine's Island, GA, is a Holocene-Pleistocene barrier island with no artificial structures on the beach. Erosion of the east and north shores, augmented by accelerated sea level rise, was documented in the 1970s by McLain. The work has been expanded during the past 20 years to include more than 25 stations. At Engineer's Road on the north shore, a 0.8 m/yr southward migration of the beach into a forested Holocene dune field has left dead standing pines below the high tide mark. Growth of a large sand bar at the northeastern tip of the island has coincided with up to 20 m of lateral accretion below a 5 m-high Pleistocene bluff on the northern stretch of the east shore. In contrast, the southern 0.7 km-long stretch of this Pleistocene bluff has eroded at rates ranging from 1.3m/yr to 2.4 m/yr.

South Beach extends 4.8 km southward from McQueen's Inlet and has the highest rates of erosional retreat. Flag Pond was breached by 10.4 m of lateral erosion during a 1992 winter storm, and its freshwater flora has been replaced by saltwater species. Retreat of 2.1 m/yr at Beach Pond over the past six years has made the breach of this last fresh water pond along the eastern shore imminent. Washover of beach sand into marshes is common along much of South Beach, Middle Beach, and North Beach, resulting in exposure of marsh muds on the beach face as erosion progresses inland.