RECOVERY OF CARBONATE SAND BEACHES ON SAN SALVADOR ISLAND, BAHAMAS, FROM DAMAGE BY HURRICANE FRANCES (2004)

East Beach and Hanna Bay Beach, located on the northeast coast of San Salvador, were two of the island’s beaches most heavily impacted by Hurricane Frances (category 3) on September 2, 2004. A maximum storm surge of 3.1 m was reported for East Beach, with erosion occurring up to 70 m inland from the wave-break line and resulting in scarps cut into dunes of at least 1.3 m height. In January 2005, 5 beach profile stations along 1 km of East Beach and 3 stations along Hanna Bay Beach were established to monitor long-term recovery from hurricane damage. Both beaches were profiled 6 times using the stake and horizon method, beginning in January 2005 through January 2010. Dune vegetation also was greatly damaged by Hurricane Frances, and its recovery and stabilizing effects on dunes was recorded.

Each profile station revealed a somewhat different history over the study period. East Beach #1 exhibited a steep dune scarp almost 1.5 m high in January 2005. Subsequent profiles through January 2010 documented slumping of the original scarp and formation of an embryonic primary dune between 2008 and 2010. Other stations recorded different morphologies and varying degrees of recovery from wave-erosion scarping. Overall, East Beach stations showed sediment accumulation between 2005 and the present, with stabilization of the primary dune by vegetation. This is consistent with earlier studies that found East Beach to be progradational. Hanna Bay Beach profiles documented a similar pattern of primary dune recovery and showed smooth seaward slopes with minor degrees of sediment fluctuation. All stations manifested recovery of flora; Uniola paniculata (sea oats) is ubiquitous on dunes, and the coastal colonizer shrubs Borrichia arborescens (silver sea oxeye), Coccoloba uvifera (seagrape), and Scaevola plumieri (inkberry) are dominant species.

Both beaches have a history of progradation over the past ~3 thousand years, indicating an offshore sediment supply more than adequate to keep pace with slowly rising, late Holocene sea level. With accelerated sea-level rise predicted for the tectonically stable, subsiding islands of the Bahama Archipelago, future progradation for beaches on San Salvador may be in doubt. This likely already is true at narrow Hanna Bay Beach where progradation was negligible.