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Coastal Geology at Botany Bay WMA on Edisto Island

Long before the creation of Botany Bay WMA in 2008, the shoreline on the northern end of Edisto Island has been undergoing changes due to environmental conditions. The Edisto Island Open Land Trust invited South Carolina Department of Natural Resources geologist Katie Luciano to address their Back To Nature event on Saturday March 10. Aerial photos leave little doubt that the shoreline is receding at Botany Bay WMA, which is a normal cycle in barrier island geomorphology.

The coastal geology lecture was held in the meeting room at the Edisto Beach State Park Environmental Learning Center. Right beside the meeting facility is the Bache Monument Trail, where a historical marker from the 1850 U.S. Coast Survey by Alexander Dallas Bache is located. Bache was the grandson of Benjamin Franklin, and supervised placing survey markers to aid accurate measurements of changing coastlines in the future. There is a series of Bache monuments on Edisto with the West End located on the State Park and the East End located on Botany Bay WMA.
“Barrier Islands are very young in terms of geology,” said Luciano. “We date much of Botany Bay WMA coastline to the Holocene era which is just 11,000-years old. Shorelines can shift very rapidly, especially under the influence of hurricanes. In general, coastal geology is constantly dynamic, and sea level rise is a new factor which could accelerate erosion. We are already seeing old marsh and sand deposits being exposed on Botany Bay WMA, which harden due to the oxidation process.”

Bess Kellett works for SCDNR on Botany Bay WMA and reports seeing other recent changes that are indicators of erosion. Streaky orange sediments on the beach might be coming from groundwater flow that was out of sight under trees previously. The boneyard beach of dead trees on Botany Bay beach serves to underscore how land is changing over to beachfront. Kellet also reports a new outflow inlet from a winding tidal creek that is now coming into closer proximity to the front beach area. It is very likely that the same creek has had similar inlets over the life of this barrier island.

Luciano works for the South Carolina Geological Survey, with offices located at the SCDNR Marine Resources Division at Fort Johnson. She works on the Shoreline Change Project, creating digital shoreline datasets primarily from historical aerial imagery. These can be viewed in a time-lapse format to analyze the physical changes taking place along coastal South Carolina. This project focuses on managed properties like Botany Bay WMA, and is also able to utilize scientific monitoring data from the larger ACE Basin National Estuarine Research Reserve.

The S.C. Geological Survey hopes that mapping of past shoreline changes can aid better predict of future changes. Records now show that over the past 68 years, Botany Bay WMA has experienced one of the highest rates of erosion along coastal South Carolina. The shoreline has moved as much as three quarters of a mile inland, and similar movement is predicted through the year 2060 using online viewing tools.

An old pier, constructed of palmetto tree pilings, is now exposed on the beach at Botany Bay WMA near the North Edisto Inlet. We learned that Ocella Creek used to have an ocean inlet component near the area, but where the old pier actually led to is lost to time and to coastal geology. One can infer that other historical finds may be coming sooner rather than later as erosion continues at Botany Bay WMA. It’s good that SCDNR monitoring is in place to document these changes, so that more of the history of Edisto Island can be learned and preserved.

The Edisto Island Open Land Trust (EIOLT) has several upcoming events for those that wish to get involved. On April 21 join guide Tom Austin for a visit to the Roxbury Park in Meggett to explore native flora and fauna. EIOLT partners with Lindsay Young at Edisto Watersports for kayaking on May 19 and crabbing on June 16. Their annual I Love Edisto fundraiser dinner and auction is at 6:30 on June 23, and is always a grand occasion for conservation.

Jeff Dennis is a Lowcountry native. Read his blog at LowcountryOutdoors.com

Jeff Dennis, Contributor (341 Posts)

Jeff Dennis is a Lowcountry native. Read his blog at www.LowcountryOutdoors.com