Tomorrow, Dr, Leslie Sautter of the College of Charleston is coming over to Dewees to give a presentation about the predictable, and unpredictable changes to our shoreline. Please join us at the Huyler House at 11:30 for a brown bag lunch presentation! Dr. Sautter has been leading a long term study of our changing shorelines on Dewees, and part of that is an aerial flyover program with the Dewees Island Conservancy. The most recent flyover was in January. Tomorrow she will talk about our shoreline: accretion and erosion, and share a lunch with us as she explains her findings. I asked her for some quick historical background on the program:
It was started in 2006 to give us perspective on the way our coast changes, somewhat predictably, due to along-shore currents, and unpredictably due to climate change or other events. The geomorphology study began on Dewees by David Betenbaugh and LRS as part of David’s Masters of Environmental Studies thesis from CofC. Initially, surveys were conducted 4 times each year to assess seasonal changes in the beach. Initial funding came from the Barrier Island Trust. Since the initial 3 years, annual surveys have conducted supported by funds from DI property owners and, most recently, the Dewees Island Conservancy.
Flyovers are especially helpful if we perceive from the ground that this is an erosion phase; we can look and see the vast stores of sand that will head our way during an accretion phase, because they provide us time to study and plan with larger perspective.
This photo, taken in January shows how the beach is growing, with a lot of the accreted land near the sand bar on the north end of the island.
In 2006 the shoreline was in a long phase of accretion and numerous dunes had grown seaward. By 2009, however, most of the accreted sand had eroded, as the island had entered a significant phase of erosion. This unexpected change was due to a large submerged sand body (“shoal”) off the northeast end of the beach. The shoal’s origin was the enormous tidal delta that sits offshore of Capers Inlet, on the north end of Dewees. Periodically, huge segments of the delta detach, using the constant but variable wave energy attacking them. As the shoal migrated towards the beach, it caused the waves to refract, or bend and redirect, so that the normal north-to-south alongshore flow of sand was interrupted. After several years, this same shoal has migrated landward and welded onto the beach, generating a huge bulge in the shoreline. Now the shoal is providing a tremendous volume of sand that is contributing to the downdrift beach, repairing some of the erosive damage done previously. Several other shoals have detached from the tidal delta and coalesced since the survey’s inception. They are also making their slow march landward. Dewees will soon have plenty of naturally accreted sand to reestablish its lost dune fields.
I asked Dr. Sautter how the department uses the research:
This long-term study has been unique in that we’ve “caught” an entire cycle of erosion-accretion due to a shoal attachment. The detailed annual surveys plus photographs from the air and beach perspectives have provided invaluable information that we plan to publish in the near future. This project has also been particularly important for providing opportunities for education, field experience and research for hundreds of undergraduate students and tens of K12 teachers.
The flyovers are funded by donations to the Dewees Island Conservancy. Sometimes community members go along. Here is Dr. Sautter preparing for takeoff with one of our intrepid members:
Can’t wait to learn more tomorrow at Huyler House, 11:30 am.