Kiawah Island east end erosion and beach restoration plans Posted April 25, 2006
CSE was retained in May 2005 by the Town of Kiawah Island to assess a major erosion problem along the world-famous Ocean Course at the east end of the island. Since 2000, parts of the Ocean Course have lost nearly 400 feet of dunes. Emergency sand scraping was implemented by the club to protect the service roads and irrigation systems. However, this stop-gap measure has not been sufficient to keep pace with erosion.
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Overhead view
From east
From west
Dr. Tim Kana, CSE's president, has studied Kiawah Island since the 1970s. Along with colleagues from the University of South Carolina, Kana identified an ~7-year cycle of shoal bypassing that controls the stability of Kiawah's east end. Shoal bypassing is the episodic release and landward migration of sand bars from ebb-tidal deltas (cf, Kana, Hayter & Work 1999, Gaudiano & Kana 2001, referenced in "Publications" under "Our Firm"). Bypassing events in the 1990s were much larger than any others to date, adding upward of five million cubic yards to Kiawah Island. The sizes of the shoals that attached to Kiawah were enough to create a new barrier island/lagoon system almost three miles long and a half-mile wide. Where open ocean conditions existed barely ten years ago, there is now a barrier beach, sheltered lagoon, and incipient marsh. All this bodes well for Kiawah in the long run. However, the short-term effect of these changes has been rapid erosion along the Ocean Course.
Initial emergence of a sand bar at the downcoast flank of an ebb-tidal delta and migration onshore under the influence of breaking waves.
Attachment of the shoal to the beach at low water, leaving a massive bulge in the shoreline which alters waves and sand transport. The beach areas adjacent to the points of attachment tend to erode rapidly during stages 1 and 2.
Continued onshore migration of the shoal accompanied by lateral transport of sand to downcoast and upcoast areas. Waves attack the bulge produced by the sand bar and spread the sand along the beach.
Shoal-bypassing cycles can occur over a range of time scales from less than one year to more than a decade. In the present case, the cycle is expected to be well over ten years, simply because there is so much sand to move.
CSE prepared an innovative plan for addressing erosion along the Ocean Course based on the natural, shoal-bypass cycle. Sand from the accreting shoal will be removed and hauled to downcoast areas. This is similar in concept to another CSE project at Isle of Palms in 1984. The difference this time is scale and the need to safeguard certain habitats that have attracted threatened species such as piping plovers. The proposed project calls for moving 360,000 - 550,000 cubic yards about one mile south. It also includes construction of a new flushing channel through the center of the accreting shoal and closure of the existing channel.
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Click for work plan
Click for proposed beach
CSE worked closely with Kiawah's town council and staff wildlife biologist, USFWS, and SCDNR to develop an environmentally sensitive plan. The state permit, applied for in November, was received on March 21. We anticipate starting construction by May, pending receipt of the federal permit. For this project, the resource agencies requested a later construction start date to safeguard overwintering areas for plovers. The town and contractor (not yet selected) will be implementing extensive environmental monitoring to safeguard turtle nesting activities.
For more information, contact Jim Jordan, Kiawah's wildlife biologist at 848-768-9166, or Dr Tim Kana at CSE's Columbia office.
