Barrier Islands

Barrier islands, which run parallel to the Atlantic and Gulf coasts, are so named because they shield the mainland (as well as inland Sea Islands) from damage caused by sea storms. South Carolina has thirty-five barrier islands, more than any other state except Florida. Among South Carolina’s major barrier islands (from north to south) are Waites, Pawleys, Debordieu, North, South, Cedar, Murphy, Dewees, Isle of Palms, Sullivan’s, Morris, Folly, Kiawah, Seabrook, Botany, Harbor, Hunting, Fripp, Hilton Head, and Daufuskie. Hilton Head, the state’s largest barrier island, actually consists of an erosion remnant island as well as a barrier island; the two are separated by Broad Creek.

Two types of Sea Islands border the South Carolina coast: barrier islands and erosion remnant islands. Located inland from the ocean, erosion remnant islands originally were part of the mainland. When Ice Age glaciers lowered sea levels, streams cut river valleys into the newly dry land. But once the glaciers melted, the ocean level rose and flooded the river valleys. Less is known about the creation of barrier islands, and two theories exist regarding their origin. The first argues that barrier islands began as offshore sandbars, which waves built up with sand deposits. The second theory suggests that they are sand dune ridges remaining from the big glacier meltdown.

Barrier islands tend to possess an elongated shape. In general, the northern end is longer than the southern end, which is constantly affected by erosion. While varying in size and shape, all barrier islands generally share certain characteristics. Each is shaped by ocean surfs, which constantly shift and erode their beaches. Grassy dunes occupy the terrain immediately behind their beaches, while the interior of barrier islands is dominated by maritime forests and wetlands. Most barrier islands possess lee or bayside salt marshes that face the mainland. Besides protecting the coastlines, barrier islands provide crucial habitats for vital flora and fauna such as algae, sea oats and bitter pancum, sawgrass, crabs, offshore and inshore fish, snakes, deer, raccoons, opossums, sea turtles, and sea fowl. These salt marsh ecosystems also act as filters, purifying runoffs from inland waterways. Unlike the more stable inland Sea Islands, barrier islands–which border the ocean–are dynamic; their terrain is constantly changing. Despite this inherent instability, South Carolina’s barrier islands were heavily developed throughout the latter half of the twentieth century as vacationers made their beaches popular tourist attractions.

The histories of Edingsville Beach and Morris Island perhaps best illustrate the fragile and dynamic nature of barrier islands. Edingsville, off Edisto Island, once supported a bustling summer vacation village, until a hurricane in 1893 swept away much of the island. Since then, the island has remained a sandy bar, supporting primarily only shrubby growth. Morris Island’s rapid erosion is attributed to Charleston harbor’s jetties. In the late nineteenth century the Morris Island Lighthouse sat 2,700 feet inshore. A century later it stands approximately 2,000 feet offshore.

Ballantine, Todd. Tideland Treasure. New ed. Hilton Head, S.C.: Deerfield, 1991.

Lennon, Gered, et al. Living with the South Carolina Coast. Durham, N.C.: Duke University Press, 1996.

Murphy, Carolyn H. Carolina Rocks! The Geology of South Carolina. Orangeburg, S.C.: Sandlapper, 1995.