The Changing Outer Banks

Ask almost anyone in the country to describe North Carolina’s Outer Banks and they could probably name a few images easily — the Cape Hatteras Lighthouse, the wild horses, wide strips of sandy beach, and the Wright Brothers monument.

The Outer Banks are so ingrained into our collective national consciousness that people can visualize the coastal region without ever visiting it. The irony is that while images of the Outer Banks remain the same, the islands are constantly changing. They are supposed to.

Barrier islands are designed to move in response to storms and rising sea levels. In fact, Dr. Stanly Riggs, a coastal geologist at East Carolina University, says about 20,000 years ago North Carolina’s Atlantic coastline was 15 to 40 miles east of the current coast. That’s because so much water was locked up in ice sheets that sea level was 400 feet lower than it is today.

Riggs estimates some form of barrier islands first appeared off the coast about 7,000 years ago, as the seas began to rise after most of that ice had melted. The islands moved naturally westward and, as sea level rise slowed, the current version of the famous Outer Banks’ barrier islands began forming about 2,000 years ago. 

The movement is gradual. As storms slice through narrow, low-lying islands, the ocean water dumps sand on the western side of the islands. All the while, wind and waves constantly move sand across the island. As the ocean side erodes and the sound — or western side — grows, the islands move westward. The islands slowly roll over themselves. Riggs suggests it’s similar to the image of a bulldozer tread.

Not much changed for years, but now that scientists say the seas are rising again the islands should resume their gradual westward movement to respond to the change. The challenge facing the Outer Banks right now is that the natural movement isn’t happening. As people have built roads and homes and jetties and dunes on the islands, the natural movement of sand has stopped. The ocean side has kept eroding but the sound side isn’t growing. It means the Outer Banks are getting narrower and some areas could eventually disappear.

— Frank Graff

Frank Graff is a producer/reporter with UNC-TV, focusing on North Carolina Science Now, a weekly science series that airs Wednesdays, beginning in August 2013, as part of North Carolina Now on UNC-TV. In addition to producing these special segments, Frank will provide additional information related to his stories through this North Carolina Science Now Reporter's Blog!

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