WANCHESE, N.C. (AP) — Sand on some Outer Banks beaches squeezes between the toes better than others.
The beaches may look similar, but sand composition and color changes from location to location, dune to surf and winter to summer.
Ever wonder why? Wave energy, slope of the shoreline and sand source determine the beach make-up, said Reide Corbett, an oceanographer with the University of North Carolina Coastal Studies Institute in Wanchese and professor at East Carolina University.
Heavier grains lie near the breakers while wind-blown, fine grains settle close to dunes. Sand tends to be more coarse in the winter when storms drive greater wave action, he said. Grains are much finer in Wilmington, where wave energy is not as powerful as it is on the Outer Banks, he said.
“You have a lot of variability,” Corbett said. “If you go from Duck to South Nags Head you’re going to see a difference.”
It adds a tricky element to the frequent beach nourishment projects along the Outer Banks. Four in Dare County communities totaling 11 miles are in the works for next year, as communities try to keep storm surge from wrecking homes and roads.
Shorelines at Nags Head and Rodanthe have already been widened.
In every case, engineers scan miles of sea bottom and take dozens of core samples to find a borrow pit that closely matches the beach sand at each place. State permitting agencies check it out. The system works better than past projects, where trucked-in sand that didn’t match the beach didn’t last as long.
Grain sizes vary from smaller than a pin head to tiny rocks with bits of shell.
Larger grain size helps the beach last longer, said Haiqing Liu Kaczkowski, principal engineer for Coastal Science and Engineering of South Carolina. The Nags Head beach five years after a nourishment project has endured better than expected, she said. There have not been devastating storms and the grain size is larger.
“Nags Head has some of the best sand in the state,” she said.
Kaczkowski was the lead engineer on the 10-mile, $36 million Nags Head project in 2011, and is now leading the Buxton job. Widening three miles of Buxton beach begins next year for $25 million.
Costs vary according to the size of the project, the contractor’s bid and distance of the borrow pit from the beach, said a National Park Service report for the Buxton project.
Buxton beach will have a finer grain size and lies in an area with powerful currents and big waves, Kaczkowski said. Buxton sits close to the chin of the Outer Banks that juts eastward and is a target for hurricanes. Will the new sand last?
“There is no guarantee,” she said.
Two years ago, the North Carolina Department of Transportation with the Army Corps of Engineers led a project to widen the two-mile Rodanthe Beach for $20.3 million. The work was done to protect North Carolina 12 from ocean overwash. Each day that North Carolina 12 is closed has an economic impact of $500,000 to $1 million, the National Park Service report said.
Plans are to nourish a total of 8 miles of beaches in Duck, Kitty Hawk and Kill Devil Hills next year at a total cost of $41.7 million. North Carolina 12 has repeatedly washed out at the intersection of Kitty Hawk Road and Virginia Dare Trail.
Tons of tiny grains of sand could make the difference.
Information from: The Virginian-Pilot, http://pilotonline.com