Beach dynamics 



Using a wave tank at the N. C. 

 Marine Resources Center at Ft. 

 Fisher, Sea Grant coastal engineer 

 Spencer Rogers can simulate the 

 workings of the ocean, beach and 

 dunes. The tank, which Rogers 

 designed, gives a cross-sectional 

 view of the ocean-berm system 

 from the dunes to a few hundred 

 feet offshore. By changing the tur- 

 bulence in the tank, Rogers can 

 demonstrate how different wave 

 sizes can affect the beach and 

 dune. For instance, during calm 

 weather when waves are smaller, 

 the beach is wide with a gradual 

 incline toward the dunes. But dur- 

 ing storms, when the waves are 

 larger, the beach is narrow and 

 steep. 



In a small test area near Ft. 

 Fisher , Rogers has anchored 

 several old Christmas trees (left) 

 to rebuild the dunes. 



The National Park Service has 

 adopted just that philosophy in its 

 management of the man-made dunes 

 along its Outer Banks national 

 seashores. The park service has 

 decided to abandon its upkeep of the 

 high, man-made dunes. 



Dunes built with bulldozers and 

 dump trucks are costly. A simpler and 

 less expensive way to build or restore 

 them is to plant salt-resistant grasses. 

 Planted in an area rich in sand-laden 

 winds, beach grasses can collect a 

 natural dune. 



North Carolina State University soil 

 scientist Steve Broome, a Sea Grant 

 researcher, recommends three types of 

 grasses for building dunes in North 

 Carolina — American beachgrass, sea 

 oats and bitter panicum. Why these 

 grasses? They're tough. They can 

 tolerate accumulating sand, wind 

 gusts, salt spray, flooding, drought, 

 the beaming beach sun and a meager 

 food supply. But, they do have one 

 weakness in their armor — they can't 

 withstand being trampled by people 

 and vehicles. 



Beach grasses grow upward with the 

 dune. Sometimes, during a storm, the 

 ocean cuts away a slice of the dune and 

 you can see the extensive network of 

 roots and rhizomes that run through 

 the dunes. 



Broome says it is best to plant a 

 combination of beach grasses. The 

 American beachgrass, which makes a 

 good dune starter, usually only sur- 

 vives a few years. Not native to North 

 Carolina, the American beachgrass 

 must have a constant supply of ac- 

 cumulating sand. It also falls easy 

 prey to insects and disease. Sea oats 

 are hardier. Broome says, but unlike 

 the American beachgrass and bitter 

 panicum. they can't be purchased at a 

 nursery. Sea oats do not grow well un- 

 der nursery conditions and must be 

 dug from existing dunes. It's illegal in 

 North Carolina, however, to dig up sea 

 oats or cut-off their oat-like tassles. 

 But Broome suggests that you find a 

 neighbor who is willing to let you 

 remove a few sea oat plantings or seeds 

 from his or her property. 



If you would like to know more 

 about when, where and how to build or 

 restore dunes, read the Sea Grant 

 publication. The Dune Book , How 

 to Plant Grasses for Dune 

 Stabilization . For a free copy, write 

 UNC Sea Grant, Box 5001, Raleigh, 

 N.C. 27650. Ask for Sea Grant 

 publication, UNC-SG-76-16. 



But grasses aren't the only way to 

 build a dune, just one of the more 

 natural ways, Sea Grant coastal 

 engineer Spencer Rogers says you can 

 build a dune with sand fences, brush 

 pilings and even old Christmas trees. 



Once a dune is planted over with 

 grasses, it's stronger. But no dune is 

 permanent. A ferocious nor'easter or 

 hurricane can erase dunes. "A lot of 

 people along the coast have a false 

 sense of security where the dunes are 

 concerned." Riggs says. "They can't 

 save you every time." 



Caution: ORVs can be hazardous to a dune's health 



So what happens to this thriving 

 community of sand, grasses and 

 wildlife when it's overrun by off-road 

 vehicles (ORVs)? It's in trouble, ac- 

 cording to Sea Grant researcher Paul 

 Hosier of UNC-Wilmington. 



Hosier, who has been studying the 

 effects of ORVs on dunes for almost 

 two years, has found that the same 

 dunes that can hold off a pounding 

 ocean cannot tolerate being trampled 

 by feet and vehicles. 



The first pass or two over the dunes 

 by an ORV kills off the grasses and the 

 sea oats by breaking the stems and ex- 

 posing the roots to the sun, Hosier 

 says. Voiding the dunes of vegetation 

 not only keeps the dunes from grow- 

 ing, but also destroys the "fingers" 

 that hold the dune together. The bare 

 sand is prey to the wind and other 

 vehicles. 



"It takes the wind and the vehicle 

 working together to create a large dune 

 blowout," Hosier says. "When a vehi- 

 cle traverses the dune, the first few 

 passes disrupt the dune and move sand 

 down slope. Following that, the wind 

 removes more sand. The whole process 

 is repeated when the next ORV passes. 

 Before long, there's no dune left." 



"I've seen four and five-foot dunes 

 leveled by ORVs," he adds. "These are 

 dunes that can't be duplicated without 

 a gradual rebuilding process that may 

 take years." 



Leveling the dunes makes a hole in 

 their defense for high tides and strong 

 storms to come sweeping through. 

 "It's like the Dutch boy taking his 

 finger out of the dike," Hosier says. 



Not only is it harmful to drive on 

 the dunes, but it's destructive to drive 

 along the dune base. Driving along the 

 seaward foot of the dune destroys its 

 growing edge by killing the beach grass 

 that collects new sand. Hosier suggests 

 that people who need to drive on the 

 beach should stay on the wet sand area 

 between the low and high tide marks. 

 And, he adds, using designated access 

 ramps --to reach the beach will lessen 

 the impact of ORVs on the dunes. 



Hosier points to the Fort Fisher area 

 in New Hanover County as an exam- 

 ple of what unregulated ORV traffic 

 can do. "There is no law enforcement 

 there and people drive all over the 

 dunes." he says. "The dunes are 

 devastated; there is a 20 percent 

 reduction in the vegetation; and so 



many crossovers have been made per- 

 pendicular to the beach that the next 

 big northeaster or hurricane is going to 

 cause a massive washover." 



Fortunately, there aren't many sites 

 as trampled as Fort Fisher. Many 

 coastal communities have begun 

 regulating ORV traffic. But the 

 regulations have drawn controversy. 

 ORV supporters say the regulations 

 hurt local economies and unfairly limit 

 the fisherman's access to the beach. 

 Opponents say the vehicles damage 

 dunes, plants and animals. 



Hosier points out that ORV use 

 along the North Carolina beaches has 

 increased dramatically over the last 

 ten years. In 1977 alone. 100.000 peo- 

 ple drove the beaches of the Cape Hat- 

 teras National Seashore. 



About 85 percent of the ORV 

 drivers are fishermen. Hosier says. 

 "But fishermen generally cross the 

 dunes at prescribed crossovers, run up 

 and down the beach to fish and then 



come back across the dunes at a 

 crossover." he explains. "That's fine." 

 Hosier thinks it's the people who "bust 

 dunes" for fun that cause the most 

 trouble. "They're why we need dune 

 ordinances." he says. 



Hosier says there are federal, state, 

 county, municipal and private island 

 ordinances in North Carolina that 

 limit dune driving in one way or 

 another. Some ordinances limit the 

 time of year ORV operators can drive 

 on the beach. Still others limit beach 

 access to fishermen and some use a 

 combination of limitations. 



Sea Grant publishes a free 

 pamphlet. Making Tracks, A Guide 

 to Off-Road Driving at the Beach, 

 which lists some of the dune regula- 

 tions for beaches along the coast. The 

 pamphlet also offers other ORV infor- 

 mation. For a free copy, write UNC 

 Sea Grant, Box 5001. Raleigh, N.C. 

 27650. Ask for Sea Grant publication 

 79-06. 



An ORV rides over the crumbling dunes at Ft. Fisher 



