CLOCKWISE FROM BOTTOM LEFT: This is an example of an on-grade walkway with railings. David Nash 

 developed a float germination system for dune plants at Oak Island. Tina Pritchard was involved in the 

 Oak Island dune project. A dune is covered with American beachgrass. New dunes form around sea oats. 



DUNE 

 FEATURES 



Ocean sand 

 dunes are geologic 

 features that are in 

 a constant state of 

 change — some- 

 where between 

 building in elevation 

 with wind-trapped 

 sand and getting flat- 

 tened in an extreme 

 storm or hurricane. 

 Dunes are defined as an area landward of the active beach where 

 dune grasses are dominant plants. It might be a classic dune shape that rises 

 40 feet in height and is covered with sea oats, a recent overwash terrace 

 flattened by a hurricane where the buried sand grasses have yet to pop up 

 through the new sand, or anywhere in between. 



In addition to their aesthetic benefits, sand dunes and dune vegetation 

 can provide substantial protection from storm-induced erosion. The larger 

 the dune, the more time it takes to be eroded by the waves, and the more 

 protection it provides to areas further landward. 



If the dunes are large enough, the waves and storm surge are pre- 

 vented from washing across the barrier island. Flooding may occur from 

 the backside of the island but not directly from the ocean. "Even if the dune 

 is breached and the shoreline is overwashed, the sand stored in the dunes 

 and eroded by the storm reduces the incoming wave heights compared to 

 areas without dunes," says Rogers. 



For these reasons, protecting the existing dunes and building larger 

 dunes with dune vegetation are useful shoreline management practices. 



"Remember that erosion has many causes," says Rogers. "Determine 

 what is causing your erosion before planting or building dunes." 



Areas subject to seasonal fluctuations are never good places for new 

 dunes. In areas experiencing long-term or inlet erosion, planting vegetation 

 or installing sand fencing is seldom recommended. 



"Dune-building efforts should concentrate on areas well landward of 

 the prestorm vegetation system," says Rogers. "If you start too close to the 

 water, you may lose your storm protection to chronic erosion before the 

 big storm hits. However, if you have recently had a direct hit by a major 

 hurricane and lost 50 to 100 feet of dune, you are likely to have a wide, 

 recovering area on which to work." 



Faced with recent dune erosion, most people have a strong desire to 

 return the dune to its previous location. 



"However, that can be a mistake," says Nash. "The two most common 

 errors when building dunes are trying to stop long-term erosion and starting 

 the dune too far seaward. If you avoid these mistakes, you will end up with a 

 better dune. It is better to build a dune as far landward as possible." 



DUNE VEGETATION 



Only a few species of plants can adapt to the dunes closest to the ocean 

 and beach — where there are high levels of salt spray, continuous wind, large 

 amounts of wind-blown sand and other environmental factors. 



Coastal dune plants must be able to survive in soils that are low in nu- 

 trients and moisture and have extreme fluctuations in temperature and ocean 

 overwash. The vegetation aids in forming the dune and plays an important 

 role in the coastal dune ecosystem. 



"Dune vegetation is nature's way to build and stabilize sand dunes," 

 says Nash. "Plants provide food and habitat for animals and birds while add- 

 ing beauty to the coastal environment. Planting and protecting dune vegeta- 

 tion is one of the easiest and most important things we can do to conserve this 

 valuable coastal resource." 



The typical vegetation zones from the ocean to the sound are: pioneer 

 dune plants, grassland species, shrub thicket and maritime forest 



Climate is the primary factor limiting the geographic range of pioneer 

 zone coastal plants species. Along the mid- Atlantic coast, the dunes between 

 the Chesapeake Bay and Cape Lookout are the approximate transition zone 

 for several species. 



For example, sea oats prefer the warmer climate found south of this area 

 and appear to be limited in their northern range by cold temperatures. 



American beachgrass is the dominant pioneer zone species north of the 

 transition zone, tending to die back when stressed by the hot, dry conditions 

 found farther south. Both American beachgrass and sea oats are excellent 

 sand trappers and dune stabilizers. 



Since local plants take years to evolve, they are usually best adapted 

 to the climate where they were first grown. For example, South Florida sea 

 oats do not adapt as well in the cooler climate of North Carolina as they do 

 in Florida and American beachgrass from New Jersey is not well suited to 

 North Carolina's warmer climate. 



"Therefore, it is always best to obtain dune plants from seeds or parent 

 material originating as close as possible to the beach where they are planted," 

 says Nash. "When possible, acquire seedlings or transplants that were grown 

 from seeds or cuttings originating within a 100-mile radius of your beach." 



18 WINTER 2004 



