Cod and Ocracoke Island appear to be comparable dune-building environments. 

 Growth rates observed in the Padre Island and Clatsop Plains studies were 

 somewhat higher. Dune growth rates are likely to be greatly influenced by the 

 broadness of the beach as a source of sand and the direction and severity of 

 local winds. 



Table 11. Comparison of annual sand accumulation 

 and dune growth rates in Massachusetts , 

 North Carolina, Texas, and Oregon. 



Location 



Crest growth 

 (m) 



Sand accumulation 

 (mVm) 



Nauset Beach, ^ 

 Cape Cod, Mass. 



0.25 



8.3 



Ocracoke Island, N.C. 



2 

 0.18 



3 



8.4 



1* 

 ?adre Island, Tex. 



0.46 

 0.60 



10.8 



5 

 Clatsop Plains, Oreg. 



0.27 



13.7 



^Average of American beachgrass plots 1, 3, and 5 in 

 Table 9 (7 years growth). 



^Woodhouse, Seneca, and Broome (1976) (10 years 

 growth) . 



^Table 1, sections 12, 13, 14, and 16 in Savage and 

 Woodhouse (1968) (3 years growth) . 



•♦Dahl, ec al. (1975). 



^Meyer and Chester (1977) (30 years growth). 



Savage and Woodhouse (1968) calculated the volume of sand accumulated in 

 four lifts of sand fence over a period of 5 years and 8 months. Annual accu- 

 mulation during this period averaged 6.6 cubic meters per meter. The four 

 lifts of straight fencing at Nauset Beach trapped 9.0 meters per meter per 

 year over a comparable period. 



VI. CONCLUSIONS 



1 . American Beachgrass. 



a. American beachgrass was found to be effective for building dunes and 

 stabilizing sand on Cape Cod. 



b. American beachgrass spreads laterally at rates up to 4.9 meters per 

 year. Previous studies in North Carolina reported spreading rates from 2.4 to 

 3.0 meters per year. Lateral spread was greater in the direction of prevail- 

 ing winds. Prevailing winds are from the west on Cape Cod during the growing 

 season. 



c. American beachgrass is capable of surviving when buried to a depth of 

 0.3 meter by washover deposits. Beachgrass is also tolerant to saltwater in- 

 undation while dormant. 



32 



