Miller (1980) examined the duration of storms using measurements from the 

 CERC Nags Head wave gage. He defined a storm as an event which caused the 

 measured wave height to exceed a critical height equal to the sum of the 

 annual mean significant wave height (0.88 meter) and one standard deviation 

 (0.49 meter). This definition was used to compute Figure 24 which indicates 

 35 percent of all storms were of 1-day duration or longer while only 1 percent 

 exceeded 6.8 days. 



20 30 40 50 60 70 80 



Probobility 



99.99 



Figure 24. Storm duration probability based on wave data recorded 

 by the CERC gage at Nags Head, North Carolina. 



5. Sediment Transport. 



The net longshore transport direction along the northern Outer Banks has 

 been reported as toward both the north (Langfelder, Stafford, and Amein, 1968) 

 and the south (Goldsmith, Sturm, and Thomas, 1977). Jarrett (1978) determined 

 a net southerly transport along the beaches north of Oregon Inlet. 



Although a detailed sediment budget has not been prepared for the FRF 

 area, the longshore sediment transport rates can be estimated based on the 

 visual observations of wave height and direction given in Section IV, 2. 



Average monthly and annual predicted transport rates based on the method 

 recommended in the Shore Protection Manual (SPM) (U.S. Army, Corps of Engi- 

 neers, Coastal Engineering Research Center, 1977) are given in Table 8. Note 

 that the values use a dimensionless proportionality constant, k, equal to 

 one. Generally accepted values of this constant are given at the end of the 

 table. Annual and seasonal variations in net transport, based on the propor- 

 tionality constant, are shown in Figure 25. 



49 



