Nearshore changes, particularly during storm conditions, can be large. 

 Weekly soundings along both sides of the pier have been collected since July 

 1977. The profile envelope of surveys from July 1976 to December 1979 for the 

 south side of the pier is shown in Figure 40. The maximum sand level change 

 was 4.3 meters measured at 175 meters out; a 1.5-meter change was measured at 

 the end of FRF. 



ie 



^ s 



ffi 



1-5 



-10 



208 400 



DISTANCE FROM BASE LINE CM3 



600 



Figure 40. Profile envelope of soundings taken along 

 the south side of the FRF pier from July 

 1976 to December 1979. 



Birkemeier (1979b) reported that during a storm which produced maximum 

 significant wave heights of 3.8 meters (12.5 feet), 234.3 cubic meters per 

 meter (93.4 cubic yards per foot) eroded along the length of the pier. The 

 storm also produced a relatively flat 200-meter-long terrace at a depth of -6 

 meters (-19.5 feet). 



The localized scour around the pier piles and the concrete abrasion col- 

 lars was investigated by DeWall and Christenson (1979). A maximum scour depth 

 of 1 meter below the surrounding bottom was measured. The laaximum width of 

 holes was 7.3 meters (24 feet). Maximum pile scour was found at 243.8 meters 

 (800 feet) along the pier relative to the base line. 



6. Longshore Bars. 



Lester (1980) examined the frequency and movement of longshore bars, using 

 aerial photos from five overflights, and found that two different bar patterns 

 existed. From Duck north 75 kilometers to Cape Henry, there was a single, 

 uninterrupted bar. However, from Duck south to Oregon Inlet there was a 

 sequence of seven sandbars. These bars had a trisectional formation, in that 

 each bar tended to propagate at an angle from the shore, then continued south- 

 ward parallel to shore for a considerable distance until only remanent indi- 

 cations of the bar remained. The trisectional bar formation is defined as 



67 



