operators of the vessels. In the case of the CURRITUCK, operations ceased 

 when wave heights encountered were in the range of 6 to 8 ft, whereas the 

 ATCHAFALAYA/MERMENTAU operated up to about 10-ft wave heights. Using the 

 results of the wave propagation model calculations, SAW determined limiting 

 wave heights for dredging operations in Oregon Inlet to be deepwater signif- 

 icant wave heights of 3.0 ft for the CURRITUCK and 4.0 ft for the 

 ATCHAFALAYA/MERMENTAU classes. 



105. The wave height limitations for the dredging operations predicted by 

 the wave propagation model were substantiated by SAW which compared the daily 

 logs of the dredge HYDE (which operated at Oregon Inlet during 1960-1971) to 

 wave data recorded during most of this period. The HYDE was a seagoing 

 trailer-suction hopper dredge with seakeeping qualities similar to those of 

 the ATCHAFALAYA/MERMENTAU class dredge. The wave gage was located approxi- 

 mately 8 miles north of Oregon Inlet on a fishing pier at Nags Head. On the 

 basis of the comparison, it was concluded that the HYDE ceased to operate when 

 significant wave heights reached 4.0 ft at the wave gage. 



Single Jetty Evaluation 



106. The sediment transport model developed for transport within the surf 

 zone and beyond was applied to Oregon Inlet for evaluating erosion and accre- 

 tion in the ocean bar entrance channel and the lateral movement of the bar 

 channel for the case in which just the south jetty was in place. This single 

 jetty condition simulates a construction sequence in which construction of the 

 south jetty would be completed prior to the beginning of construction of the 

 north jetty. 



107. The wave climate for an average year at a depth of 60 ft MLW near 

 Oregon Inlet was obtained from WESWIS based on 20-year hindcast data. This 

 information is given in the form of percent of occurrence of wave height, 

 period, and direction combinations. For running the sediment model, the wave 

 climate information was further consolidated into 35 combinations of wave 

 height, period, and direction, and the percent of occurrence of each 

 combination was determined. Table 2 shows the 35 combinations. The wave 

 propagation model was run with the south jetty in place for these combina- 

 tions, and the local wave information at each of the grid cells and the 

 breaker line(s) was determined for each case. This information was used as 



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