disposal plan carried out by COER for SAW, using an n-line model, produced 

 similar results. 



127. In order to perform an ocean bar channel dredging analysis, SAW 

 needed to know the period of time that dredges of the CURRITUCK and 

 ATCHAFALAYA/MERMENTAU classes could operate in the entrance channel under the 

 influence of waves. To study this problem, the wave propagation model was 

 run, allowing for wave-current interactions. The tidal currents were calcu- 

 lated by the numerical tide model. The effects of jetty spacing on wave 

 height and steepness were studied for a variety of typical wave conditions. 

 Using these results, SAW determined the limiting wave heights for dredging 

 operations in Oregon Inlet to be deepwater significant heights of 3.0 ft for 

 the CURRITUCK and 4.0 ft for the ATCHAFALAYA/MERMENTAU classes. This was con- 

 firmed by SAW on review of the daily logs of the dredge HYDE which operated at 

 Oregon Inlet. 



128. The modeling system was used to study the erosion and accretion in 

 the entrance channel, as well as the lateral movement of the channel in the 

 presence of the south jetty alone, to simulate a construction sequence in 

 which the south jetty was built before the north jetty. For this purpose, an 

 average year's wave climate obtained from WESWIS was modeled. The wave pro- 

 pagation, wave-induced current, and longshore sediment transport models were 

 run in succession. Also, information on tidal currents and elevations for the 

 mean tide condition obtained from the numerical tide model were used. The 

 sediment transport model simulated an average year, using a time-step of 1 hr . 

 Computer plots showing contours and zones of erosion and accretion were made 

 at intervals of 3 months. 



129. The results of the 1-year simulation showed that a total of 

 1,055,990 cu yd of materials was trapped in the entrance channel during the 

 12-month period, whereas 660,000 cu yd of materials were eroded between the 

 southern boundary of the channel and the south jetty. 



130. On the basis of flow cross sections taken at various locations along 

 the channel at the beginning and end of the numerical simulation, it was 

 determined that the entrance channel could move on the average about 150 ft/yr 

 toward the south jetty. 



90 



