each of a specified depth. A requirement of the model is that depth must 

 increase in the offshore direction. Therefore, the dumps placed in the DOI 

 dredging plan were represented as a flat area of the bathymetry. To simulate 

 the placement of dumped material at a depth of 11 ft, material was placed 

 between the 7- and 11- ft contours. Material was placed also between the 

 11- and 14-ft contours. 



99. The COER model predicted that between 15 and 35 percent of the mate- 

 rial added between the 7- and 11-ft contours, and between 5 and 25 percent of 

 the material added between the 11- and 14-ft contours would be dispersed into 

 the nearshore transport system during the first year. These percentages of 

 material that would move ashore during the first year are similar to those 

 calculated by the model described in this report. Quantitative comparisons 

 between the models are not possible since the COER model cannot simulate the 

 actual bathymetry of the dumping plan. 



Wave-Current Interaction 



100. For cases with and without the jetties, SAW performed an ocean bar 

 channel dredging analysis. A needed input to the analysis was the period of 

 time that split-hull hopper dredges of the CURRITUCK and ATCHAFALAYA/MERMENTAU 

 classes could operate in the channel under the influence of waves. Waves tend 

 to be large near the ocean bar channel as a result of shoaling and refraction 

 on the ocean bar and wave-current interactions. The wave climate at Oregon 

 Inlet was known offshore at a water depth of 60 ft from WESWIS. The wave 

 propagation model described in Part II was used to transform the wave climate 

 at a water depth of 60 ft to the ocean bar channel (including the effects of 

 wave-current interaction) . 



101. The wave propagation model was applied to Oregon Inlet using wave 

 periods of 7, 9, and 12 sec, wave heights of 1 to 6 ft in 1-ft intervals, and 

 the numerical grid shown in Figure 2. Tidal currents were obtained by using 

 the tidal circulation numerical model described in Part II. Jetty spacings of 

 2,500, 3,500, and 5,000 ft and existing conditions without jetties were 

 considered. 



102. Figures 35-37 show some typical results produced by the wave propa- 

 gation model. For example, Figure 35 shows the effect of ebb current magni- 

 tude on wave amplification for a 12-sec wave with an incident wave height of 



76 



