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| 20. ABSTRACT (Continued) . 



system of numerical models called Coastal and Inlet Processes (CIP) Numerical 

 Modeling System was developed. It included models for wave propagation, wave- 

 induced currents and setup, sediment transport within and beyond the surf zone, 

 and profile response (onshore-offshore transport). Results from a separate 

 study on numerical simulation of tides and storm surge for Oregon Inlet were 

 utilized in the present investigation. 



As a test for an extreme event, the Ash Wednesday storm of March 1962 was 

 simulated with the profile response model. There was good agreement between the 

 calculated erosion amounts of the shore-normal profiles for Bodie and Pea 

 Islands (on either side of Oregon Inlet) and values measured in the field. 



As an alternative to the stabilization of the entrance channel by con- 

 struction of two jetties, a nonstructural solution proposed by the Department of 

 the Interior was evaluated using the profile response model. The solution 

 involved disposal of the dredged material from the entrance channel in the near- 

 shore region with the idea that the material would be dispersed shoreward by 

 wave action at a rate sufficient to prevent dredging-induced beach erosion. The 

 results of the model indicated that on the average only 25 percent of the 

 disposed material migrated toward the shore in a year. This migration was 

 insufficient to prevent dredging-induced beach erosion. 



In order to perform an ocean bar channel dredging analysis, the US Army 

 Engineer District, Wilmington (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. Using the 

 model results, SAW determined the limiting wave heights for dredging operations 

 to be deepwater significant heights of 3.0 and 4.0 ft, respectively, for the two 

 classes of dredges. 



The CIP 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, simulating a construction sequence in which the south jetty 

 was built before the north jetty. To accomplish this the longshore sediment 

 transport model simulated an average year's wave climate and tide, using the 

 results of the wave, wave-induced current, and tide models. The results of the 

 simulation showed that during the year a total of 1,055,990 cu yd of material 

 was trapped in the entrance channel, whereas a total of 660,000 cu yd of 

 material was eroded between the southern boundary of the channel and the south 

 jetty. It was determined that the entrance channel could move on the average 

 about 150 ft per year toward the south jetty. 



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