the offshore structure with the larger discharges moving the sediment fur- 

 ther seaward. For 15-sec, 14-ft test waves from west (Photos 79-82), mate- 

 rial moved into a counterclockwise eddy once in the cove, and larger 

 discharges resulted in sediment movement and subsequent deposits more 

 northerly in the vicinity of the seaward head of the offshore breakwater. 



Wave-induced sediment tracer patterns and subsequent deposits for ex- 

 isting conditions are shown in Photos 83-86 for test waves from northwest 

 and southwest. For waves from northwest, material generally moved into 

 the cove and deposited in a clockwise eddy in the northern portion of the 

 cove. Test waves from southwest resulted in material migrating into the 

 cove and generally depositing in a counterclockwise eddy. Northwest 

 waves moved the material further toward the center of the cove than did 

 wave conditions from southwest. 



Results of wave-induced sediment tracer tests for the offshore breakwa- 

 ter plan are presented in Photos 87-90 for test waves from northwest and 

 southwest. For test waves from northwest, tracer material moved into the 

 cove and deposited in a clockwise eddy in the northern portion similar to 

 existing conditions. For waves from southwest, some sediment material 

 migrated into the cove between the breakwater and the shoreline, and 

 some deposited seaward of the breakwater in a counterclockwise eddy. 



Discussion of sediment tracer tests 



A comparison of riverine sediment tracer patterns for existing condi- 

 tions and the offshore breakwater plan with no waves indicates that the 

 patterns are similar, with the exception of the 100-year (41,000 cfs) dis- 

 charge. The breakwater prevented the material from moving as far sea- 

 ward in the cove as it did under existing conditions. 



A comparison of riverine sediment tracer patterns for the offshore 

 breakwater plan with wave conditions from west-northwest and west indi- 

 cates that the breakwater slightly changes the paths of migration and sub- 

 sequent deposits for some river discharges and does not for others. For 

 13-sec, 14-ft test waves from west-northwest, tracer material moved fur- 

 ther seaward into the cove without the breakwater in place, in particular 

 for the 20,000- and 27,000-cfs discharges. The higher discharges (33,000 

 and 41,000 cfs) resulted in similar patterns for existing conditions and the 

 breakwater plan for these wave conditions. For 13-sec, 14-ft waves from 

 west, sediment moved straight out of the river into the cove with the break- 

 water installed for the various discharges. Without the structure in place, 

 material migrated more northerly after entering the cove. Successively 

 larger discharges also resulted in material moving in a slightly more north- 

 erly path than it did with the structure installed. For 15-sec, 20-ft test 

 waves from west-northwest, sediment tracer patterns in the cove were sim- 

 ilar for the various discharges both with and without the offshore struc- 

 ture. These wave conditions from west resulted in material migrating 

 slightly further seaward for the 27,000- to 41,000-cfs discharges with the 



24 



Chapter 4 Tests and Results 



