The average values of wave heights in the entrance for all operational 

 wave conditions and all five directions are 6.2 ft for existing conditions 

 and 4.5 ft for the offshore breakwater plan. These data indicate that the 

 magnitude of the average wave height in the jettied entrance is decreased 

 by about 27 percent as a result of the offshore breakwater. 



Sediment tracer tests 



Riverine sediment tracer patterns for existing conditions are shown in 

 Photos 41-45 for river discharges ranging from 7,000 to 41,000 cfs with 

 no waves. The 2-year discharge (7,000 cfs) barely moved the tracer mate- 

 rial, but each successively larger flow resulted in tracer deposits further 

 seaward in Noyo Cove. 



Sediment tracer patterns from the river with the offshore breakwater in- 

 stalled are shown in Photos 46-50 for river discharges ranging from 7,000 

 to 41,000 cfs with no waves. Again, the 7,000-cfs discharge hardly 

 moved the tracer material out of the river mouth, but successively larger 

 discharges moved the material further seaward in the cove. The offshore 

 breakwater prevented the maximum (41,000 cfs) discharge from moving 

 the tracer material as far seaward as it moved under existing conditions. 



Riverine sediment tracer patterns for existing conditions are shown in 

 Photos 51-66 for river discharges ranging from 20,000 to 41,000 cfs with 

 13-sec, 14-ft and 15-sec, 20-ft waves from west-northwest and west. For 

 waves from west-northwest (Photos 51-58), sediment tracer migrated sea- 

 ward from the river entrance. Instead of moving directly down the axis of 

 the channel, the material moved slightly northerly as it entered the cove. 

 Successively larger discharges resulted in the material moving further sea- 

 ward and into a counterclockwise eddy in the cove. For 13-sec, 14-ft test 

 waves from west (Photos 59-62), riverine sediment patterns were similar 

 to the west-northwest patterns. After clearing the jetties, material moved 

 northerly, and larger discharges resulted in seaward migration of the mate- 

 rial in a counterclockwise eddy. For 15-sec, 20-ft test waves (Photos 63- 

 66), however, material entering the cove moved slightly south of the 

 jettied entrance and then into a clockwise eddy. The material did not 

 move as far seaward in the cove for the larger discharges as it had done in 

 previous tests. 



Sediment tracer patterns from the river with the offshore breakwater 

 plan installed are presented in Photos 67-82 for 20,000- to 41,000-cfs 

 river discharges with 13-sec, 14-ft and 15-sec, 20-ft test waves from west- 

 northwest and west. For test waves from west-northwest (Photos 67-74), 

 riverine sediment moved into a counterclockwise eddy immediately out- 

 side the jettied entrance for the 20,000-cfs discharge. Successively larger 

 discharges resulted in the material moving in a slightly northerly path to- 

 ward the seaward head of the offshore breakwater. Larger discharges re- 

 sulted in more seaward deposits. For 13-sec, 14-ft test waves from west 

 (Photos 75-78), material migrated from the entrance toward the head of 



Chapter 4 Tests and Results 



23 



