b. Three-Dimensional Wave Attenuation Tests. 



Based on the two- 



dimensional test results and relative costs of the plans investigated by 

 Carver (1979), it was determined that plan 1, with proper alinement of the 

 structures, could provide adequate and economical protection. Therefore, it 

 was decided to initially test four configurations of plan 1 in the 25-foot 

 depth, and based on the test results, to select two configurations for testing 

 in a 10-foot depth. The 10-foot depth represents low tide conditions at 

 Olympia Harbor. To investigate the combined effects of transmission and 

 diffraction, three modules of plan 1 were used. Tests were conducted with the 

 anchor chains crossed and the breakwater sections arranged in the following 

 configurations: 60° linear, 75° linear, concave, and convex. The layout of 

 the three-dimensional 60° configuration is shown in Figure 25. 



r 



v 



K 



WAVE ABSORBER 



JZ^__ 



WAVE ABSORBER 



00 ISO FT 



• INDICATES WAVE GAGE LOCATION 



MODEL LAYOUT 

 60° LINEAR CONFIGURATION 



Figure 25. Three-dimensional physical model configuration of single-pontoon 

 floating breakwater for potential application at Olympia Harbor, 

 Washington (after Carver, 1979). 



For all configurations, transmittd wave heights were measured directly 

 behind the breakwaters (gages 1, 2, and 3), in the vicinity of the proposed 

 marina (gages 11 and 12), and at selected intermediate locations (gages 4 to 

 10). Transmitted wave heights and coefficients of transmission for the 25- 

 foot depths are presented in Table 1 for two representative sets of condi- 

 tions. It is apparent from these data that no specific configuration yields 

 consistently lower transmitted heights for all test conditions at all gage 

 locations. The model study showed that no adverse motions of the structures 

 were observed for the range of configurations and test conditions. Also, no 

 violent motions of roll, pitch, heave, or sway were observed. The model did 

 not simulate any type of bumper system between individual sections; however, 



57 



