_FIND: The deepwater height H of the waves resulting in the given breaker 

 heights Hj^ 



2 

 SO LUTION ; Calculate H, /gT for each wave condition to be investigated. 



h 2.8 



gl^ (9.8) (6)^ 



= 0.0079 (T = 6 s) 



9 



With the computed value of Hi^/gT enter Figure 7-5 to the curve for a 



slope of m = 0.05 and determine Hr/H' which may be considered an 



ultimate shoaling coefficient or the shoaling coefficient when breaking 

 occurs. 



— X- = 0.0079 ; -^ = 1.16 (T = 6 s) 

 gT^ ^o 



With the value of Hj,/H' thus obtained and with the value of I^ obtained 

 from a refraction analysis, the deepwater wave height resulting in the 

 design breaker may be found with equation (7-6). 



YIq is the actual deepwater wave height, where HT is the wave height in 

 deep water if no refraction occurred (H' = unrefracted deepwater height) . 

 Where the bathmetry is such that significant wave energy is dissipated by 

 bottom friction as the waves travel from deep water to the structure site, 

 the computed deepwater height should be increased accordingly (see Ch. 3, 

 Sec. VII, HURRICANE WAVES, for a discussion of wave height attenuation by 

 bottom friction). 



Applying equation (7-6) to the example problem gives 



«o = (0.85) I1.I6) = 2-8 - (9.2 ft) (T = 6 s) 



A similar analysis for the 10-second wave gives 



l^ = 2.8 m (9.2 ft) (T = 10 s) 



A wave advancing from the direction for which refraction was analyzed, and 

 with a height in deep water greater than the computed I^ , will break at a 

 distance greater than % feet in front of the structure. 



Waves with a deepwater height less than the I^ computed above could break 

 directly against the structure; however, the corresponding breaker height 

 will be less than the design breaker height determined from Figure 7-4. 



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7-13 



