This nearshore predicted significant wave height is lower than if waves 

 were monochromatic. If the SPM monochromatic design breaker height 

 curves (Fig. 7-4 in the SPM) were used with this example, the predicted 

 breakwater height, H£>, would be: 



Hfr = 6.23 feet (1.9 meters) . 



*************** EXAMPLE 2**************** 



GIVEN : Wave conditions were measured as T = 16 seconds and (Hs)i =6.56 

 feet (2.0 meters) where the bottom slope was m = 0.05 (1 on 20) and 

 water depth was dj = 13.1 feet (4.0 meters). 



FIND : The significant wave height at a second location where d 2 = 3.28 

 feet (1.0 meter) . 



SOLUTION : Using method 2, 



(a) (Hsh/di = firf = °* 5 



and 13 1 



di/gT 2 = '- — r5-= 0.0016 . 



1 32. 2 (16) 2 



(b) The abscissa and ordinate values in (a) intersect where 



H^/gT 2 = 0.00048 on Figure 5 



(c) At location (b) , d 2 /gT 2 = — 5j28 — 0.0004 



^ . 32.2(16) 2 



(d) At d 2 /gT 2 = 0.0004 and ILJ/gT 2 = 0.00048, (Hs/d) 2 = 0.83 



(e) Finally, the predicted significant wave height at location (b) is 

 (H s ) 2 = d 2 (H s /d) 2 = 3.28(0.83) = 2.7 feet CO. 83 meter) . 



************************************ 



IV. SUMMARY 



Curves for estimating nearshore significant wave heights for irregular 

 waves using the analytical model of Goda (1975) are presented with exam- 

 ples for use. The standard use of the SPM would result in monochromatic 

 nearshore breaker heights which are larger than the irregular wave sig- 

 nificant heights given in this report. 



