where d is the water depth at or near the structure toe. The procedure 

 used to calculate the zero-moment wave height at the toe of the structure was 

 to calculate the value by using both linear shoaling and Equation 1 and then 

 taking the average of the two estimates. If the average exceeded the maximum 

 value suggested by Equation 2, then that limiting value was used. 



13. The ability of the above procedure to estimate H^ in shallow 

 water is demonstrated in Figure 7 using wave-tank calibration data collected 



17 

 16 

 15 

 14 





1 1 1 



i 



i i i 



■ muA 



■ 



- 



13 











— 



12 



S 



1 

 I 10 



Q 



— 



PERFECT COR RE LA TION 



■ 



■J" 





- 



K 9 





AND PREDICTION LINE — . 







_ 



a 

 a 



uj 8 

 0C 



a. 



2 7 

 DC 



m K 

 > ° 





^" / " 



■ 



■ 





- 



5 





^f m 









~ 



4 













- 



3 













- 



2 

 1 



n 





i i i 



i 



i i i 



i 



- 



OBSERVED, H mn , CM 



Figure 7. Predicted versus observed H^ for tank calibration data 



prior to a study of wave overtopping of a seawall (Ahrens, Heimbaugh, and 

 Davidson 1986). This calibration data included a wide range of wave periods 

 and an extensive amount of wave shoaling and breaking for many conditions 

 between the offshore wave gages and an inshore gage located in front of a wave 

 absorber beach. For the calibration data shown in Figure 7, the offshore 

 water depth ranged from 61.9 to 66.2 cm; the inshore water depth ranged from 

 22.9 to 27.2 cm; the offshore FL ranged from 1.6 to 21.5 cm; the inshore 

 Hjjjq ranged from 1.5 to 16.4 cm; and the period of peak energy density ranged 

 from 1.75 to 3.00 sec. The hybrid method given above appears to work well for 

 CERC calibration data because linear shoaling tends to overestimate inshore 



10 



