d/H c 



ROUGH SLOPES 



«•- OWE N 



J I I I L 



■+-SPM 



1 



d/H c 



SMOOTH SLOPES 



L^ZTJ 



J L-I 



6 5 4 3 2 1 



STRUCTURE SLOPE 

 (COTANGENT) 



■!-*- 



l^J 



VERTICAL 

 WALL 



Figure 14. General regions of applicability 

 of overtopping methods 



compared. For smooth, steeply sloped structures the SPM method and Owen's 

 method can be compared. 



Comparison of Results 



Goda and SPM — vertical walls 



51. The SPM and Goda methods for vertical seawalls are compared in 

 dimensionless form in Figure 15. The four d /H ratios correspond to the 

 situations tested by Saville. The vertical spread of the SPM method is the 

 effect of the variability of peak wave period, which Goda ignores. The SPM 

 values shown in Figure 15 correspond to the range of wave steepnesses covered 

 by the Q* - a points in SPM Figure 7-24. This approach will also be used to 

 compare the SPM method with Battjes' and Owen's methods. Figure 15 clearly 

 shows the rapid decrease in overtopping with increasing structure height. 



52. The relationship between SPM and Goda estimates is dependent on 

 relative depth d s /(H s ) 



For d_/(H_) =3 and 1.5 , the SPM method 

 s s 



estimates more overtopping than Goda's method. For d/(H s ) = 0.75 , the two 



methods yield comparable estimates. In very shallow water, d /(H ) = 0.4 , 



Goda's method estimates more overtopping than the SPM. This dependence on 



d_/(H a ) implies a dependence on wave breaking and appears to be a result of 

 s s Q 



the different approaches used to extrapolate monochromatic-wave overtopping 

 results to irregular waves. 



28 



