except for very low relative freeboards. The difference between the diraen- 

 sionless estimates is greatest for small amounts of overtopping. The effect 

 of slope cannot be checked because Saville did not test other mild slopes. 

 Owen and SPM — steep slopes 



55. Figure 14 shows that Owen's method can be compared with the SPM 

 method. Figures 7-25, 7-26, and 7-28 of the SPM (1984) present Q* - a 

 values for 1:1.5 and 1:3 smooth slopes and 1:1.5 rough slopes. The range of 

 wave steepnesses and relative water depths tested by Owen limits the compar- 

 ison to a few Q* - a points in the SPM figures. The comparison for 1:3 

 smooth slopes is made in Figure 17 by plotting dimensionless overtopping 

 versus dimensionless freeboard, as in Figures 15 and 16. 



56. Owen's method estimates more overtopping than the SPM method. As 

 the dimensionless freeboard increases and the overtopping decreases, the two 

 estimates diverge. In other words, the difference between the two methods is 

 greatest for very small amounts of overtopping. Similar results are found for 

 both rough and smooth 1:1.5 slopes. 



2 3 1 



DIMENSIONLESS FREEBOARD - F/H c 



Figure 17. Comparison of Owen and SPM methods for esti- 

 mating overtopping of a 1:3 smooth-slope structure 



31 



