would have been just as effective as the double berm. Problems with armor 

 stability would not have been encountered, and construction would be easier. 



24. Configurations 6, 7, and 8 (Table 1 and Figures 14, 15, and 16) use 

 a combination of fronting revetment and a cap on the seawall in an effort to 

 further reduce overtopping rates. Data plots of Q versus F' for each of 

 these configurations are given in Plates 6, 7, and 8, respectively. Since all 

 the data trends indicate that there is an approximately exponential relation 

 between the freeboard and overtopping rates, adding a cap (vertical height) to 

 the seawall would be an effective means of reducing wave overtopping. Fig- 

 ure 17 shows a comparison of data trends for Configurations 1, 4, 7, and 8 in 

 which Configuration 1 is a seawall with no revetment and Configurations 4, 7, 

 and 8 represent a revetment having a wide berra at +8 ft NGVD and a seawall 

 with no cap, a 1.0-ft cap, and a 2.0-ft cap, respectively. These data show 

 that a wide berm revetment (Configuration 4) is better than no revetment 

 (Configuration 1), but Configuration 4 can be made more effective by adding 

 height to the wall (Configurations 7 and 8). One way to think about the 

 effectiveness of added wall height is to consider the amount of stone that 

 would have to be placed in front of the seawall to obtain a similar amount of 

 reduction in overtopping as a 1.0-foot cap on the seawall. Although Figure 17 

 does not answer this question quantitatively, it suggests that a 1.0-ft cap is 

 equivalent to a significant amount of stone in front of the seawall. The co- 

 efficients given in Table 1 and the curves drawn using the coefficients were 

 computed using a seawall crest height of 17.6 ft NGVD in all cases. This ap- 

 proach is rather like treating the cap as just additional stone to dissipate 

 wave energy and is necessary to compare the effectiveness of various configu- 

 rations with various seawall crest elevations. In principle, the performance 

 of a cap (added wall height) can be anticipated using Equations 1 and 2 and 

 test data for a configuration without a cap, but this approach was not tried 

 because of lack of confidence in the ability to extrapolate results using such 

 a new method of predicting overtopping rates. 



25. Configuration 9 (Table 1 and Figure 18) is an attempt to evaluate 

 the ability of an offshore breakwater to reduce wave overtopping without going 

 very far offshore. Since the breakwater was so close to the seawall, it is 

 referred to as a beach breakwater in Table 1 . The beach breakwater was rela- 

 tively effective at reducing overtopping (Plate 9) but even so, its per- 

 formance seemed to be something of a disappointment. The appearance of the 



24 



