PART IV: DISCUSSION 



20. It was found that a standard riprap revetment (Configuration 2) in 

 front of the seawall (Figures 6 and 7 and Plate 2) reduced wave overtopping 

 rates in the range of 40 to 50 percent over what was expected to overtop in 

 the absence of the revetment (Configuration 1, Plate 1). A comparison of the 

 data trends for Configuration 1 and 2 is given in Figure 8. In general, the 

 standard revetment did not reduce overtopping rates very effectively. Two 

 problems, which were not detected prior to the test, can be identified with 

 the standard revetment: 



a. If the top of the revetment is too high, it interferes with the 

 recurve causing the recurve not to function effectively. 



b. If the revetment acts as a ramp, which it often does, it causes 

 the waves to ride up and over the wall without a major disconti- 

 nuity in the flow. This "ramp effect" is pictured in Figure 9. 



21. The wave absorber revetment (Configuration 3, Table 1, and Fig- 

 ure 10) was an attempt to make the revetment a better wave absorber by adding 

 armor stone. Configuration 3's performance (Plate 3) was poor because it was 

 not recognized at that point how important it was to maintain discontinuities 

 in the configuration, such as the recurve and the wall itself, to disrupt the 

 wave action and runup flow. In designing Configuration 3, the main goal was 

 to try to dissipate as much wave energy as possible within the spatial 

 constraints. 



22. The revetment with a wide berm at +8 ft NGVD (Configuration 4, 

 Table 1, and Figure 11) was designed to provide a discontinuity to wave action 

 and runup flow, to allow the recurve to function effectively, and to still be 

 a good dissipator of wave energy. Configuration 4 results (Plate 4) show it 

 to be a very effective design in reducing overtopping, and its performance is 

 better compared to the standard revetment (Configuration 2 in Figure 12). 



23. Configuration 5 (Table 1 and Figure 13), with a double berm, was an 

 attempt to fine tune the idea developed in Configuration 4. The slope con- 

 necting the two berms was 1V on 2H and was not stable with the more severe 

 wave conditions. As a consequence, the two berms had merged into a single, 

 somewhat sloped, berm by the end of the tests. Configuration 5's performance 

 (Plate 5) indicates it was effective in terms of reducing overtopping, but the 

 need for two berms is probably not worth the added design and construction 

 complexity. A single rather flat slope between +6 and +10 ft NGVD probably 



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