— I 1 — 



PROFILE VIEWS 



CONFIGURATION RP-? 



n 



RELATIVE FREEBOARD, F' 



Figure 21. Comparison of overtopping trend curves for the Roughans 

 Point seawall fronted by a standard riprap revetment (configura- 

 tion RP-2) and the same seawall fronted by a wide berm, absorber 

 revetment (configuration RP-4) 



a berm located near the mean water level is effective in disrupting wave 

 action near the seawall and in reducing overtopping rates. This finding is 

 consistent with conclusions reached by Owen (1982b) based on laboratory tests 

 of irregular wave overtopping of sea dikes. 

 Seawall crest height 



27. A fourth method to reduce wave overtopping is to increase the crest 

 elevation of the seawall. Because overtopping rates increase approximately 

 exponentially with freeboard, the value of increasing the height of the wall 

 can be readily appreciated. Tests were conducted during the Roughans Point 

 study using a 1.0-ft cap and a 2.0-ft cap on the seawall. These caps were 

 found to be very effective in reducing overtopping rates. Figure 22 shows 

 overtopping trends for four seawall /revetment configurations, including con- 

 figuration 7 with a 1.0-ft cap and configuration 8 with a 2.0-ft cap. con- 

 figurations 4, 7, and 8 have the same wide berm absorber revetment profile so 

 that the effectiveness of a cap can be easily appreciated in Figure 22 by 



30 



