0.42 0.46 



RELATIVE FREEBOARD. F' 



Figure 14. Comparison of overtopping trend curves for the 



three Cape Hatteras seawall/revetment configurations (CH-1, 



CH-2, and CH-3) 



Cape Hatteras seawall provides an illustration of the effectiveness of toe 

 protection rubble in reducing overtopping of the wall. Figure 19 shows over- 

 topping data for the Cape Hatteras profile with a vertical wall. A number of 

 the data points fall conspicuously below the overtopping trend established by 

 regression analysis. Analysis of the data indicates that these points are all 

 associated with the lowest water level tested. Since the dimensionless free- 

 board defined by Equation 1 takes the water level into consideration, data 

 collected at all water levels should all follow the same trend in figures like 

 Figure 19 unless there is a strong influence from another factor. Additional 

 analysis indicates that when there is relatively shallow water over the rubble 

 toe protection the rubble is quite effective in dissipating wave energy and 

 reducing wave overtopping even when the wall is vertical. However, there 

 appears to be a point when a small increase in water depth will make the toe 

 protection rubble much less effective in reducing overtopping. This effect is 

 demonstrated in Figure 19 where the data collected at the lowest water level 



25 



