4.4 Effect of Overtopping on Stability 



The effect of wave overtopping on armor stability was investigated by Van 

 der Meer and Daemen (1994). They gave a reduction factor for stable armor size as 



1 



1.25 -4.SRp 



for 0<R;< 0.052 ^^ jq^ 



with 



r:-^ 



:£ ^ = r (4.11) 



//J2u - gr; 



where R^ is the freeboard or structure crest height above the still water level. There is an 

 odd mix of wave height statistics in Equation 4. 1 1 . Substituting the conditions in the 

 experiment discussed herein yields R^* of 0.063 - 0.076 for the toe depth of /i, = 1 1.9 cm 

 and 0.047 - 0.058 for h, = 15.8 cm. Therefore, the 11.9-cm depth is outside the range of 

 applicability of Equations 4.10 and 4.11. Actually, wave overtopping was negligible in 

 the shallow depth of /i, = 1 1.9 cm. For /i, = 15.8 cm, the range of stable armor size 

 reduction coefficients is 0.98 < ^^ ^ lO- Therefore, wave overtopping had negligible 

 effect on stability of the armor layer. 



4.5 Armor Profiler and Profile Measuring Technique 



A structure profiler similar in concept to that used by Davies et al. (1994) 

 was constructed. The profiler design and construction are described in detail in 

 Winkelman (1998), who participated in the planning and setup of the project. 

 The profiler, shown in Figures 4.8 and 4.9, consisted of eight aluminum profiling arms, 



74 



