where Rp is the wave runup associated with, a particular probability of 

 exceedance, p; Rg is th.e wave runup with, a given deepwater significant 

 height and period; and K^ is the ratio of Rp to Rg; the index "i" is 

 employed for use in computations shown below. Rg is referred to as the 

 significant runup and is predicted in the conventional manner based on 

 laboratory tests using monochromatic waves as shown in the SPM, Equation 

 (2) provides the transition between monochromatic and irregular conditions, 



2. Equation (1) can now be rewritten as 



[gOSCHo^l] 



1/2 



0.217 



tanh' 



(3) 



where Q,^ is the overtopping rate associated with a particular value of 

 K^, and (.%) g is the equivalent deepwater significant wave height. 

 (H^)g has replaced H^ in equation (3) to emphasize the distinction be- 

 tween this equation and the monochromatic overtopping equation (eq. 1), 

 and denotes that it is the significant height which is being used in this 



The term (h 



ds^R. 



will be referred to as the relative free- 



procedure, 

 board. 



3. The average overtopping rate for runups with a Rayleigh distribu- 

 tion, Qy,, was computed by equation (3) using the following relation: 



for 



199 



*■ ■ ife E ''^ 



i=l 



p = 0.005 X i, i = 1, 2, 3 



199 . 



C4) 



The index "i" causes a range of probabilities to be generated; these 

 probabilities when substituted into equation (2) generate a range of 

 values of the parameter K-. K-, in turn, is substituted into equation 

 (3) to generate the Q-^^'s. The 199 values of overtopping are computed 

 for a fixed value of the relative freeboard corresponding to the various 

 values of K^ which are generated by varying the probability of exceed- 

 ance, p, from 0,005 to 0.99S in increments of 0.005. The average value 

 of the Q-z^'s (eq. 4) represents the average rate of overtopping expected 

 for a time interval of 199 waves. 



4. Using the procedure shown in steps 2 and 3 above, the largest 

 value of Q^ corresponds to a value of p = 0.005. Since the peak rates 

 of overtopping might be of concern in some design situations, the follow- 

 ing definition is useful: 



iQ.5 



Q^ associated with a probability of exceedance 

 of p = 0.005 or 0.5 percent . 



