for u = the Poisson parameter or the mean number of storm events per year. 

 The slope 3p for the Extremal Type I is approximately 



3r=1-03 (20) 



for all values of R from 20 to 100. 



17. The error due to the hindcast model can also be included in the 

 reliability analysis. The WIS hindcast model when compared to measured data 

 shows at most a difference of about 0.04 for percent occurrence of signifi- 

 cant wave heights larger than 6 m (Figure 11, Corson and Resio 1981). If 

 this value is assumed to be the error in estimating F(x) due to the hind- 

 cast model then a„ from Equation 14 becomes 



o^ = 0.09 + 0.04 = 0.13 (21) 



F 



Recomputing Equations 15 through 17, the result is 



= 0.10 (22) 



and then by Equation 18 for the Extremal Type I 



a„ = 0.10 (23) 



^R 



18. The error in the extremal prediction to a very rough approximation 

 is about one-tenth of a meter. It is not yet known how accurate this error 

 estimation technique is, and its results should be used with some subjective 

 consideration. 



Wave Period Distribution 



19. The joint probability distribution for significant wave height ver- 

 sus period is listed in Table 9. For the extreme wave condition, the periods 

 tend to be larger than 12 sec with periods at 14.3 sec for the three most ex- 

 treme conditions in the 20-year period. This tendency suggests the use of a 

 period of near 14.3 sec for the computation of design conditions. 



^R 



19 



