equation (A-4). Values for the parameters Hs, and a in equation (1) are 
easily calculated from a and b by using the relationships defined for 
equation (A-4). 
The distribution function given by equation (1) with the estimated para- 
meters Hoo min» Hsc; and a is compared with the empirical distribution. 
A new value of Hgc min is estimated to attempt a better fit to the empirical 
distribution. The new Hgce min is used to compute a new table of X and Y 
values which is then used to estimate new values of Hc and a as before. 
The process is continued until an Hgce min has been found which leads to a 
satisfactory model. The parameters for Nags Head in equation (2) are con- 
sidered satisfactory because they specify a distribution function which fits 
the lower 99 percent of the empirical distribution reasonably well but is con- 
servatively high in comparison to the highest 1 percent of the empirical dis- 
tribution. Since the highest part of the empirical distribution is based on 
the smallest number of observations, it is the least well-established part of 
the empirical distribution, and conservatism is desirable in a model for engi- 
neering use. 
16 
