to Atlantic City to affect the water level; (b) alongshore hurricanes which pass to the east of 

 Atlantic City but do not come inland near enough for the landfall of the storm to affect the 

 water level at Atlantic City; and (c) extratropical storms. Myers tabulates the estimated 

 probability that a surge in each height interval will occur at Atlantic City witliin a year from 

 each class of storm. The probabiUty that the combined storm surge and astronomical tide 

 will exceed any level is obtained by combining the astronomical tide probabihties with the 

 surge probabihties for that class of storm. The probabiUty that a given level will be reached 

 by any type of storm is obtained by adding the probabihties that the given level wiU be 

 exceeded by each type of storm. This can be illustrated sufficiently by considering only one 

 storm type. 



Table 16 is used to illustrate the method for combining meteorological and astronomical 

 probabihties. Surge heights are given for increments of 0.2 foot. Compatible increments 

 must be used for the astronomical tidal heights. Since the astronomical tidal height 

 probabihties can be obtained with much greater confidence than the surge increments, an 

 increment of 0.1 foot is selected to demonstrate the method of combining probabilities for 

 a case in which the two functions are not known with equal precision. The, two semidiurnal 

 tide waves at the reference station, Sandy Hook, and at Atlantic City are very similar. 



Table 16. Frequencies of maximum winter (November to April) 

 surge heights, Atlantic City, New Jersey. 



Surge 



Frequency' 



Surge 



Frequency 



(ft) 



(per season) 



(ft) 



(per season) 



2.0 



1.2 



4.4 



0.019 



2.2 



0.80 



4.6 



0.016 



2.4 



0.60 



4.8 



0.011 



2.6 



0.45 



5.0 



0.009 



2.8 



0.30 



5.2 



0.006 



3.0 



0.20 



5.4 



0.005 



3.2 



0.16 



5.6 



0.0035 



3.4 



. 0.11 



5.8 



0.0027 



3.6 



0.08 



6.0 



0.0021 



3.8 



0.05 



6.2 



0.0013 



4.0 

 4.2 



0.04 

 0.03 



6.4 



0.0011 



Total 4.10 



' Data from Table 7-3 m Myers (1970). 



Therefore, it will be sufficient to consider only the semidiurnal tide since only the peak 

 values of the storm surges are given. The demonstration calculation is hmited to a 

 combination of predicted high waters and peak surges, which provides a conservative 



83 



