proportionality constant dependent upon the coastal position. For example, 

 K may "be determined for the open coast in the vicinity of the San Antonio 

 Bay region by considering "the "Beta Hurricane" of large radius (LR) and 

 medium forward speed (MVp ) (see Table 2).' The values of CPI . R and Vp are 

 27-^5 5 2h, and 11, respectively. From Figures 15, l6, and 17 , the corre- 

 sponding frequency ratios are 0.02, 0.69, and 0.5, respectively. Equation 

 (8) gives: 



P = K (0.69) (0.5) (0.02) (||-) 100 = .1987K 



K now may be evaluated since P has been determined previously from the 

 generalized frequency analysis and has a value of about O.985. Hence K 

 is equal to about U.96, and is taken to be constant for this specific 

 location. With the known proportionality constant, all other hypotheti- 

 cal hurricane frequencies may be evaluated including any storm of record. 

 For example, the return frequency of the severe storm of 196I (Car la) 

 which occurred near this position (taken to be the exact location) can 

 be evaluated and given by: 



P = (I+.96) (0.765) (.055) (.058) (||-) (100) = 0.35 events per 100 years. 



This equation indicates that a storm equivalent to Hurricane Carla may 

 occur about once every 289 years. The probability frequencies are tabu- 

 lated for all hurricanes in Table 1. Note that all frequencies do not 

 appear to be consistent with the severity of the storm - for example, 

 the 1915 storm. However, it must be remembered that a hurricane which 

 produces a high surge on the open coast is not necessarily a very in- 

 frequent one, since each parameter contributes to its probability of 

 occurrence. Surely, errors are also involved in the prediction scheme 

 and certainly the parameter magnitudes given are only an approximation, 

 particularly those recorded in the early part of the century. In any 

 event. Equation (8) should give a reasonable approximation of the 

 hurricane frequencies that can be expected by actual occurrences. 



The advantage and the primary importance of Equation (8) allow one 

 to assign frequencies to hypothetical hurricanes of prescribed parameters. 

 The relation does not indicate the storm surge frequency associated with 

 the hurricane, but merely indicates the frequency of the tropical cyclone. 

 This can only be useful to coastal engineers in resolving design problems 

 where a hurricane frequency criterion must be established. 



Section IV. REGRESSION ANALYSIS 



Although not used in connection with the present study, the tech- 

 nique of Multiple Linear Regression Analysis was employed in an attempt 

 to correlate the hurricane parameters and basin characteristics with the 

 open-coast peak surge height. None of the correlation results obtained 

 were satisfactory; the final relation derived is presented only for the 

 purpose of comparison by subsequent similar investigations. The first at- 

 tempt to find the correlation of the variables was made at the U. S. Army 

 Corps of Engineers, Hydrologic Engineering Center, Sacramento, California . 



27 



