7. Final Generalized Surge Frequency 



Because relatively few hurricane events are available for the surge 

 frequency analysis, it -would appear justifiable to envelope curves 1 and 

 2 on Figure 5 to provide a more conservative as well as reasonable hurri- 

 cane surge frequency estimate. The enveloped curve, although not shown, 

 was employed in reversal of the procedures to construct the generalized 

 hiirricane-surge frequency indicated on Figure 6. The relation shown on 

 this fig\ire pertains only to surge-height frequencies associated with 

 full-scale tropical hurricanes; however, other factors can influence the 

 lesser surge heights that make up the entire spectrum. These factors 

 can be attributed to local meteorological conditions such as strong winds 

 directed over the sea in a shoreward direction, tropical depressions, and 

 peripheral hurricane surges. Nonhurricane surge heights above 2 feet MSL 

 occur more frequently than those of similar magnitude associated with 

 hurricanes, and therefore must be coupled with surge frequencies derived 

 in the prior investigation to obtain a relationship consistent with the 

 problem. 



Because of the longer period of tide records available for Galveston, 

 this station again was selected for making a surge frequency investigation 

 of surges for all water level elevations equal to or exceeding 2 feet above 

 mean sea level. The surge frequency curve derived from this analysis was 

 combined with the one obtained from the final hurricane-surge frequency 

 for Galveston. The two curves were connected at a point where the corre- 

 sponding surge height was about 6 feet above mean sea level which indicates 

 that surge heights above this elevation are generated only by tropical 

 hurricanes. On the basis of this relationship and by reverting back to 

 the generalized form, the final open-coast surge frequency estimate was 

 obtained as shown on Figure T- The surge frequencies at various locations 

 along the Texas Coast derived from the final generalized surge frequency 

 relationship is indicated on Figures 8 through 13. Figure ik shows the 

 surge heights along the coast that could be expected for corresponding 

 exceedence frequencies of 5, 10, 25, 50, and 100 years. 



14 



