HURRICANE SURGE FREQUENCY: ESTIMATED FOR THE GULF COAST OF TEXAS 



Section I. INTRODUCTION 



Dangerous and. destructive tropical cyclones (hurricanes) can be ex- 

 pected to cross the Texas Coast on the average of about once every three 

 years. In the present century alone, twenty full-scale hurricanes have 

 hit this coast, some were extremely severe, others less severe, but all 

 were destructive. The great storm of 1900 stands above all others, be- 

 cause it took the lives of about 6,000 people on Galveston Island. Had 

 major steps not been taken with respect to storm warnings and deployment 

 of h\irricane protection systems, it would surely have been possible for 

 the later, more severe hurricanes to cause considerably more deaths than 

 the 1900 storm. Seawalls were ^constructed along the beach fronting the 

 city of Galveston, and this line of protection has prevented any recur- 

 rence of a catastrophe with an order of magnitude of the 1900 hurricane. 

 Over the past several decades, tropical cyclones have caused property 

 damages that ran into billions of dollars. Hurricane Carla (1961) caused 

 damages in excess of $U00 million. The hurricanes which cross the coast 

 with an average frequency of about once in three years have taken a high 

 toll in human lives and property damage. 



Although strong hurricane winds and the tornadoes spawned during the 

 course of the h\irricane cause great loss of life and property, the high 

 surge produced is the most destructive component on the Texas Coast. In 

 general this is because the land slopes gently from the sea toward the 

 hinterland. The violent winds associated with a hurricane drive the sea 

 over the low- lying terrain into the shallow bays, rivers, and tributary 

 streams. A single severe hurricane can flood vast land areas. For example. 

 Hurricane Carla (1961) flooded more than 1.5 million acres of land. The 

 abnormal rise of the sea surface on the Texas Coast brought about by 

 tropical hurricanes is indeed the most destructive factor. 



Coastal engineers must design hurricane-flood protection projects to 

 combat the onslaught of tropical cyclones in order to protect lives and 

 property. To accomplish this mission, the engineer not only must know 

 how high the surges will be for the expected future hurricanes , but also 

 the frequency of their return. In other words, a design surge must be 

 prescribed when levee and seawall heights are to be established, and the 

 frequency of this surge must be estimated. Surge heights and related 

 frequencies must also be estimated for those storms that fall below the 

 one chosen for the design so that economic feasibility studies can be 

 carried out. Clearly, the line of protection should not be designed in 

 such a manner that total failure could occur during a very severe and 

 infrequent hurricane. Thus the coastal engineer should have some in- 

 sight in the maximum probable surge height and its associated frequency. 

 Consequently, the coastal engineer must be able to predict the surge 

 heights over a wide spectriom as well as the related return frequencies 

 to obtain the best design for hurricane-flood protection works, from the 

 standpoint of safety and cost . 



