OCEANOGRAPHY IN THE UNITED STATES 31 



the lake and you had a very liigh water level against the surrounding 

 levees on the south side. 



Finally, when the hurricane got past, the winds then came out of 

 the south and you can notice that the high water is pushed back up 

 against the north face of the lake. 



The next slide shows the large picture of the hour in which they had 

 the maximimi level against the south. This lake is about 30 miles 

 across and these hurricane winds of about 90 miles an hour were able 

 to create a differential elevation across that lake of about 20 to 25 

 feet and generate waves of about 8 or 10 feet in height which chewed 

 heavily against the levee on the south face. 



One of the great values to us was that it enabled us to evaluate 

 this wind stress as this water blew across this lake and the bottom stress, 

 the friction of the bottom against the water trying to retui'n as bottom 

 flow which I mentioned before. 



We were able to evaluate these things pretty well and able to put 

 them to the test in another instance. 



The next slide is a profile for hurricane Audrey which, as you may 

 recall, struck the Louisiana coast a couple of years ago. This is the 

 bottom profile of the gulf out about 400 feet in depth and coming to 

 the Louisiana marsh area. This is the computed wind stress that we 

 were able to compute from the weather pattern furnished us by the 

 Weather Bureau and then we were able to compute the supereleva- 

 tion of the water as this surge that was generated and to check our- 

 selves against the elevation they actually obtained on the shore. We 

 found that, if we applied these bottom stresses and these sm-face wind 

 stresses that we were able to compute this elevation of the hurricane 

 surge against the coast. 



The next slide is another study of hurricanes in w4iich we were try- 

 ing to find out the frequency or the violence of these hurricanes. We 

 studied 69 hurricanes in the gulf and the Atlantic in terms of expected 

 violence and what you could expect in 20, 30, 40, on up to 1,000 years, 

 and then we took that same study and applied it only to the Atlantic 

 hurricanes. 



We were quite interested to find that we got about the same degree 

 of expectancy of violence on the Atlantic and in the gulf. 



Incidentally, these are used in our economic studies to find out 

 how much protection can be justified. 



These are formulas to show the complexities we get into relative to 

 a stationary wind, a hurricane that has a circular path, a slow moving 

 hurricane and a fast moving hurricane. 



We find we have to adjust our basic concepts of wave generation 

 and fit them to each one of these changing conditions. 



The next slide. I think what I have discussed before has been 

 more in the nature of what we call this fundamental or oceanographic 

 research. As I mentioned, about half of our program is on this 

 business of engineering research. Here are a few of our studies. 



"Durability of Steel Sheet Piling in Shore Structures." The 

 economic life of this type of structural material. 



"Accuracy of Surveys in Surf Zone." This deals with how accurate 

 such surveys are. We use the sm-veys to determine the rapidity with 

 which the shore face is eroding. 



"Shock Pressures of Breaking Waves," and "Durability of Concrp^^-* 

 in Coastal Structm-es," are other studies. 



