Levee Design

Here's an extract from an article that provides some insight into the matter of the levee design that's already a topic for critics.

A category 6 hurricane could hit any coastal area of our nation tomorrow and cause massive destruction. Even if we built a 30 foot high 250 foot wide reinforced levee around every mile of our coast line it still could not be guaranteed it would prevent all damage. Nothing we do is absolutely fail-safe, perfect, or permanent even if it's expensive. All things designed and built by mankind are, at best, compromises of knowledge, skill, time, money, and other factors. We are frequently humbled when we think we have it all mastered.

The whole Mississippi River valley has been prone to flooding since man first came to settle here. Thanks to a lot of hard work by a lot of people we have much better flood control structures. But it is still an imperfect system. There has been far less suffering from flooding in the lower Mississippi River valley than just a few generations ago. Never the less, there is still flooding when levees break because, like all things man made, they can and do fail. Knowledge of how to design these structures continues to improve. Arguments still continue as to what's best. Folks in one area want the water diverted to another. The conflict in Louisiana itself over the Mississippi verses the Atchafalaya continues to this day. There are compromises with everything that's been done and everything we could do.

Due diligence, honest evaluation, reasonable assumptions, etc. are all to be expected. Perfection and accurate prophecy can not to be assured.

 

After something happens, its probability always seems greater. That's true whether it's a 200 yr. hurricane, a 100 yr. flood, a pregnancy, an airplane crash, or a heart attack. People of New Orleans now know a hurricane can hurt them badly and for them it was a 100% chance. To them the 0.5% number is, indeed, ridiculous.

Probabilities of natural disasters are estimates based on known historical data. I'm sure we all understand this and many of you better than me. We all use this kind of data to make decisions about what to do and where to spend limited funds and devote limited resources. We can not eliminate all risk and even if something has a 0.5% risk of happening in 200 yr. that doesn't mean it won't happen tomorrow and again the following day for the next 200 yr. period.

The situation thirty years ago, when the last major upgrade to levees were designed, probably relied more on the protection of the Lake Ponchartrain Basin to break the force of hurricanes than would be done today given the extensive erosion of that buffer. The four major hurricanes (1947, Betsy, Camille, and Georges) that came near New Orleans prior to Katrina were all category 3 or less after they hit land. Hurricane Betsy in 1965 elevated the concern in New Orleans and that concern elevated the levees. Hurricane Camille in 1969 was the worst prior to Katrina. Hurricane Georges in 1998 resulted in more focus on improving the New Orleans levee system.

I don't know enough about the statistics to debate the precision of the 0.5% number. I'm not even certain if this was a literal value. The point I took from the comment was that an economic decision was made at the time to provide affordable protection for the most likely situation given a low probability for anything worse. Again, that plays into every decision for protective systems in our entire temporal existence. Every evaluation has to balance risk verses benefits with consideration to technical, economic, and political factors involved.

Lots of smart people step forward after something happens to point out the "would've, could've, should've" information. It's a lot harder to predict the future and do something about it before it happens.

The immediate focus needs to be on restoring order and providing humanitarian assistance to those in need. Later on we can, should, and will evaluate what should be done with respect to New Orleans and other coastal cities and towns. Blaming past decisions - decisions made of the best available data and limited by technology, funding, or other factors - will not help either today's problems or tomorrow's.

Technical, economic, and political factors will play into these future evaluations and compromises will be reached. Politicians will demand this and that as long as it gets attention, tax payers will balk at the costs, engineers will poor over the technological alternatives, environmentalists will have their say, etc. Probabilities - whatever they are - will have to be considered. People will choose to take risks, to continue living in vulnerable areas, and to balance the risk against the benefits of employment from the commerce of river and coastal enterprises. Something will be done but it will not guarantee that another future hurricane won't result in extensive damage to someone's homes and businesses.

How about that potential major earthquake that could hit the area between St. Louis and Memphis? What should we do about that probability?

 

'2001: FEMA designates a major hurricane hitting New Orleans as one of the three "likeliest, most catastrophic disasters facing this country."'

- LINK </font>[/QUOTE]That's a good point but it's from the perspective of FEMA's planning for possible natural disasters and not the probability of levee failures.

 

Earthquake proof or resistant? To what level of earthquake? Homes or business or both? What about historical buildings? How about other structures? Over how wide of area should this be done? How much will it cost? Who will pay for it? Which locations should get this done first? How long should it take start to finish? What if something happens before then? What if some people don't want to do? Is it Constitutional? Is it a local, state, or federal role? Should the government seize private property that's not compliant with new standards? Etc.

 

The Dutch have some real interesting tidal wave control structures and systems. They've built a large part of their little country on land claimed for the sea out of necessity.

 

By the way, this FEMA quotation that's floating around - the "three likeliest, most catastrophic disasters facing this country" - bears a bit more investigation and comment.

The quotation seems to originate from a rather prophetic article by Eric Berger titled "Keeping Its Head Above Water: New Orleans Faces Doomsday Scenario" published 1 Dec 2001 in the Houston Chronicle.

The words quoted are not those of FEMA but, rather, of Berger. I've yet to find the original FEMA document from which this was derived.

I don't doubt that FEMA would have considered these as scenarios around which to base plans and exercises. However, I'd just like to keep the facts pure and read the original information in its original context. I'd like to read exactly what they said not just what Berger wrote about what they said.

 

Regarding advance "warning", I'll add that my own Father, who was heavily involved in disaster response on at least four occassions, said back in the early 1960's that New Orleans would some day experience major flooding from rupture of the levee system following a major hurricane. He didn't have any scientific data to back that up. He just believed it from looking around at the results of other Gulf Coast hurricanes and from the history of flooding in the Mississippi River delta.

By the way, he also had his government issued camera stolen in front of the Federal Building in New Orleans while there to help out following a hurricane. He was madder than an hornet about it! He couldn't figure out why people he was there to help would steal his equipment. New Orleans has never been a particularly "safe" city and the local politicians don't have very good reputations.

Most people that have lived on the Gulf Coast, including me, "knew" that someday New Orleans, or maybe Lake Charles, would get hurt bad. So, regardless whether FEMA said so or not, whether the government "warned" them or not (they did), whether levees were under built or not, etc., people have been aware of the risk for a long time. Most, probably like most of us, just figure it won't happen on their shift. We all just keep figuring the gains outweighed the risks. That's why we still get on that airplane and turn over the "driving" to somebody we don't know.

Let's be real careful about blaming our government for what we've known and accepted for a long time.

 

All things must be considered!