Dear Senator Obama,

I was not able to attend your rally today at Tulane University in New Orleans, but I did read your scripted remarks online.

I want to thank you for taking a strong stand in support of building significantly improved hurricane protections around the New Orleans area. I particularly appreciate your use of the words, "Never again." This is truly a level of commitment that no one in Washington--with the exception of the Louisiana delegation--has dared articulate. Again, thanks.

I would also like to ask a favor of you. It is a simple thing I am asking, but I hope you will recognize how vitally important this is to citizens in Louisiana--and many more citizens across America--who live with the risk of flooding daily.

In your speech, you refer to the current objective to provide protection from a "100-year storm."

Senator, I must tell you there is no such thing as a "100-year storm."

The terminology "100-year flood" or "100-year storm" may be popular in the common vernacular, but it is patently misleading. What we are really talking about is the flood or storm that has a 1 percent chance of occurring or being exceeded in any given year. It is a theoretical weather event that is used to benchmark the risk of flooding.

Such careless terminology encourages the belief that such storms are rare and only occur once in a lifetime or less. Unfortunately this is not the case.

That 1 percent chance only applies to one year. Once we experience a "bad" year, there is no assurance whatsoever that we will have 99 "good" years. We could, in fact, see two consecutive "100-year" hurricanes occur in back-to-back years.

We need only recall the hyper-activity of tropical cyclones in the Gulf of Mexico in 2005 to recognize that large back-to-back storms are not some distant probability. Hurricanes Katrina, Rita and Wilma all reached Category 5 status on the Saffir-Simpson scale in just a single hurricane season.

In fact, statistics reveal how common that "100-year" event can be. There is a 26% chance that a 1% storm or flood will occur within 30 years. And there's a better than 50% chance that a person will experience the 1% flood within a normal lifetime.

Once in 100 years? Not by a long shot.

And so the favor I ask of you is that you take care to use the correct terminology when talking about hurricane and flood protection. Could you say, "1 percent per year chance of exceedence," or, "1 in 100 chance per year of being exceeded." In my work as a Civil Engineer, we often call it the "1% storm" for short.

Because Americans are looking to you for leadership, it is imperative that your proposals regarding hurricane protection be as accurate and precise as possible. The risk we face from flooding and hurricanes is real and must not be carelessly dismissed or misrepresented. That's the mistake we made before.

I hope I will again hear that you say, "Never again" when talking about hurricane protection. That's the kind of commitment to protecting Americans that can really make a difference and improve the quality of life for all.

Respectfully,

Tim
http://www.timsnamelessblog.blogspot.com/

(This letter was suggested by Maitri.)