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Day 642: The Reason For The Season

Hurricane season, that is, and I’m reading this article in today’s Washington Post, a longish piece on the current state of our storm surge protection (and which touches on the bewitched, bothered and beleaguered Road Home program and Nagin’s recent SOTC speech).

But could the rebuilt defenses handle another Katrina? The answer is no. Even by Army Corps of Engineers estimates, another Katrina would send storm surge from the Gulf of Mexico cascading over the walls that protect the Lower Ninth Ward from inundation.

… Col. Jeff Bedey, who is leading the Army Corps work in the city, identified the flood protections along the Industrial Canal — the one that flanks the Lower Ninth Ward to the west — as the system’s “Achilles’ heel.” In a major hurricane, storm surge from the Gulf of Mexico presses into Lake Borgne and then into the canals, possibly overtopping them.

Question(s) 1: Since Category 2-3 Katrina made landfall at Buras, Louisiana and its eye travelled east of here laying wasted to all in its path, does this mean that another hurricane traveling a Katrina-like path will cause spillover? Is there an equation that relates storm intensity to storm surge height? Also, how far east can the actual storm travel to create significant storm surge here? In other words, what’s the storm surge radius of such a storm?

… nearly two years after the storm, with the feasibility of protecting the city to that level under study, a project to defend the city from less-ferocious storms is proving far more expensive than anticipated. Meanwhile, the Bush administration has signaled that its commitment does not extend to Category 5 protection.

Question 2: Following from the previous question, forget Cat 5 protection, is this city protected against up to Cat 3 storm surge?

For any given year, the roughly 1-in-100 chance of a storm overcoming the defenses might sound like attractive odds … The 1-in-100 annual chance means that, over a lifetime, such an event is more likely to happen than not. Moreover, protection against the 100-year storm is far less than would be necessary for a Hurricane Katrina, which is considered a 400-year event, and certainly less than what could withstand a direct hit by a Category 5.

In Can Science Outwit Storms Like Katrina?, the New York Times explains that the latest 1-in-100 number comes from a new round of Defense Dept. dynamic computer modeling. One of the fallouts from that study is that the Army Corps of Engineers currently experiences “a lull in moving on to the next major step: raising the level of protection to meet the challenge of a 100-year storm, the kind of hurricane that might have a 1-in-100 chance of occurring in any given year.”

As someone who works in predictive capability, I know that a system as complex as a hurricane has way too many variables for scientists to satisfactorily generate such odds, regardless of supercompute power. Granted, newer hurricane simulations include the production of “surge and waves that have profound effects on coastal areas in the days before it actually hits land.” I also acknowledge that the system is not completely random (“storms in the Gulf do not behave randomly and come to shore anywhere, but are likeliest to follow certain sets of paths ” with New Orleans getting more than a random share of storms”). But, I would not stake my reputation, home or life on it … or those of coastal inhabitants relying on me for such an answer. This is precisely what laypeople and their representatives in government don’t (want to hear and) understand when they ask scientists to “put it in language my mama can understand.”

Question 3: Are you willing to live with these inconclusive odds? (There is no right or wrong answer.)

At the end of the day, a bad model is just interesting math, [Francine Berman, director of the San Diego Supercomputer Center] said. These complex models are incredibly hard to get right. The first time out, it’s very unlikely that you’re going to get an accurate enough model, but you have to start with the best representational model you can come up with and iteratively improve it over years, decades ” even centuries. (emphasis mine)

My task this summer is to locate and eat at ALL of New Orleans’s Vietnamese restaurants before possible evacuation due to an infernal hurricane and probable attendant storm surge. Oh, and hurricanes, you’re on notice! (Thanks, Ray)

Hurricanes On Notice

2 comments… add one
  • Tim June 2, 2007, 6:14 PM

    Gosh, you sure have a lot of questions! You are correct that modeling storms is complicated and difficult, but we have no choice but to try. The latest ADCIRC modeling was calibrated using recent storms so I think getting the right output is not so far from reach.

    Every hurricane is different. What made Katrina so bad for us was the huge eye–30 miles wide. Camille was more powerful but was so compact–11 miles wide–that her destruction was considerably less.

    I’ve blogged dozens of times about this, but we’ve got to avoid obsessing on Katrina. That hurricane is over and will not come again. As the Army says, we can’t prepare for the future by practicing past wars. The next hurricane might be all wind and no surge.

    The White House has never supported “Cat 5” protection for the city. They’re doing everything they can to drag out and delay things so that the tough choice of whether or not to build it will fall on the next president.

    Sometime this summer the Corps is going to complete its analysis of the 100-yr elevations. I think you and I might be the only people I know who would like to read it!



  • Maitri June 2, 2007, 9:05 PM

    Tim, thanks for your reply. On the one hand, you advise us not to get stuck on Katrina because it’s over and will not come again but, on the other, state that the output of ADCIRC modeling, calibrated using recent storms, may give us the right output. So, Katrina is A (not the be all and end all) factor in this prediction exercise. Can you expound further on that? Thanks again!

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