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My personal musings about anything that gets on my radar screen--heavily dominated by politics.

2005-09-02

Did Pompeiians Blame The Emperor?

I, like most of us, are getting to know the city of New Orleans much better in the last few days.

For instance, I did not know that most of the city is below sea level, with the high point in the city being at about the same elevation as the natural bank of the Mississippi River. I also did not know that the city is shaped basically like a bowl, with the Mississippi making up one of the borders; just for good measure, Lake Pontchartraine makes up one other border, and the Gulf of Mexico effectively makes up yet another border. Yes, that’s right, they built this city in a low flood plain bordered on three sides by volatile bodies of water.

A little like building a city at the foot of an active volcano. Oh, wait . . .

The city has been protected for many years by a lengthy (some 475 miles worth) system of levees which control the flow of the Mississippi and contain the Lake. These levees were built 40-some years ago by the Army Corps of Engineers, and were designed to withstand what they thought at the time was the historical equivalent of a catastrophic storm.

For some background on that, here’s a good investigative article by the New Orleans Times-Picayune from 2002 on the history and upkeep of the levees. For some background:

The corps' original levee specifications are based on calculations made in the early 1960s using the low-tech tools of the day -- manual calculators, pencils and slide rules -- and may never have been exactly right, corps officials say. Even if they were, corps officials and outside scientists say levees may provide less protection today than they were designed for because subsidence and coastal erosion have altered the landscape on which they were built. . .

Thanks to its low, flat profile and its location on the Gulf of Mexico, south Louisiana is more at risk from a major natural disaster than most other places in the country. The risk of a catastrophic levee-topping flood in New Orleans is roughly comparable to the risk of a major earthquake in Los Angeles. Because of coastal erosion and subsidence, that risk is growing.

But judging that risk and how to protect against it can be difficult. Recent experience tends to confirm the idea that catastrophic hurricane floods are rare. Even if a powerful hurricane comes close to New Orleans, only certain storm tracks could flood all or part of the city and suburbs. Twelve storms rated Category 3 and above have hit the Louisiana coast in the past 100 years, but only four produced major flooding in the New Orleans area. The levee system was built largely in response to those storms, to prevent or reduce flooding in similar events.

Obviously, there was a design flaw in the city that was just waiting for a force of nature to exploit it.

Statistically speaking, not very many hurricanes have hit the New Orleans area -- at least not enough to allow a solid projection into the future.

And the recent past isn't always an accurate basis for predicting the future. A Science magazine paper written last year by meteorologists William Gray, Christopher Landsea and Stanley Goldenberg predicted that based on long-term trends in sea-surface temperature, the Atlantic Ocean is entering a 10- to 40-year period of more intense hurricane activity. That means more big storms may menace areas that are more heavily populated than during the previous such cycle, from 1920 to 1960.

Storm surges are even harder to analyze. Flooding can vary dramatically mile by mile, even lot by lot, depending on the storm, rainfall, land elevation, levee heights and proximity to waterways and drainage pumps. Storm surges flowing into Lake Pontchartrain literally slosh around, first raising water heights to the north and west, then on the south shore.

A record-setting rainfall could swell water heights by a foot or more, something that could turn a relatively weak storm into a killer.

Hurricane flood statistics are even spottier because scientists often did not have the equipment positioned in enough places to measure high water during past storms. The landscape also is changing because of coastal erosion, sinking and even levee building. So a flood height from the past wouldn't be the same today.

So, you would suppose, efforts have been made to study the changes and to evaluate how effective the levee system is using more modern equipment and records. And, just such an effort was made, but . . .

A 1996 attempt to study Lake Pontchartrain-area levees broke down over that dispute and because of bureaucratic disagreements, according to Combe and others involved.

Meanwhile, sinking, erosion and sea-level rise mean that the odds of getting flooded have been getting worse across south Louisiana. "The frequency of flooding is increasing at all levels," Suhayda said. "You might find in 50 years that the risk of these infrequent events doubled. The 50-year event became a 25-year event, the 100-year event became a 50-year event."

All of this information might lead one to a rather inescapable conclusion: New Orleans was at risk.

"I think everyone familiar with this is sitting on pins and needles because nothing has happened in that lake for 50 to 60 years and you start to think, are we due" Butler said. "And the answer I think is yes, statistically you're due. And that's scary. Based on my knowledge of hurricanes, I'd watch what happens very closely -- and I'd get out of Dodge."

The group tasked with the upkeep of the levees is the Army Corps of Engineers. And many have been carping in the last few days about how dramatically the Corps has been underfunded. But a February article points out that even full funding of what they proposed for this year would have made no difference.

The U.S. Army Corps of Engineers has identified millions of dollars in flood and hurricane protection projects in the New Orleans district.

Chances are, though, most projects will not be funded in the president's 2006 fiscal year budget to be released today. . .

The most urgent work being delayed by funding shortfalls involves levee construction on the West Bank.

Unfortunately, the main levee that broke and caused the vast majority of the flooding in the city of New Orleans was the 17th Street Canal Levee, which, according to the NYTimes (with a hat tip to RedState) was just recently upgraded.

No one expected that weak spot to be on a canal that, if anything, had received more attention and shoring up than many other spots in the region.

It did not have broad berms, but it did have strong concrete walls.

Shea Penland, director of the Pontchartrain Institute for Environmental Studies at the University of New Orleans, said that was particularly surprising because the break was "along a section that was just upgraded."

Sadly, as Katrina bore down on the Gulf Coast, Matt Crenson of the Associated Press published a sadly prescient article on Monday.

Experts have warned for years that the levees and pumps that usually keep New Orleans dry have no chance against a direct hit by a Category 5 storm. . .

The center's latest computer simulations indicate that by Tuesday, vast swaths of New Orleans could be under water up to 30 feet deep. In the French Quarter, the water could reach 20 feet, easily submerging the district's iconic cast-iron balconies and bars.

Part of the problem, as Crenson points out, is that NOBODY has much experience dealing with catastrophic events of this nature.


Aside from Hurricane Andrew, which struck Miami in 1992, forecasters have no experience with Category 5 hurricanes hitting densely populated areas.


“Hurricanes rarely sustain such extreme winds for much time. . .” National Hurricane Center meteorologist Richard Pasch said.


“We haven't seen something this big since we started the program,” said Kurt Gurley, a University of Florida engineering professor.


Crenson also mentions the real culprit, which, as noted before, IS NOT the condition of the levees.


Experts have warned about New Orleans' vulnerability for years, chiefly because Louisiana has lost more than a million acres of coastal wetlands in the past seven decades. The vast patchwork of swamps and bayous south of the city serves as a buffer, partially absorbing the surge of water that a hurricane pushes ashore.


Experts have also warned that the ring of high levees around New Orleans, designed to protect the city from floodwaters coming down the Mississippi, will only make things worse in a powerful hurricane. Katrina is expected to push a 28-foot storm surge against the levees. Even if they hold, water will pour over their tops and begin filling the city as if it were a sinking canoe.


After the storm passes, the water will have nowhere to go.

So, you might ask, what is the point?


Well, the point is several-fold. First, information: I had no idea about the layout of New Orleans or exactly what was involved in the levees. I thought it was interesting, so I shared. Secondly, it’s easy to start pointing fingers and assigning blame, but there’s really very little anybody could have done—the President or others—to stop this. Even the most recently refurbished levee was incapable of holding back the flooding, which was at a level and degree that had never been seen before, and only happens once every century. For all we know, better levees might have only exacerbated the problem. And, no, global warming had nothing to do with this—this is part of the cyclical nature of severe storms.


But mostly, just to point out what should be obvious: every once in a while, Mother Nature sends something our way to remind us who’s boss. And, as John McPhee pointed out in his book The Control of Nature, when she does, it’s best just to get out of the way, and Pray to the Heavenly Father [I don't think McPhee said that last part].

I wonder if the survivors of Pompeii blamed the Emperor.









Posted by: Michael / 9/02/2005 12:28:00 PM

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