Sunday, June 04, 2006

Hurricane Katrina: Good News for Flood Control Engineering

Last August's Hurricane Katrina left well over a thousand people dead, most of New Orleans flooded, and many thousands homeless. You have to look long and hard to find any good news in the aftermath of the worst natural disaster to hit the United States in many decades. But ironically, one of the best things that may happen as a result is a badly needed top-to-bottom reorganization of coastal flood control work.

Engineer and author Henry Petroski likes to say that engineers learn a lot more from failure than they learn from success. You have to know a certain amount in order to succeed at all, of course. But if you are a young engineer and you just apply book learning to a project where everything goes smoothly, all that tells you is that the books were right. Failure is Nature's way of telling an engineer that the books didn't tell the whole story, and that the state of the art needs improving. Katrina overwhelmed a complex system of levees, dams, and canals that clearly wasn't up to the challenge. But now everybody concerned is motivated to find out what went wrong and how to fix it in a way that will prevent another Katrina disaster.

On June 1—the start of the 2006 hurricane season—the U. S. Army Corps of Engineers released a huge, detailed report on the failures that contributed to the New Orleans floods. More important than the details of the report is the fact that the Corps accepted full responsibility for the failure. The Corps and the Mississippi go back more than a century, to the days when many people doubted that the Big Muddy could ever be contained or controlled by the works of man. In "Life on the Mississippi," Mark Twain's memoir of his years as a riverboat pilot, he reports on how bold engineers had just begun to erect levees and dams to channel the river's unceasing powerful currents in the 1880s. Despite Twain's generally optimistic attitude toward the modern age's advances in technology, he expressed considerable skepticism that the Corps of Engineers, or anyone else short of the Almighty, could make much of a difference in the way the Mississippi found its way to the sea.

In the intervening decades, the Corps found ways of doing just that. The South still saw severe floods from time to time. In 1927, the Mississippi inundated hundreds of square miles of Delta land, and 1965 a hurricane caused serious flooding in New Orleans. And here we are in 2006, a year after another major flood-control disaster. It may not be entirely coincidental that these events are about a generation apart. A pattern Petroski has found over and over in the history of technology goes like this: In the early stages of a new technology, engineers tend to overdesign a system to make sure it doesn't get a bad reputation that would kill it off right away. But as more designs succeed, newer engineers on the job tend to become not exactly careless, but overconfident. It's easy to assume that because there haven't been any major problems so far, there aren't likely to be in the future. This is when new circumstances or long-term failure mechanisms are most likely to cause trouble. What we may be seeing here is a pattern of disaster, followed by a few years of overcautious design, followed by reduced attention, less funding, and complacency, and a new generation of engineers who aren't old enough to remember the last big failure, who arrive just in time for the next one.

But there are other factors as well. A system of dams and levees protecting a certain land mass has one thing in common with power lines, high-voltage insulation, and chains. All it takes is one failure in one little place—one tree touching a sagging transmission line, one piece of insulation failing, one link breaking—and the whole system collapses. Enough water can—and did—flow through a twenty-foot breach in a dike to flood most of a city like New Orleans. Historically, the best way engineers have found to deal with such chain-like systems is to design and build them consistently, to uniform plans, and perform a rigorous and thorough quality-control inspection to make sure every single part of the system is up to snuff.

Unfortunately, it appears that the political structure of New Orleans at least partly militated against such a procedure. Although the U. S. Corps of Engineers had overall responsibility for the integrity of the flood-control system for New Orleans, there were also state and local authorities whose job it was to inspect and maintain parts of the system. I almost wrote, "critical parts," but in a system of dams, every single part is just as critical as every other part. In the nature of things, some parts of the system received better attention than others. But Katrina went for the weak spots regardless of politics, and the result filled New Orleans with filthy water and emptied it of people.

The good news I referred to above is that no one now needs convincing that the old way of doing flood-control business along the Mississippi, and especially in New Orleans, doesn't work. There were many technical problems with the levees such as inadequate construction and failure to take into account the poor quality and subsidence of the soil. People are now discussing the construction of "fail-safe" levees that have secondary landfill areas behind them, but of course, that takes up valuable real estate. What should result from the sad images we saw of flooded New Orleans is a revitalized and chastened Corps that will coordinate with reorganized state and local authorities to do a good job next time. It will take money and political will, but the alternative is too fresh in our minds to allow them to do anything less—at least for the next thirty years.

Sources: The U. S. Army Corps of Engineers draft report released June 1, 2006 is currently online at A personal recollection of the 1927 Mississippi floods is contained in the memoir Lanterns on the Levee: Recollections of a Planter's Son by William Alexander Percy, who was author Walker Percy's uncle.

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