Surviving the Next Katrina

by Jonathan Cohn | August 19, 2010

Note: This is part of a week-long series on New Orleans, five years after Katrina, based in part on my recent rip there.

Everybody wants to know whether New Orleans can survive the next big hurricane. Few of them realize that it should have survived the last one.

Katrina was not a category five storm and it didn’t even hit New Orleans directly. At the last minute, it veered northeast, making its final landfall on the Mississippi Gulf Coast. Katrina was massive enough to inflict damage far away from the eye, so it was bound to take its toll on New Orleans, too. But if not for a series of human errors, some of them dating back decades, the flooding would have been far less severe.

Katrina’s toll prompted investigation and litigation. But what about action? To get some answers, I consulted two of the area’s leading authorities on hurricanes and the environment: Mark Schleifstein, the Times-Picayune writer who’s covered the beat for two decades, and Mark Davis, who is director of Tulane’s Institute on Water Resources Law and Policy. Their shared verdict: The city is safer than it was before Katrina and still not as safe as it should be.

The linchpin of the city’s hurricane protection is its levee system, which is among the world’s largest. The concept is pretty simple. New Orleans is basically a set of three bowls that sit below sea level. To keep the water out, the Army Corps of Engineers put levees around the city--i.e., it built up the sides of the bowls. But the Corps didn’t build the levees very well. They used dated and inaccurate measurements of ground height, so that the levees were shorter than they were supposed to be. They also built on unstable foundations, with pilings that were too short or too weak to anchor the walls in the ground.

Still, the levees should not have been the city’s only line of defense--and would not have been, if not for decades of development undertaken in the name of commerce. In its natural state, the Mississippi River carries silt, depositing it into a delta at the Gulf of Mexico and creating wetlands there. Wetlands are a natural hurricane barrier--preventing storm intensification, breaking surface winds, and dissipating surging waves. The conventional wisdom is that every five to seven miles of wetlands reduces overall storm surge by a foot.

But a silty, winding river isn’t that easy to navigate. And, starting in the late 19th century, public and private developers dredged, diverted, and narrowed the Mississippi. The currents became faster and, when that happened, the river stopped depositing so much silt in the Delta. The Corps also dug a new channel, called the Mississippi River Gulf Outlet, that gave ships a direct shortcut from the Port of Orleans to the Gulf. But this allowed salt water, from the Gulf, to flow back into the wetlands. (Wetlands need fresh water to survive.) Channels dug to provide access to oil exploration platforms had the same effect. According to Davis, the coastal wetlands once covered 4.5 million acres. Today they cover less than 2 million.

Katrina was not a perfect storm. But, thanks to those environmental changes, it was a perfect catastrophe. The Gulf Outlet acted like a water cannon, shooting water into the canal walls protecting the eastern neighborhoods of New Orleans. As the water level rose, it began to splash over the levees, eroding the foundation beneath--until the walls started crumbling.

Meanwhile, on the northern part of the city, rising levels in Lake Ponchatrain reversed the flow in the drainage canals, sending water into the city rather than out of it. The pumps, placed far from the lake, couldn’t push the water in the other direction. And those canals, too, had shoddy foundations--making it a matter of time before they began to fail, flooding most of the rest of the city. (The Times-Picayune eventually put together an animated webcast that shows the entire sequence play out, on a map.)

These failures should not have been surprises. Among those warning of levee problems before the storm were Schleifstein and some colleagues at the Times-Picayune, who wrote an award-winning series pointing out the inaccurate height measurements. The series title was "Washing Away: How south Louisiana is growing more vulnerable to a catastrophic hurricane." As Michael Grunwald, whose extensive invesgitations of the Corps of Engineers also predate Katrina, later wrote in Time magazine,

The Federal Emergency Management Agency (FEMA) was the scapegoat, but the real culprit was the U.S. Army Corps of Engineers, which bungled the levees that formed the city's man-made defenses and ravaged the wetlands that once formed its natural defenses.

Planning for the next hurricane, though, couldn’t wait for recriminations. With approval from local officials, Congress ordered the Corps to rebuild the levees--and to build them better this time. The plan that emreged had three phases (1) immediate repairs of the breache dsections, including efforts to fortify foundations with concerte splashguards (2) improvement of the levees so that they were able of protecting the city from a “once-in-a-hundred-years” storm, as they were supposed to be before Katrina (3) further strengthening of the levees, coupled with wetlands restoration, so that New Orleans would be safe even from a a “once-in-a-five-hundred-years” storm.

How much of this plan has been realized? The Corps have made a lot of progress on parts one and two (which eventually merged into one project). And while you would certainly be forgiven for skepticism, given previous promises, both Davis and Schleifstein seem to think the improvement is real. “We’re a hell of a lot better than we were before Katrina--no question that the levee system is dramatically better,” says Schleifstein.  

Progress on the third stage has been more halting. The Corps did shut down, and dam, the Gulf Outlet--which may not stop a storm surge from coming through but will help keep salt water out of the wetlands. In 2007, Congress passed and President Bush signed the Louisana Coastal Preparations Act; President Obama’s budget proposes to give it real money. And while virtually every effort at wetlands reclamation has run into resistance from stakeholders, particularly the oil industry, virtually all politicians at least pay lip service to the idea--and, in the wake of the Deepwater Horizon spill, efforts to protect the wetlands seem to be gaining momentum.

Still, the actual reclamation of wetlands hasn’t really begun--and, once it does begin, it will take years, even decades, to finish. Meanwhile, global warming is really raising sea levels and, perhaps, spawning stronger storms. “We don’t get to grade on the curve on this,” Davis says. “Doing better is not a substitute for doing what is essential. Time is not our friend and time is running out.”

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