Tornado-Proofing Cities in the Age of Extreme Weather

Tornadoes will happen—and some towns, like Moore, may even be hit multiple times. But there are steps we can take to make homes and schools more resistant to tornadoes—and ensure that people survive the next twister, even if property doesn't.

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Brennan Linsley / AP

A soldier walks past a home destroyed by the tornado that hit Moore, Okla., the day before, on May 21, 2013.

Right now the death toll from the massive tornado that hit Moore, Oklahoma on May 20 seems—thankfully—to be less than first thought. City officials now say that 24 people have been confirmed dead, down from 51 people last night, due to double counting of some bodies in the confusion. But the new number still includes 9 children, and the toll could rise as rescuers search through the rubble.

This is the second time in less than 15 years that the town of Moore, a suburb of Oklahoma City, has been hit squarely by a major tornado. That’s mostly down to bad luck—although Oklahoma City area might as well be the buckle of the tornado belt, as Alexis Madrigal points out in the Atlantic, the chances of actually being hit by a major tornado even in this danger zone remain low. Though I doubt that will provide much comfort to the grieving residents of Moore as they dig out from yet another destructive twister.

But as unlikely as a major tornado remains, the hundreds of twisters that touch down in the U.S. still cause major damage—second only to hurricanes, according to the reinsurer Munich Re. Few ordinary structures can withstand a direct hit from a tornado as strong as the one that passed through Moore yesterday, which now ranks as an EF5, with winds above 200 mph. Not much could have saved the homes and businesses destroyed by the Moore twister, but is there a way to ensure that the lives of people in tornado country can be protected from extreme weather?

The answer is yes—with the right policy and the right incentives. But first we have to understand how the risks from extreme weather are changing—and for the most part, increasing. (Hat tip to Andrew Revkin of Dot Earth, whose post earlier today touched on much of this material.) As I wrote yesterday, there’s no clear trend on the frequency or strength of tornadoes hitting the U.S. It had actually been a historically quiet 12 months for tornadoes until recently. And it’s not clear what, if any, impact warming temperatures are having on tornadoes.

(PHOTOS: Tornado Flattens Oklahoma City Suburb, Kills Dozens)

But according to Peter Hoeppe, the head of the Geo Risks department at the Munich Reinsurance company, damages from tornadoes have been growing over the long term—a trend that’s been driven chiefly by the increase of people and property in vulnerable areas, like the tornado belt. More people in harm’s way mean more people to be harmed when a twister touches down. “This is the major loss driver for both tornadoes and hurricanes,” says Hoeppe.

The population of Oklahoma City increased from around 400,000 in 1980 to nearly 600,000 today, driven in part by the city’s booming, fossil fuel-driven economy. In Moore, a major suburb of Oklahoma City, population has increased by some 57% since 1980, to 55,000 now. That’s a fairly dense for tornado country, which meant a lot of people and property were in the path of the twister on May 20. Just as the rapid growth of population along the coasts has made us more vulnerable to hurricanes and coastal flooding, more people in the tornado belt can multiply the damage done by those twisters

The best way to survive an EF4 or EF5 tornado is in an underground shelter, or in a specially-designed safe room. Cellars would be ideal, but as Megan Garber explains in the Atlantic, the environment in Oklahoma is not:

The relative dearth of storm cellars in Oklahoma comes down, as things so often do, to environmental factors. The soil in the state is composed largely of clay — and that’s particularly true in central Oklahoma, where Moore is located. (“Soils in the Central Rolling Red Prairies,” geologists at Oklahoma State put it (pdf), “are dark and loamy with clayey to loamy subsoils developed on Permian shales, mudstones, sandstones and/or alluvial deposits under tall grasses.”)

Building a private structure and full underground shelter that could withstand a major tornado is certainly possible, but as the economist Kevin Simmons of Austin College told me, “it would be out of the reach of anyone who is not wealthy.” Private safe rooms can be built—Simmons, who lives in tornado country north of Dallas, just put one in his own house for $4,000—but it’s still likely to be out of the reach of a lot of people in Oklahoma.

The state of Oklahoma and the federal government have begun to use financial incentives to encourage more resilient construction in tornado zones. Oklahoma is instituting a lottery to provide people with a maximum rebate of $2,000 to go towards building a tornado safe room, using funds provided by the federal government. More than 10,000 above and below-ground safe rooms have been built so far using that money.

But that funding comes with trade offs. In a 2006 study Simmons co-authored with Daniel Sutter of the University of Texas-Pan American, Simmons found that a program for building safe rooms in permanent dwellings would cost $52 million for every life saved. That “exceeds estimate of the value of a statistical life based on market tradeoffs,” as the authors wrote. (“This is where economists sound horrible,” Simmons notes.) Those figures reflect just how rare tornado fatalities remain today, especially ones that occur to people living in permanent dwellings, which can usually weather the weaker but more common twisters. The chance of death from tornado if you live in a mobile home is 10 times greater, however, since they provide virtually no place to shelter in the event of a twister. Simmons estimates that the cost of saving a life by building a safe rooms for mobile homes—which would most likely take the form of a collective shelter for an entire trailer park—is a comparatively economical $4.8 million. “There may be some good arguments made for some form of public assistance to build community shelters in trailer parks,” says Simmons.

Another place where shelters and safe rooms are important is in schools. Many of the children killed by the Moore tornado were huddling in the Plaza Towers Elementary School, which took a direct hit. On Tuesday Albert Ashwood, the top emergency management official for Oklahoma, told reporters that neither Plaza Towers nor another elementary school in the storm’s path, Briarwood, had safe rooms or basements for students and teachers to take refuge in. Although the state of Oklahoma mandated after the 1999 tornado that all new schools would need to have a safe room, Plaza Towers was built in 1966. We can’t say for sure whether  shelters and safe rooms would have saved the students who died at Plaza Towers—initial reports suggested that the children actually drowned to death—but it should be clear now that public spaces like schools or churches or even highway rest stops can and should have some kind of place where crowds could ride out even the strongest twisters.

The truth is that there’s only so much that can be done to protect vulnerable populations from tornadoes as powerful and as wide as one that tore through Moore. If the death toll remains at 24, the town and Oklahoma may well count itself lucky, as physically devastating as this twister was. Still, we can do more to protect ourselves from nature if we take the initiative. “We will rebuild and we will regain our strength,” Oklahoma Governor Mary Fallin said after surveying the carnage in Moore today. The question is whether we can and will rebuild even better.