Rebuilding after tornadoes: two designs that could save lives in another storm
More people appear to be looking into safe rooms and monolithic-dome structures to withstand the fierce winds of a tornado and the debris it kicks around.
Following the tornado-driven tragedies that have struck the United States in the past month or more, many survivors are opting to remain and rebuild. They have an opportunity to do so, engineers and emergency managers say, in ways that can dramatically reduce deaths and injuries in the future.Skip to next paragraph
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The opportunities range from installing safe rooms in new and even existing homes to literally thinking outside the box – trading a traditional home design for the graceful curves of a dome.
"If there is a silver lining to this," it's the increased attention that people are paying to safe rooms and other forms of shelter that can help individuals survive even the strongest tornadoes, says Ernst Kiesling, an engineering professor at Texas Tech University in Lubbock who also serves as executive director of the National Storm Shelter Association (NSSA), also based in Lubbock.
For now, however, most of the focus is on surveying the extent of the damage and consoling survivors.
In Joplin, Mo. where an EF-5 tornado – the most powerful category – swept through the city of 50,000 Sunday, at least 125 people were killed. It was the deadliest tornado since modern record keeping began in 1950, according to the National Oceanic and Atmospheric Administration (NOAA). Some 900 people have been injured, officials say, and 230 more have been reported as missing.
Meanwhile, cleanup began Thursday following another spate of tornadoes of varying intensities that touched down Wednesday in Texas, Mississippi, Louisiana, Tennessee, Arkansas, Missouri, Iowa, Oklahoma, Indiana, Illinois, and Ohio.
Even California failed to escape the day unscathed. At least two tornadoes – and perhaps as many as four – reportedly touched down near Chico, along the foothills of the Sierra Nevada mountains north of Sacramento.
So far, no fatalities have been reported from Wednesday's activity.
To be sure, Greensburg's experience is atypical in some significant ways, notes Casey Cassias, director of practice for BNIM, an architectural firm based in Kansas City, Mo., that worked with Greensburg to develop a master plan for its reconstruction.
Greensburg, a small farming community in south-central Kansas, was essentially erased from the map by a tornado in May 2007. As the community regrouped and began to map out its future, one thing that residents wanted was a town would meet the highest standards for energy use and efficiency set by the US Green Building Council in Washington.
In addition, Mr. Cassias says, designs for public buildings such as the local high school, as well as individual homes, included adequately hardened rooms to serve as storm shelters. In some cases, people who replaced their homes put a second or third bedroom with all the amenities in the basement – but hardened so that if severe weather threatened overnight, the owners could go to bed in the basement room and not have to worry about sleeping through a distant warning siren.
Hardened safe rooms of eight square feet – built as a pantry or small bathroom as part of a house under construction – can cost between $6,500 to $8,500, according to estimates by the Federal Emergency Management Agency (FEMA). Refitting an existing house can boost that cost to between $8,000 and $10,000, the agency estimates.
While there has been some disagreement among weather forecasters and engineers over how intense a tornado these shelters can withstand, evidence over the past month is suggesting that even above ground on the first floor, a properly designed and installed safe room can withstand winds of 250 miles an hour or more and the debris that such winds generate.
Even owners of mobile homes, the most vulnerable structures, can install prefabricated underground storm shelters just outside the homes at costs that can be as low as $5,000 if federal grant money is used to offset the cost, according to FEMA.
Another approach that appears to be gathering interest involves building a concrete dome that is anchored to a concrete base.
Such monolithic-dome structures "are the lowest cost option for creating windstorm-protected space" above ground, says Gregory Pekar, state hazard mitigation officer in the Texas Department of Public Safety's division of emergency management. The structures can withstand winds above 200 miles an hour as well as wind-driven debris.
Monolithic domes have cropped up across the country as church sanctuaries, school gymnasiums, and other public buildings, which then double as community storm shelters.
The domes can be configured as one- and two-story homes, adds David South, widely acknowledged as the pioneer in building concrete monolithic domes.
On Tuesday, a strong tornado hit Blanchard, Okla., and delivered a direct hit to a monolithic-dome home outside town. Photos that Mr. South supplied of the home's exterior show a landscape devoid of treetops, with a car shoved up against the structure. The home's windows are blown out, the interior a shamble, but the dome is still standing, even if it has large dings on the outside.
True, monolithic-dome shelters, let alone entire houses, may be a tough sell in many communities, Mr. Pekar acknowledges. "If money is tight and your population will accept it, go with a dome safe room" outside, he says.
Dr. Kielsing of Texas Tech is more cautious about endorsing any specific implementation of a monolithic dome. In principle the idea is sound, he says, because the shape presents much less wind resistance to an oncoming twister than does a box-style building. But so far, none of the handful of companies building dome shelters has sought certification from the NSSA, although people building them as emergency shelters have received FEMA money to help pay for construction.
Steel and concrete, while important for reducing fatalities and injuries during tornadoes and hurricanes, represent only part of a stricken community's opportunity for rebirth, notes Cassias of the architectural firm BNIM.
One additional lesson from Greensburg was the power of the survivors coming together after the disaster to lay out a common vision for their community. "That sense of community born of a shared experience" helped reconstruction plans progress, he says.
But it also was important for residents to realize they couldn't turn back the clock, as potentially comforting as that thought might be.
In one sense, this was somewhat easier to achieve in Greensburg because the entire physical slate was wiped clean. "Even in Greensburg at some level, there was a longing by a lot of those folks to go back to the way it was five minutes before the tornado," Cassias says.
"It will never quite be the same, so what is it that you want to create going forward?" he asks. "Greensburg embraced it as an opportunity" to rethink, re-envision the town.