The sky is ominous. Programing for the evening is preempted. Screens are filled with maps with bright colors and directional tracks and forecasters are relaying watches and warnings and calling for neighborhood after neighborhood to “take shelter immediately!”
It’s tornado season.
I’ve spent most of my life in the north, where storm planning consisted of gathering provisions, gassing up the snow blower, and hunkering down until the worst was over. I always knew that we might be inconvenienced, but my family would be safe. As I sit in my Cornelius home with tornado watches in the air, I don’t have that sense of security. I’ve seen too many photos of concrete slabs wiped clean and homes made into match sticks.
Knowing that I needed more information, I got in touch with some experts, and what I learned made be feel better. So for this column, I want to share that information with you.
Professor Tom Schmidlin of Kent State University conducts studies on responses to tornadoes and the social aspects of tornadoes, such as the risk of death. I asked him how concerned we should be with tornado season already underway. He started by putting the overall risk in perspective.
“The chance of a home being hit by a tornado is very small and the chance of EF-5 damage (the most deadly) at a home is very, very small,” he said.
A look at the data confirms what he says. Between 1991 and 2010, North Carolina averaged 31 tornadoes per year. In Cornelius, the risk of earthquakes is higher than the risk of tornadoes, and both are much lower than the national average. See the chart for risk scores:
Even more comforting is the fact that most tornadoes are of low intensity. Using the scale developed by professor T. Theodore Fujita in 1971 and modified in 2007, the most deadly tornadoes – those ranked EF-3 through EF-5 – account for just 26 percent of the storms (and 67 percent of storm-related deaths). But, North Carolina is outside the core of high-risk states. On average, an EF-3 through EF-5 tornado will strike the state just once every two years. As Professor Schmidlin suggests, it may be many years before a tornado of any strength would strike anywhere close to our homes.
INTERIOR ROOM OR SEPARATE SHELTER?
I asked Professor Schmidlin if the conventional wisdom of sheltering in an interior room was still valid advice.
“The ideal answer is to build a safe room or a small underground tornado shelter, either under the slab or outdoors near the home,” he said. “If a person feels unsafe in their home, they could identify a sturdier building nearby that will be open and available as a shelter. This would not include retail stores, gas stations, or convenience stores, but some government buildings are probably stronger than a house.”
I asked Cornelius officials about opening government buildings as storm shelters, but they said they don’t want people on the roads in the face of a tornado, and would prefer they seek shelter at home. They did agree that a study of the options was necessary, however.
With well-constructed storm shelters heading the FEMA storm protection options, I contacted Ernst Kiesling, Professor of Civil Engineering at Texas Tech University and Executive Director of the National Storm Shelter Association. His response was clear: build a shelter.
“There are well established standards (ICC 500) and guidelines (FEMA 320 and 361) for storm shelters that offer a very high degree of protection from the most extreme windstorms,” Professor Kiesling said. “The design criteria and the designs in these publications lead to the peace of mind of knowing that a safe place is available. Most other strategies leave uneasiness as to the severity of the storm and many, many ‘what if’ questions.”
SHELTER: TO BUILD OR NOT TO BUILD?
Professor Kiesling is right. A sturdy timber and metal shelter can be built in a home for about $2,500. A commercial shelter with plywood and Kevlar starts at about $6,000. There are photos of a DuPont Kevlar shelter standing in the wreckage of Joplin and it is clearly impressive protection.
But here’s another point to consider: even though tornadoes are scary, few people will die in one. Your odds of a tornado death are 1 in 60,000. Dying in an air crash has odds of 1 in 20,000. Falling down kills 1 in 246. Perhaps it’s better to spend $2,000 to fall-proof your home than on a storm shelter.
Many of us simply do not have the space to build a shelter either in or under our home or in the back yard. We need a practical, cost-effective answer to the sheltering question.
Professor Schmidlin offered this advice:
“I think the best advice is still the standard—get into a small, interior room without windows, wear a helmet, cover up with blankets. Wear sturdy shoes, take work gloves, and keep your phone with you.”
When pressed, storm shelter expert Professor Kiesling gave similar advice.
“I would suggest taking refuge in the most central part of the lowest level of the house. Put as many walls between you and the outdoors as possible. A small room such as a closet, under a stairway, pantry or bathroom has more inherent stiffness and strength due to the higher concentration of structural members. Stay away from windows and the fall radius of chimneys, most of which are not reinforced. If heavy furniture is available, get under it.”
FEMA—The Federal Emergency Management Agency—concurs in this advice and adds the following tips for homeowners:
- Most injuries come from flying debris so protect the head.
- Do not open windows. The storm may take them out anyway, but keep the envelop closed as long as you can.
- Leave a mobile home or vehicle for better shelter. If none is available, lie flat in a depression or ditch, not under an overpass or bridge.
- Since half of all tornado injuries occur after the storm has passed, watch for nails and sharp debris, unstable structures, broken gas lines and exposed electrical lines.
There is much more information available on-line. If you want to build a shelter or just have better information to deal with the storm, see the following sources.
CDC Emergency Preparedness and Response—Tornado page at http://emergency.cdc.gov/disasters/tornadoes/prepared.asp
Texas Tech Wind Science and Engineering Research Center (WiSE) http://www.depts.ttu.edu/weweb/
FEMA Tornado Preparedness at http://www.ready.gov/tornadoes
Tornado Protection: Selecting Refuge Area in Buildings. FEMA P-431. Design details for engineers and architects for tornado protection, http://www.fema.gov/library/viewRecord.do?id=1563
Build A Safe Room
- Taking Shelter from the Storm: Building a Safe Room Inside Your House. FEMA L-233. Brochure providing details about obtaining information about how to build a wind-safe room to withstand tornado, hurricane and other high winds.
- Taking Shelter from the Storm: Building a Safe Room Inside Your House. FEMA L-320. Manual with detailed information about how to build a wind-safe room to withstand tornado, hurricane and other high winds.
DuPont Storm Room with Kevlar at http://www.stormsolutions.us/stormrooms.html