Twenty-five years ago, a massive tornado levelled the North Texas city of Wichita Falls, killing 42 people and injuring 1700.
Walking through tornado-ravaged neighborhoods after a deadly storm 25 years ago, architect Charles F. Harper saw something strange: small closets or bathrooms that seemed to be rising from piles of debris.
In many cases, the center room of a house or business -- even a bank vault -- was the only thing standing after a tornado up to a 1 1/2-mile wide churned through town, hitting 5,000 houses and several apartments. About 20,000 people -- nearly one-fourth of the city's population -- were homeless, while 42 were killed and 1,700 injured.
Harper, who had developed disaster response plans for nearly 10 years for the American Institute of Architects, started studying his town's damage with researchers at Texas Tech University in Lubbock.
What they learned from Wichita Falls sped up the development of "safe rooms" -- center rooms with reinforced walls designed to protect people during storms. Building plans and information about safe rooms are now included in brochures distributed by the Federal Emergency Management Agency.
"That event was unequivocal proof that you could build an structure that could withstand tornado winds," said Chad Morris, associate director of what is now the Wind Science and Engineering Research Center at Texas Tech.
The April 10, 1979, tornado that hit Wichita Falls is the state's fifth deadliest and one of the largest in U.S. history.
On that spring day, three large supercell storms developed, each producing a series of tornadoes that moved quickly across the northern Texas and southern Oklahoma plains.
Some of those twisters killed 11 people in nearby Vernon, one in Harrold and three in Lawton, Okla.
The Wichita Falls tornado stayed on the ground an hour and traveled 47 miles as it wiped out a fifth of the city and damaged even more areas before dissipating in Oklahoma. It is rated an F4, with winds from 207-260 mph.
"I don't know if any tornado in Texas has affected so many people," said Alan Moller, a Fort Worth-based National Weather Service meteorologist who spent a week in Wichita Falls after the tornado. "And we really learned a lot in terms of safety."
Although the mall was heavily damaged, no shoppers died inside. Several who ran to their cars were killed or severely injured.
More than half of those killed, including the girlfriend of Harper's son and her sister, were in cars trying to flee -- believing that buildings were more dangerous -- or were passing through town and had not heard the warnings.
"The big lesson learned was that if you're in a reinforced structure, you need to stay there when a tornado's approaching," Moller said. "Automobiles are a steel death trap in a tornado."
Many people at that time had only seen narrow, funnel-shaped clouds and didn't recognize that the approaching wide, wedge-shaped mass was a tornado, Moller said.
In assessing damage, researchers realized that they had been giving the wrong advice in telling people to open windows as a tornado approached, Harper said. They realized that what blew the roofs off houses was wind getting inside -- and that homes with storm doors and windows or shutters fared better.
"We rewrote the book on what happens in a tornado and how to mitigate damage," said Harper, 74.
Since the tornado, some builders say the demand has increased for safe rooms -- with walls made of concrete blocks or plywood with reinforced steel beams. Buchanan Construction Co. builds safe rooms with 6-inch-thick concrete walls, and only builds concrete houses to meet customers' demands for tornado safety in addition to energy savings, said owner Jay Buchanan.
"I hear more about safe rooms now than I did 20 years ago," Buchanan said.
Today, the town has few reminders of the storm. Near downtown, a memorial park features large sculptures representing crepe myrtle trees that bloomed after the storm and became a symbol of the town's resolve. Another park has a plaque with the names of 45 victims, including three who died of heart attacks right after the storm, and a tree planted for each one.
Even today, the tornado still haunts many.
Dale Sanders, now 56, survived by huddling in her neighbor's cellar with three dozen other people and two dogs. Several men struggled to keep the door closed by clutching the rope.
When Sanders emerged, she didn't recognize her surroundings because houses, street signs, power poles and trees were gone. She saw a dazed man, his arm severed, walking down the street.
"I don't want to remember it," Sanders said. "The only thing I do really is watch for storms, and I do a lot of praying."