Two years ago, more than 200 tornadoes touched down in the Southeast, killing more than 340 people and wreaking millions of dollars in damage. In the tri-state region alone, 81 people died as the twisters devastated communities around Ringgold, Ga.; Trenton, Ga.; Rainsville, Ala.; Apison, Tenn.; Cleveland, Tenn.; and the New Harmony community in Bledsoe County, Tenn.
934 -- Number of debris objects studied.
15 -- Minimum number of tornadoes that carried the debris in the data set.
219 -- Miles traveled by a photo from Phil Campbell, Ala., to Lenoir City, Tenn. The journey broke the previous record for the longest-documented debris trajectory.
Source: Tornado Debris Characteristics and Trajectories During the 27 April 2011 Super Outbreak as Determined by Using Social Media Data.
Tornado debris can't talk.
Wrinkled photographs can't explain how they were torn from albums and sucked into storm clouds. Old receipts can't describe how they soared over miles of countryside until they were dumped into pastures like snow. Quilts can't recount whipping and tumbling on the winds like wild birds.
The debris can't talk, University of Georgia professor Dr. John Knox repeats. But the people on either end of the debris's journey can.
And it's through the unprecedented connection these people have through social media that researchers finally are starting to learn more about those journeys, and what they can teach us.
Two years after the devastating April 27 tornadoes, Knox and a group of researchers published a study that gives a new look at how tornadoes pick up and disperse debris.
It all started with an unlikely scientific data source: Facebook.
An Athens, Ala. woman, Patty Bullion, started the Facebook page, "Pictures and Documents found after the April 27, 2011 Tornadoes," after finding half a dozen windswept photos in her yard. She hoped that someone might recognize the pictures and connect them with their owners.
Within weeks, thousands of people had "liked" the page, and hundreds of photos of recovered items had been posted in albums. Over the course of a year, about 2,000 people had been reconnected with lost belongings.
"I never dreamed it would become what it became," she said. "For some people, it was their only connection back to things they had in their lives before the tornadoes."
Meanwhile, Knox was looking for ways to research the staggering volume of debris that had fallen that day.
"One town after another had been hit, and pieces of them had been strewn all over the Southeast. Everybody had a debris story -- my brother found prescription bottles in his yard in Birmingham."
Studying tornado debris itself is inherently tricky, Knox said. It's like a strange breed of archaeology. By the time the debris is found, the storm is gone. Scientists have to study the objects to try to understand the environment they came from.
And there are plenty of potential pitfalls.
A receipt from a restaurant in Birmingham found in Chattanooga after a storm doesn't necessarily mean that the receipt traveled through the twister.
In the past, Knox said, people who found personal debris in their yard had no real way to trace the items back to their original owners. You might put a little notice in the paper, he said, but that does no good if the items are far from your town.
Knox learned of Bullion's efforts from a newspaper story his father saved. The scope of the project astounded him. Scientists tracking debris usually only had vague and isolated connection points to work with. Here were 2,000 items with personally documented start and an end points.
"We think this is the largest recovery and return project that has ever been done in modern weather disaster history," Knox said. "Patty has done just an amazing work."
He contacted Bullion and asked if it would be OK to use her page for research. She was thrilled.
"He said it was just an incredible data set," she said. "I didn't even realize I was doing that. I never dreamed when we started this it could help with a scientific purpose, too."
Knox pitched what he calls his "harebrained idea" to current and former students, not sure who would be interested.
The room was full for the group's first meeting.
Studying tornadoes is already popular among meteorology students. The social media component added a whole new layer of intrigue, Knox said.
On Saturdays, the students broke into teams and combed through photo albums on the site. They narrowed down the list of 2,000 items, excluding any that had no conclusive takeoff and landing point. That eliminated half of the items, but what remained was still more data than debris researchers had ever had to work with.
They then logged the starting points and ending points of the objects into spreadsheets, then plotted the points on a map. They then connected the dots and overlaid simulated tornado trajectories.
Their findings were jaw-dropping. They tracked dozens of items that had traveled between 130 to 160 miles, and others that reached distances Knox never expected to see.
One photograph was picked up in the storm-ravaged town of Phil Campbell, Ala., and traveled 219 miles to the Knoxville region. The journey broke the previous record for the longest-documented debris flight.
Using the trajectory models, researchers found the debris from different levels of tornadoes landed differently. Debris traveling shorter distances tends to fall 10 degrees to the left of the twister, but farther-flying debris was often dumped back to earth at an angle 5 degrees to the right.
Knox and his colleagues determined that debris picked up by more violent tornadoes traveled farther. The faster winds were more likely to shoot light debris to the tops of the tornadic supercells -- reaching even 20,000 feet -- where they could travel greater distances.
That behavior had never been recorded before.
The findings didn't just satisfy curiosity, Knox said. Knowing more about the angles at which tornadoes disperse debris could be vital for public safety, helping emergency management officials predict where tornado-borne biological or toxic debris may reach.
This could be especially critical in the tri-state region dotted with TVA nuclear plants, Knox said.
The research allows one more view of the tornadoes, one that doesn't focus on all the horror, all of the pain, all of the loss and destruction. It instead tries to dissect the wild mystery of what a tornado is and what it does.
"Hopefully people are seeing this and thinking, 'At least something good is coming out of the suffering,'" said Knox.
THE HUMAN ELEMENT
The researchers' debris maps resonated on a more personal level to Laura Monks, director of the Fayettville, Tenn., branch of Motlow State Community College. The horrific storms out of Mississippi and Alabama dumped a flood of items in the rural area.
"All over people were finding pictures and documents in their fields and pastures," she said. "They didn't know what to do with them."
The college eventually became a collection point for community members who didn't want to directly interact on Bullion's Facebook page.
Monks herself picked up a photo of a man and his dog in Smithville, Miss. Through Facebook, she connected with the man's family and found out that both he and his wife had died. The dog, who disappeared, had shown up at the back stoop of the leveled house a week later.
"It's the positive side that social media can take," Monks said. "The world is a lot closer than we ever really thought."
It's stories like that, Knox said, that brings a uniquely human element to the research. This isn't just science -- it was drawing on social connections and personal stories. Before these photos and quilts and bank statements took the blanket title of "debris," they were carefully framed or folded or filed away in someone's home.
Knox recognized that human element. He encouraged his students not to exploit all the personal details they had access to for the sake of science. They were not to call victims, he directed, or knock on their doors.
"We were aware of the emotional baggage that comes along with something like tornado debris," he said. "This wasn't just a laboratory experiment. This was something that came out of someone's attic and landed in someone's yard."
Contact staff writer Kate Harrison at firstname.lastname@example.org or 423-757-6673.