As Hurricane Sandy swept toward the U.S. in October 2012, residents on the East Coast scrambled to prepare. People filled burlap sacks with sand and piled them in front of their homes and businesses. They hoped that when the storm surge flooded the coast, the sandbags would hold back the seawater that threatened to destroy their property.
Peyton Robertson, who was a fifth-grader at the time, listened to the news reports. The hurricane flooded parts of the coast in his hometown of Fort Lauderdale, Florida. Farther north, the monster storm slammed other coastal states.
A record-high storm surge engulfed low-lying parts of New York City. The storm killed more than 70 people in the U.S. alone, forced tens of thousands to evacuate, and caused billions of dollars worth of damage.
The disaster got Peyton thinking about ways to hold back floods—specifically saltwater—during hurricanes. He came up with an invention that earned him the title of America’s 2013 Top Young Scientist—and his creation could someday protect lives and property.
SWAMPED BY SEAWATER
Hurricanes are nothing new to Peyton. When he was 4 years old, he and his parents took shelter in a closet as the winds of Hurricane Wilma screamed around their house.
“In my home state of Florida, we are all keenly aware of how devastating saltwater floods can be,” he says. The salt from seawater reacts with building materials such as concrete and metal. If people don’t clean away the salt quickly, it can corrode buildings, sidewalks, and electrical systems long after the floodwaters have receded.
To hold back storm surges, engineers design defenses such as seawalls. According to Kristin Mazur, a civil engineer with the U.S. Army Corps of Engineers, such preventive measures are the best way to reduce flood damage. But when a really powerful hurricane strikes, the usual defenses may not be enough.
That’s when emergency crews turn to a common, last-ditch effort to protect against floods: filling sandbags to create a temporary barrier. As Hurricane Sandy approached Virginia, where Mazur works, she and others from the Army Corps of Engineers rushed into action. “We piled up as many sandbags around the most vulnerable areas of the state as we possibly could,” she says.
Sandbags have pros and cons. “They’re inexpensive, and they’re easy to make—but they are heavy,” says Mazur. Moving bulky sandbags into place is hard, slow work that carries the risk of injury.
HOLD THE SAND
Peyton’s idea was to replace heavy sandbags with lightweight, reusable bags that contained something other than sand. When he started to research the idea, he found that sandless sandbags already existed. He learned that they contained a polymer—a substance made of small molecules linked together in a repeating structure—that expands as it soaks up water.
But Peyton wanted to design a bag specifically to fight saltwater flooding. He knew that to form the most stable barrier, the bags had to weigh more than the saltwater pushing against them. “My idea,” he says, “was to add salt to the polymer to make it heavier than approaching seawater.”
That presented a big challenge. “When you add salt to expandable polymer, the polymer swells less,” he says. Through numerous calculations and trial and error, Peyton figured out the right amount of salt to add to the bags.
“Once they fill with water and the polymer expands,” he says, “the bags have a salt content three times greater than seawater.” Since each bag is heavier than the same volume of seawater, it won’t wash away during a flood.
Peyton also designed fasteners so that the bags would interlock to form a stronger barricade. Then he made a video about his invention and entered it in the Discovery Education 3M Young Scientist Challenge, a competition for students in grades 5 to 8.
TESTING AND TWEAKING
In June 2013, Peyton got a call telling him that he was a finalist. He would have three months to tweak his invention before presenting it to the judges in person.
Each finalist was assigned a scientist as a mentor. Peyton discussed ideas with his mentor by phone and improved his prototype. He tested each design against traditional sandbags. Some of his tests failed, but he viewed each failure as progress, since it showed him what didn’t work and gave him new ideas to try. “In a football or basketball game, time runs out,” Peyton says. “But when you are working on something and it doesn’t work, you just extend the game and give your experiment or prototype another go.”
Last fall, Peyton traveled to Minnesota for the final competition. He showed the judges his prototype, which lies flat and weighs only 1.8 kilograms (4 pounds) when dry but is more than 13.6 kg (30 lbs) when it soaks up water and expands. Unlike conventional sandbags, Peyton’s bags mold against each other as they expand, so there are no gaps between them. And the polymer and salt dry and return to their normal state after a flood, so the bags can be reused.
The judges awarded Peyton the top prize—$25,000 and the title of America’s Top Young Scientist. He and three other finalists won a trip to Costa Rica. Peyton advises other student inventors to start looking for solutions to problems close to home. For instance, he’s now thinking about ways he might be able to protect citrus trees from disease and help stranded whales find their way back to sea—both are issues he’s learned about by watching the local news in Florida.