National Geographic : 2009 May
PHOTO: REBECCA HALE, NG STAFF. SOURCE: NYP CORP. TECHNOLOGY Sandbagged For centuries sandbags have stopped floods. They can fill in a divot in a dike or stand tall on uneven terrain. But hundreds of volunteers are needed to fill the bags---sometimes funneling sand through an upside-down traffic cone---and to schlep them to build walls. Inventors are devising more efficient devices: plastic modules filled with sand by a front loader, rubber tubes pumped full of water to weigh them down. Don Ward tests these higher-tech options for the U.S. Army Corps of Engineers and says they work well. "I'm amazed we still use sandbags," he adds. So why do we? Officials may balk at buying new equipment in advance of a flood. When a deluge does loom, they turn to the familiar. "People trust sandbags," says James Blatz, a University of Manitoba engineer. Last June, Mayor Jo Anne Smiley led the effort to fill a million bags with 9,000 tons of sand to save Clarksville, Missouri, population 490, from the raging Mississippi. Says Smiley, "We did not lose one thing we sandbagged." ---Marc Silver BAGS BY THE NUMBERS The versatile sandbag stops bullets, props up road signs, and holds back floodwaters. ■ Some 14 million were deployed on the Mississippi River for the floods of 2008. ■ 27 cents is the average price tag of a single bag. ■30to40poundsisthe ideal weight of a sandbag. ■ 3 inches of shrinkage per 4 feet of height typically occurs during a flood. Burlap Post-flood, the fiber degrades in weeks. Green For military uses, a blend-in color is best. Orange The bright hue stands out on road barriers.