The Mississippi River breached more than a dozen levees in the St. Louis, Mo., area Thursday as flooding continued to spread across the Midwest. To mitigate the damage, the U.S. Army Corps of Engineers alone has distributed nearly 13 million sandbags, most of which have been filled and laid down by local residents. Why do we still use sandbags?
Because they're cheap, easy to use, and usually effective. The familiar image of the burlap sack stuffed with sand goes back at least as far as the Revolutionary War—when they were used to build makeshift forts—and they have long been deployed as a defense against deluges like the Great Mississippi Flood of 1927. These days, the bags used to hold back rising floodwaters are more likely to be made of polypropylene plastic, often taken from the scraps of textile manufacturers. They cost about a quarter apiece, and they are packed for delivery by the thousands to flood-stricken areas.
Then locals have to find sand to put in the bags. In Iowa, it has come from local quarries that normally serve as suppliers for construction. Sand has the benefits of being inexpensive, plentiful, and easy for untrained volunteers to handle and clean up. (Clay might be more effective at holding back a flood, but it's more difficult to bag and stack quickly—and to remove when the danger is past.) If for some reason sand weren't available, the Army Corps of Engineers says you could use silt or gravel in an absolute emergency (PDF).
The Mississippi River breached more than a dozen levees in the St. Louis, Mo., area Thursday as flooding continued to spread across the Midwest. To mitigate the damage, the U.S. Army Corps of Engineers alone has distributed nearly 13 million sandbags, most of which have been filled and laid down by local residents. Why do we still use sandbags?
Because they're cheap, easy to use, and usually effective. The familiar image of the burlap sack stuffed with sand goes back at least as far as the Revolutionary War—when they were used to build makeshift forts—and they have long been deployed as a defense against deluges like the Great Mississippi Flood of 1927. These days, the bags used to hold back rising floodwaters are more likely to be made of polypropylene plastic, often taken from the scraps of textile manufacturers. They cost about a quarter apiece, and they are packed for delivery by the thousands to flood-stricken areas.
Then locals have to find sand to put in the bags. In Iowa, it has come from local quarries that normally serve as suppliers for construction. Sand has the benefits of being inexpensive, plentiful, and easy for untrained volunteers to handle and clean up. (Clay might be more effective at holding back a flood, but it's more difficult to bag and stack quickly—and to remove when the danger is past.) If for some reason sand weren't available, the Army Corps of Engineers says you could use silt or gravel in an absolute emergency (PDF).
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