How Sandbags Work

Why Sandbags?

Uncontrolled floodwaters in the American Midwest.
© Campbell

People have used sandbags for several hundred years, going back as far as the Revolutionary War [source: Leibenluft]. With science advancing in so many areas, why do we still use this low-tech solution to control floodwaters? Here are three simple reasons:

First, sandbags are easy to use. To prepare sandbags, it only takes a few volunteers with shovels, gloves and some knowledge of safety precautions. When a flood is impending, everyone has to work fast, so you don't have the opportunity to bring in experts and engineers, let them scratch their chins and figure out the best thing to do. You need quick action; you want all hands on deck and supplies that are easy to get. It's hard work to make sandbags, but it's not rocket science.

Second, sandbags are inexpensive. The bags and the sand are cheap to buy, so most people can use these. You can buy the actual bags in quantities ranging from 10 to thousands per box. The average person who is about to be knee-deep in water in his or her living room may not have thought to order sandbags in advance, but this isn't a cause for concern. You'll find the bags at a Home Depot or any similar type of store. For example, you can get 500 sandbags at a Home Depot for $179, or 36 cents a bag [source: Home Depot]. When you go to buy your sand, ideally, you want to buy a coarse-grained type of sand. Think of sandbox or playground sand as high quality and scale down from there. If you need a better guideline, try this one: Unused sand from sandbags ends up in gardens as soil or fill. People also save it to sand icy roads in wintertime. That's the kind of sand you're looking for; however, in an emergency, sand is sand. Use what's available.

Third, sandbags work. They've been working for years, and if it's not broken, don't fix it. So now we know why we rely on sandbags, but how do they work?