Surviving the 100-Year Flood Doesn't Mean 99 Years of Safety

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Eleven months ago, Houston had a deadly flood. This week, the city had another.

Events like these are often called “100-year floods,” and that can be misleading. The U.S. government began using the term in the 1960s to describe a flood that has a 1 percent chance of happening in any given year, not a chance of happening only once a century. It’s statistical probability -- and that can change over time.