Skip to main content
U.S. flag

An official website of the United States government

We had a "100-year flood" two years in a row. How can that be?

The term "100-year flood" is used to describe the recurrence interval of floods. The 100-year recurrence interval means that a flood of that magnitude has a one percent chance of occurring in any given year. In other words, the chances that a river will flow as high as the 100-year flood stage this year is 1 in 100. Statistically, each year begins with the same 1-percent chance that a 100-year event will occur.

Learn more: