‘500-Year Flood’ Could Happen Again Sooner Than You Think. Here’s Why.

"In the aftermath of Hurricane Harvey, President Trump tweeted that the storm had brought a “once in 500 year flood” to Houston, and expressed support for relief efforts. His words suggested the kind of catastrophic event that hadn’t been seen in the area for five centuries. But parts of Houston saw “500-year flooding” just last year. And in 2001, Tropical Storm Allison also delivered severe flooding to the area.

Harvey has been even more devastating, and officials say the flooding is the worst in state history. But is it really a once-in-500-years event?

Terms like “500-year flood” and “100-year flood” are used as shorthand by government officials and actuaries, but they are misnomers that can confuse the public, said Sandra Knight, a senior research engineer at the University of Maryland and a former official at the Federal Emergency Management Agency."

Nadja Popovich and Claire O'Neill report for the New York Times August 28, 2017.

SEE ALSO:

"Houston Is Experiencing Its Third ‘500-Year’ Flood In 3 Years. How Is That Possible?" (Washington Post)

"Hurricane Harvey Shows How We Underestimate Flooding Risks In Coastal Cities, Scientists Say" (Washington Post)

"Extreme Weather: The Myth Of The 100-Year Flood" (Greenwire)