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What is a 500-year flood?

Why are floods happening so often in the St. Louis region?

ST. LOUIS — "It didn't stop, and it just kept coming and coming," Indian Hills resident, Pat Herzing, told 5 On Your Side when asked about Sunday's catastrophic flooding on Mother's Day.

5 On Your Side reporters are hearing flooding descriptions similar to Herzing's more and more. Stories of rapidly rising waters are coming in from all over the Bi-state. 

For at least 10 years, Herzing's neighborhood, Indian Hills, hadn't seen anything like Sunday. 

"I've never seen anything like this before," Herzing said. "I feel like I am on the Titanic."

Sean Stone with MSD Project Clear told 5 On Your Side, "What we had this weekend was a 500-year event."

We've all heard those statistics, but what exactly does it mean for a flood to hit the 500-year marker?

5 On Your Side Weather First Chief Meteorologist Scott Connell said, "500-year flood means the probability in any given year is 1 in 500 that will happen, that's a .2% chance."   

"As climate change and the effects of climate change take hold, we're seeing more frequent and more powerful storms," Stone tells 5 On Your Side. "We're seeing problems in places we've never seen problems before and it's because we're getting amounts of rain we haven't historically gotten before."

Stone followed up by saying this is the second 500-year flood in less than 12 months in the St. Louis region. 

Connell said he agrees, "It's definitely linked to climate change. We know that as the climate warms, the atmosphere can hold more water. That extra water supercharges the atmosphere, so we're going to see heavier rainfall events and we have seen heavier rainfall events over the last 20 years."

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