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SALT LAKE CITY — When you read the term "100-year flood," what comes to mind?
A river on State Street?
A storm of biblical proportion?
An event that won't happen in your lifetime?
A 100-year storm or flood is a statistical term that engineers say is widely misunderstood. A 100-year flood or storm is an event so big that it has a 1 percent chance of happening any given year.
"It's a common misperception that a 100-year storm only happens every 100 years," said Micheal Drake, professional civil engineer with Ward Engineering Group of Salt Lake City.
A 100-year flood or storm is an event so big that it has a 1 percent chance of happening any given year.
"It's not just the general public throwing that term around. Sometimes we've got to beat it out of younger engineers when they come in so people understand what they're talking about."
To help clarify matters, Salt Lake County plans to eliminate the term from its flood control ordinance.
Next week, the Salt Lake County Council will consider an amendment to its flood control ordinance replacing the term 100-year flood to 1 percent annual chance flood.
"The difference is, if you say the 100-year event, people get in their minds that if we have a big flood last year, we've got 100 years before we have another flood," said Scott Baird, director of Salt Lake County's flood control and engineering division.
Related:
How we brought the floods of '83 under control
As I have driven to the freeway, the road takes me above the Jordan River. I recently observed the river at cresting stage. My mind is drawn back to the flood of 1983.Purging 100-year flood from the ordinance will make it consistent with language used by the Federal Emergency Management Administration and other federal agencies, Baird said.
Not only is the term confusing, there is some debate about what a 100-year flood may be.
It's obviously large scale, but were the largest flood or storm events recorded in the Salt Lake Valley the biggest of the big?
"Have we seen the 100-year-flood? We think we did in '83 and '84. What if there's a bigger one?" Baird postulated.
The ordinance change has been placed on the County Council's consent calendar next week.
"It's a nomenclature thing," Baird said. "It's like any of those engineery words. We're just trying to help people understand."
Email:mcortez@ksl.com
