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A Decade of Flood Engineering in Napa Awaits Test From Nature

| November 30, 2012
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The Napa River has flooded downtown Napa 21 times during the last century. The last severe event was in 2005. (Photo: Craig Miller)

When this kind of “atmospheric river” bears down on the North Bay, folks in downtown Napa keep one eye on the sky and the other on the historically mischievous river that loops through the middle of town. With 21 “serious” floods in the past century, it’s hard to blame them.

City and county engineers are also sizing up Napa Creek, which flows into the river near downtown. It was barely a babbling brook as the second of three storms approached this week — but looks can be deceiving.

“It’s a flashy creek,”says Julie Blue Lucido, Napa County’s flood project manager, who was out inspecting a new set of debris gates and bypasses designed to keep the creek tamed. “It’s a small watershed, so when the rain comes, the creek responds very quickly. It can rise in a matter of hours multiple, multiple feet.”

And indeed, where the creek looked like a laughable threat on Thursday, it had risen markedly by Friday morning, though it remained below the 10.5-foot flood level. Flood managers are also starting to show concern that at the rate it’s rising, the much larger Napa River could reach flood stage sometime this weekend. The river forms an “oxbow” and has had an irritating tendency to take a shortcut through downtown when the waters rise enough. On Friday morning, the river had risen to more than 18 feet at a key measuring point. Flood stage is at 25.

City and county engineers inspect flood control structures on Napa Creek on Thursday. Workers have terraced the creek banks and added the gated bypass seen in the background, roughly doubling the carrying capacity of the creek. (Photo: Craig Miller)

Folks in Napa have been preparing for this week for nearly 15 years. Since 1998, residents have been paying an extra half-cent on the sales tax to fund just part of the county’s half-billion-dollar flood control project. The rest has come in fits and starts from Washington. But it was hard to find people downtown this week who didn’t consider it worthwhile.

“Anything to keep the flooding down is definitely going to help,” said Rick Garcia, who works downtown selling auto warranties. “I can’t miss the time if my business closes.”

Among other measures, engineers have raised or replaced seven bridges, demolished homes and businesses in the floodplain and by creating more than 900 acres of wetlands and terraces, given the river a place to flood naturally when it needs to. But the job still isn’t finished — and isn’t likely to be for another six years.

“The flood protection isn’t in place until that whole system is in place,” Lucido told me. “We’re making progress but until those last features are done, we’re still a community at risk here,” she said.

Friday morning seemed to confirm that assessment. On Thursday, after the first storm had passed, people were hoping this atmospheric river wouldn’t provide a premature test of the engineering, though it’s looking more and more like it might.

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Category: Napa, Natural Disasters, Water

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About the Author ()

Craig is KQED's science editor, specializing in weather, climate, water & energy issues, with a little seismology thrown in just to shake things up. Prior to his current position, he launched and led the station's award-winning multimedia project, Climate Watch. Craig is also an accomplished writer/producer of television documentaries, with a focus on natural resource issues. Reach Craig Miller at cmiller@kqed.org.

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