Sacramento deserves the gold standard of protection.
An excerpt.Can we handle a big flood?
Region should be set for a 500-year event, experts say. It isn't.
By Deb Kollars -- Bee Staff Writer Published 12:01 am PDT Sunday, August 27, 2006
A year after the haunting images of Hurricane Katrina, Sacramento remains at serious risk for a similar disaster.
It is hard to fathom, especially on summer days like these when Sacramento's two rivers, the American and the Sacramento, appear as sparkling ribbons flowing between levees covered in grasses and cottonwood trees.
But the dangers are grave, and solutions elusive.
With the one-year anniversary of Katrina approaching, The Bee asked state and federal hydrologists last week to describe what the water flows and river heights would be if floods of certain magnitudes arrived in Sacramento. It was a departure from the more common practice of talking about floods in terms of their likelihood, such as 100-year events (those with a 1-in-100 chance of happening in any given year.)
The estimates, which engineers dug out of recent and complex hydrological models by the U.S. Army Corps of Engineers, are chilling.
During a 100-year flood, river heights on the American River at Watt Avenue, for example, would reach 49 feet and remain running within the existing 54-foot levees, the models showed.
But the river's height, known as "flood stage," could not even be accurately calculated for larger 200-year events and beyond because the water flows would be so swift and voluminous they would break out levees and gush over the tops, said Dan Tibbitts, a hydraulic engineer with the corps.
"Unfortunately Sacramento is not prepared for these big events," said Arthur Hinojosa, chief of the state Department of Water Resources hydrology branch.
For urban areas, 100-year flood protection is considered the federal government's minimal safety standard. To most flood control experts, it is an inadequate threshold.
It also doesn't exist yet in some of Sacramento's heavily populated areas, including Natomas and the Greenhaven-Pocket neighborhood. Current levee work in Greenhaven-Pocket should provide 100-year protection levels later this winter.
According to the nation's top flood experts, cities such as Sacramento that are vulnerable to flooding should have at least 500-year protection.
If cities settle for less, they may squeak by without consequence for years, decades or longer, said Gerald Galloway, a professor of water resources management at the University of Maryland and one of the nation's pre-eminent flooding authorities.
But rare as they are, a monster flood in Sacramento remains firmly in the realm of possibility, he and others said.
"It's not a question of if. It's a question of when," said Larry Larson, executive director of the American Association of State Floodplain Managers in Madison, Wis.
To reach the 500-year gold standard, Sacramento likely would need to build a dam upstream on the American River, such as the controversial one that has been proposed for years at Auburn, as well as invest billions in other improvements.
