Water & Drought

After years of drought, Sacramento confronts an old foe: Flood risk

Aerial views of Sacramento area flooding

Bee photographer Randy Pench flew in a helicopter on Thursday, Jan. 12, 2017 to document the vast flooding that has occurred over the past week. The views are stunning.
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Bee photographer Randy Pench flew in a helicopter on Thursday, Jan. 12, 2017 to document the vast flooding that has occurred over the past week. The views are stunning.

In the years before California’s drought, it wasn’t unusual for Sacramentans to spend winters worrying about floods. After more than five years with little rain, the past two weeks delivered a bracing reminder that the region remains vulnerable to rising waters and overtopped levees.

The recent rainstorms flooded scattered sections of greater Sacramento, from the Garden Highway north of downtown to the rural communities south of Elk Grove. Three small levee breaches added to the havoc caused by the wayward Cosumnes River. The Sacramento Weir, a flood-release valve used to flush excess water from the Sacramento River system into the Yolo Bypass floodplain, had to be opened for the first time in a decade.

For all that, however, the recent storms produced river flows that were only a fraction of what’s possible in the region. The Sacramento and American rivers largely behaved themselves and remained several feet below flood stage. For the most part, the city escaped street flooding that often accompanies major storms. In contrast with Northern California’s last great flood, in 1997, the big reservoirs such as Folsom Lake were comparatively empty, able to accommodate big rainfall without a threat to dam safety. Federal officials tend to keep the lake at a lower level today than in 1997 to make room for floodwaters.

“It was a moderate test,” said Joe Countryman, a member of the Central Valley Flood Protection Board and a former engineer with the U.S. Army Corps of Engineers. “It wasn’t the big one. It was more than moderate in terms of our typical storms, but … it wasn’t a big threat.”

Which is exactly why Countryman and other flood-safety experts are still anxious about Sacramento’s chances of falling victim to a major flood.

Often described as the U.S. metropolitan area at second-greatest risk of a devastating flood, after New Orleans, the Sacramento region has spent about $2 billion over the past 20 years in a concerted effort to fortify its defenses. It has strengthened levees on the Sacramento and American rivers and south-county streams, and has addressed problems in such vulnerable areas as Arcade Creek, the Pocket and Natomas. It’s about to finish a new spillway at Folsom Lake that will enable reservoir operators to release more water into the American River as big storms approach.

Yet Sacramento’s flood-safety work is far from complete. The Sacramento Area Flood Control Agency says much of the region still lacks 100-year-flood protection – that is, the ability to withstand high river flows and flood conditions that have a 1 percent chance of occurring in a given year. Property owners in areas without 100-year protection are generally required to buy flood insurance.

Rick Johnson, SAFCA’s executive director, said $2.4 billion worth of flood-control projects are still on the drawing boards. They include plans to widen the Sacramento Weir and Yolo Bypass, to address lingering levee problems on the major rivers and to complete repairs to the levees ringing the Natomas basin, whose vulnerabilities prompted the city to halt new construction from 2008 to 2015.

Once completed, Johnson said the projects on Sacramento’s to-do list should enable the region to handle a 200-year flood – the standard for urban areas established by the Legislature in 2007. But getting there will take several years and will depend in part on Congress’ willingness to appropriate federal dollars for various projects.

In the meantime, area officials look to the skies and hope the region’s infrastructure can hold up.

Take the city of Sacramento. It spent $150 million on flood safety over the past 15 years. Most of the money was spent on detention basins to store excess water, and to upgrade pumping stations that keep water flowing through underground pipes instead of pooling on city streets.

Those projects have helped with street flooding and other problems, but the city needs to spend another $300 million or more to achieve truly reliable flood protection, said Utilities Director Bill Busath.

“Sixty percent of our system is not ready for a 100-year storm,” Busath said. “We’re not complacent, but right now we don’t have money for capital improvements.”

If even just a 20-year storm were to hit, “we are going to have a lot of flooding,” he said. A 20-year storm has a 5 percent chance of occurring in a year.

Despite five-plus years of drought, flood risks are part of the Sacramento landscape. It’s not just one big storm that could bring disaster. It could be a succession of heavy rains, mixed with warm temperatures that produce massive Sierra snowmelt. The monstrous Northern California storms of 1986 and 1997 pushed the region’s levees to the max.

Sacramento County’s population has grown by 300,000 since the 1997 flood, putting more people at risk. Area officials say shoring up levees and making other improvements are simply the price of living in Sacramento.

“Between the rivers and the (Yolo) Bypass, we’re completely surrounded by levees, and we’re all in this single flood basin,” said West Sacramento Mayor Christopher Cabaldon, whose city is in the midst of $1.5 billion worth of levee improvements. “It’s been particularly important for us. We can’t just abandon a part of our city and go somewhere else.”

Sometimes the threat level can surprise, even in a flood-saavy community such as Sacramento.

In 2008, the Federal Emergency Management Agency made a startling announcement: Based on stricter post-Hurricane Katrina standards, the levees guarding Natomas lacked the minimal 100-year-flood protection. FEMA said new buildings had to be raised as much as 20 feet to meet agency rules.

As a result, the city imposed a building moratorium in Natomas, and SAFCA partnered with state and federal authorities to improve the levees. By late 2012, after $450 million had been spent, 18 of the 42 miles of suspect levees surrounding Natomas had been fixed.

The work wasn’t enough to deliver 100-year-flood protection, but it was sufficient to enable the city to lift the Natomas moratorium in 2015.

“We’ve completed the 18 worst miles,” Johnson said.

The Army Corps of Engineers is expected to begin work on the remaining 24 miles this year. But completion could take several years and is subject to Congress appropriating the dollars to keep the $750 million project on track. As it is, the work has been delayed for several years because of funding problems.

Most projects are funded by a mix of state, federal and local dollars, and Sacramentans have shown a willingness to tax themselves when it comes to flood control. Last summer, Sacramento-area property owners voted to let SAFCA increase annual homeowner fees by an average of $42 a year, to a total of $99. The vote will raise an additional $250 million for SAFCA-funded projects over the next 30 years.

All told, Johnson said, he hopes to achieve 200-year-flood protection for Sacramento in time to meet a 2025 deadline set by the Legislature. Otherwise, Sacramento could face a fresh round of building restrictions.

SAFCA, though, wants to go further. The Army Corps of Engineers is planning to raise Folsom Dam by about 3 1/2 feet sometime over the next several years. Johnson said the project would increase the reservoir’s flood capacity by up to 50,000 acre-feet.

That project, along with a planned widening of the Sacramento Weir and Yolo Bypass, should give the region 300-year-flood protection, Johnson said. That’s significantly higher than the Legislature’s 200-year mandate.

Why the extra protection? Johnson said the additional comfort level could become a necessity, not a luxury. As climate change worsens, the winters will turn warmer and more of the precipitation will fall as rain instead of snow, bringing heavier volumes of water cascading into the Valley from the Sierra Nevada.

“With climate change, we’re seeing more extreme events,” Johnson said. “The same snowpack 30 years ago was melting in the spring – now it’s melting earlier.”

Dale Kasler: 916-321-1066, @dakasler

Map of Sacramento flood-control projects