The U.S. Army Corps of Engineers has withdrawn its endorsement of levees protecting parts of Sacramento, reversing a 1998 evaluation that has facilitated a construction boom in the Natomas area.
In a letter released Tuesday to The Associated Press, the Corps’ chief engineer in Sacramento attributed the decision to local and federal studies that have unearthed levee vulnerabilities.
“Based on this information, we can no longer support our original position regarding certification of the levee system surrounding the Natomas area,” wrote Thomas E. Trainer, chief of the engineering division.
The letter was forwarded to the Federal Emergency Management Agency, which certified the Natomas levees in light of the Corps’ 1998 finding the levees provided 100-year flood protection.
The certification led to skyrocketing development of the Natomas area — a section of the state capital north of downtown that flood experts now say could be submerged by at least 13 feet of water if the levees failed.
An area with 100-year protection has a one chance in 100 of flooding in any given year.
If Natomas were to lose its 100-year designation, flood insurance would become mandatory for people with federally insured mortgages, insurance rates would increase, and building restrictions could be implemented.
But local officials described the Corps letter as an expected formality, which they have been told should not change FEMA’s current assessment of Natomas.
That’s because the Sacramento Area Flood Control Agency, which commissioned a March study that first identified the gapping weaknesses in the levees, has already begun a $370 million project to upgrade the system to 200-year flood protection. That is twice the protection required by FEMA.
“We’re not going to wait for FEMA to act, we’re got to act to resolve this,” said Pete Ghelfi, director of engineering for the Sacramento flood agency.
He said construction should begin next year to fortify the Natomas levees over the next five years.
In total, 20 of the 26 miles of levees surrounding Natomas need some kind of work, including erosion protection, deeper walls to prevent seepage and greater height to withstand bigger floods.
FEMA spokeswoman Kim Walz confirmed that the agency would not re-evaluate the Natomas area if Sacramento officials fix the levee problem.
Jeffrey Mount, a professor at the University of California, Davis, said local planners now face a real decision about whether to temporarily curb construction behind levees that will not be strengthened for another five years.
“The politically difficult question is whether you continue to put people at risk,” Mount said. “Is there the political will to halt development out on the flood plain until they’ve got this worked out?”
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