And that is the downside of relying on levees (stretched out for miles) for primary flood protection, and the reason most prefer relying on dams (centrally located) instead.
With levees, the ongoing maintenance, which the Sacramento region has largely neglected, is crucial.
An excerpt.
Natomas levee to get quick fix-up
Weakened by a pipe deep within, a levee section is seeping and could fail.
By Deb Kollars - Bee Staff Writer Published 12:00 am PDT Saturday, October 14, 2006
A deteriorating section of levee that poses a serious flood risk to the Natomas community will get an emergency fix starting this month before the rainy season arrives.
But it will have to wait until next year or longer for a more thorough repair.
The site is on the east side of the Sacramento River, just south of the Sacramento-Sutter county line. It has a different -- and more unsettling -- story than many other levee locations receiving emergency repairs this summer and fall. Most are straightforward erosion sites, eaten away by fast, high flows on the river.
This one has problems from deep within. And possibly long ago.
"It's our most vulnerable spot in Natomas right now," said Paul Devereux, general manager of RD 1000, the reclamation district that maintains levees surrounding Natomas. During high water levels, a levee break at the site would inundate thousands of homes in Natomas neighborhoods within a day or so, he said.
On Friday, bids were opened for the emergency installation of a metal sheet pile wall to reduce the threat of seepage and foundation failure this winter. RD 1000 trustees meet Wednesday to award a contract.
The problems at the site -- which Devereux and others believe are tied to an old pumping station that operated next to the levee since 1920 -- made a disturbing appearance during the New Year's storms 10 months ago.
As rains pounded and river levels rose, water and sand and soil started bubbling up in "boils" near the pumping station. It was a bad sign: River water was traveling under the levee and bringing soil with it. Crews struggled to control the seepage with sandbags.
Left unchecked, such seepage patterns can cause levees to cave in and fail, said Rod Mayer, chief of the state Department of Water Resources flood management division.
