Ag Today January 12, 2017

Storm surge: Levees under patrol as water problems in Delta grow

Posted Jan 11, 2017 at 8:00 PMUpdated Jan 11, 2017 at 9:25 PM

   By Alex Breitler
Record Staff Writer

Flooding concerns intensified in the the Delta on Wednesday as huge volumes of water surged down creeks and streams into the low-lying river estuary.

Higher than expected water levels had crews patrolling levees and watching carefully for any sign of trouble. An estimated 245,098 cubic feet of water per second was pouring into the Delta, the equivalent of nearly three Olympic-sized swimming pools every second.

And it didn’t end on Wednesday: By high tide late Thursday, the rivers may be even higher as the slug of water from earlier storms passes out to San Francisco Bay.

“When the water’s this high you could have a beaver hole open up and you could have a real problem. You could lose a levee,” said Dante Nomellini, a Stockton attorney who represents Delta farmers.

Century-old Delta levees protect farmland that in some cases is well below sea level. Hundreds of millions of dollars have been spent improving the levees in recent decades, but they still are considered vulnerable to failures that can flood farms, roads and utilities and disrupt the water supply for much of California.

Evidence of the massive flow into the Delta was everywhere on Wednesday. The Calaveras River in Stockton was running high as officials began releasing some water from upstream New Hogan Lake to save room for future storms. Just 13 months ago, New Hogan was a mere 20 percent of average; this week, in a period of two days, it rose from 98 percent to 127 percent of average.

The Stockton Diverting Canal, a normally dry channel built more than a century ago to save Stockton from devastating flooding on the Calaveras, also was running high. Farther downstream, the water inched high enough to inundate the deck behind a home in Riviera Cliffs.

A similar rise was happening, but to a much larger extent, on the Mokelumne River, where the high waters broke through a levee early Wednesday and flooded farmland in south Sacramento County. The Mokelumne may crest even higher early Thursday, about 3 feet lower than its reach during the great floods of 1997.

To the south, the San Joaquin River is expected to continue rising as well, though it has more room to grow within its banks. Projections on Wednesday suggested that the river could rise high enough to cause water to seep onto adjacent farmland.

Bottom line: Just because it’s stopped raining doesn’t mean the flood concerns have evaporated. The National Weather Service’s flood warning, which extends throughout much of the Central Valley, will carry on at least into Thursday.

The San Joaquin County Office of Emergency Services upgraded to a higher alert level on Wednesday, recommending that public agencies be ready to mobilize if a serious flood occurs.

“There’s enough potential,” said Michael Cockrell, the local OES director. “In all four directions of the county, we see flood threats.”

But before all that water can escape toward the bay, it must pass through the Delta, where there has been no major levee failure since the sunny-day Jones Tract collapse in 2004.

Potential threats include wind eroding the sides of the levees and beaver holes that can weaken their integrity, Nomellini said. A sinkhole discovered on Upper Jones Tract on Sunday has been filled and “looks like it’s OK,” he said.

Nomellini said the water levels in Rio Vista on Wednesday appeared to be about 10 inches higher than expected. The tides, runoff from the mountains and barometric pressure are factors, making the actual water level hard to predict.

But it’s not hard to see that the water has gone up progressively since the first major storm on Sunday. Each day, water has spilled higher onto the waterfront promenade in downtown Stockton; on Wednesday even the pedestrian benches were perched in a pool of water.

Members of the California Conservation Corps were dispatched to Twitchell Island, south of Highway 12 in Sacramento County, to put plastic sheeting and sandbags over the levee to protect it from wind-whipped waves.

As Nomellini put it: “We’re keeping our fingers crossed.”