The Bottom Drops Out: The Delta's Sinking Islands | KCET
The Bottom Drops Out: The Delta's Sinking Islands
An explanatory series focusing on one of the most complex issues facing California: water sharing. And at its core is the Sacramento-San Joaquin Bay Delta. Stay with kcet.org/baydelta for all the project's stories.
"It's the worst damn mess I've ever seen, and I've seen some pretty bad ones."
When the Contra Costa Times captured that January 2011 remark from retired UC Berkeley engineer Robert Bea about the safety of the levee system dividing land from water in the 738,000-acres that make up Sacramento-San Joaquin Bay Delta, things were in much the same shape they are now -- except wetter. Four years ago, thanks to a freakishly wet December in 2010, if the Delta's levees had failed, there may have been just enough water in California's elaborate and attenuated storage system to weather collapse of its most important north-south transfer point until Delta levee repairs were done.
Today, the worst damn mess that the man who also worked on the Exxon Valdez, Deepwater Horizon, and Katrina disasters has ever seen is drier. The Delta still has its same mix of precariously sited gas works, power lines, highways, cities, shipping lanes, and farms. But prolonged drought has reduced reservoir storage of Delta water up and down the state's supply line to crisis levels. Meanwhile, smack in the Delta, at the crux between the winter snow-capped mountains that supply our water and lowland water export canals, only a network of more than 1,000 miles of levees protect that water from being lost or fouled as it is lifted from the estuary into export canals. And the ground supporting many of those levees is sinking.
Descendants of the farmers who drained the Delta's wetlands and built those dikes to protect their fields over the last century insist that their levees are fine. Meanwhile, scientists say that the very same levees amount to a disaster in waiting. It is their warnings about the combined threat of rising seas and sinking land beneath the levee footings that are at the heart of Governor Brown's push to build a multi-billion dollar pair of tunnels to carry the exporters' share of the Sacramento River's water under the Delta rather than allow it to follow its more natural path through it.
A previous installment of this series explained how what was originally intended in the 1930s as temporary use of the Bay Delta's wetland canal system as a default distribution hub of California's water delivery system became the standing arrangement. This article looks at why that leaves California's north-south aqueduct system hinged on its weakest link.
The short answer: the Delta lacks adequate terra firma. "This is a landscape that evolved over 10,000 years as sea level rose after melting of continental glaciers," explains geologist Jeffrey Mount, founding director of UC Davis's Center for Watershed Sciences. "The marsh that established kept up with sea level rise. It was growing tules, these tules would fall over and die and new tules would grow on top of it. Basically that's how it formed the peat soil. So you've got this wedge-shaped deposit that tends to be thickest in the middle of the Delta and then thins as it gets to the side."
As pioneer farmers steadily drained the tule wetlands and formed the diked farm tracts intersected by the Delta's canal system, the planting, burning, and tilling of the peat fields caused the soil to oxidize. "The land elevation has been lowered for a century," says Mount. "And that elevation has been lowering just due to oxidation of organic material. The way to think about it, oxygen came in combined with organic material and essentially exhaled. The carbon went from solid state to gas. This was a major source of CO2 emission. I've often joked that, if this was a smokestack, we'd regulate it."
The Deltan quilt of drained fields sitting below the height of water in surrounding channels sets up gradient pressure, explains Mount. "So that water is trying to flow in the middle of the island. The levee is holding it back. Water seeps underneath the levee and comes up. There is seepage through the levees. All levees leak. Farmers have drains to capture that water and to pump it out. So some of the water flows through and farmers try to capture that. And occasionally, you have levee failures. This allows water to rush into these fields to fill this void. It rushes in fast. It's dramatic because of the power of water, usually a function of slope. If there's a big slope, these things scour holes that are more than sixty feet deep."
To Mount, there are two types of levee. "Ones that have failed and ones that will fail." However, farmers in the Delta argue that their levees are a third type, i.e.: safe. "They say the levees are 150 years old and really delicate," says Lynn Miller, whose family has farmed on the heavily sub-divided 32,879-thousand-acre Roberts Island in the South Delta since 1871. "That's not true. Seventy to eighty percent of them have had upgrades in the last thirty years."
By "they" Miller means anyone from outside the Delta who backs the governor's proposal to build a fresh water bypass system around the Delta and its levees. For Delta farmers such as Miller, any attempt to segregate and protect export water amounts to a grab that, if the much mocked "co-equal" goals of the 2009 Delta Reform Act are not enforced, could leave their remaining Delta water too salty for irrigation and kill public incentive to invest in their levees.
Out front of the Roberts-Union Farm Center, Miller stands with fellow south Delta farmer Joyce Speckman. Speckman's family ties to the Delta's poldered fields date back to the 1920s. Both women insist that no Delta levees have failed. By contrast, the state's Department of Water Resources puts the number at more than 100. Asked about the 2004 Jones Tract disaster in which a third of all the fresh water in the Delta was sucked into fields spanning 12,000 acres, Speckman responds, "That was caused by a rodent."
"There's reasonable debate whether it was a beaver or scour," says Mount. "The evidence was lost. It washed away. The forensics of levee failure is always complicated. Burrowing rodents are another risk."
Mount is sympathetic to Deltans such as Speckman and Miller. "Delta farmers say, 'We take good care of our levees.' I understand their point. They have made heroic efforts. The simple fact is there have been 144 levee failures. There have not been many lately. We have not had high inflows, high winds and high tides. But it's almost akin to saying it's been a long time since an earthquake." According to Mount, risks in the Delta are high because "there are multiple potential causes." Then he reels them off: overtopping, seepage, under-seepage, quakes. Ah, and rodents.
As if reflexively, Deltans reject the idea that a quake could trigger a cascade of levee failures -- a disaster scenario that the L.A.-based Metropolitan Water District of Southern California takes so seriously that its engineers have elaborate plans for a three-month effort to create an emergency "straw" to carry export water to pumps and canals through the chaos. Metropolitan, which supplies water to 19 million people, refuses to ignore the risk.
Stress trials by a UCLA team have shown that the Delta's peat and various levee fills are indeed vulnerable to liquefaction if a Napa-sized quake occurs on the Midland fault running beneath the Delta.
Joining the chorus of Miller and Speckman about how Californians should be reinforcing Delta levees and not tunneling around them is Rogene Reynolds, whose family ties in the Delta date back to the 1880s. She sees the future of the Delta in what are called "fat levees" -- double wide embankments topped by asphalt roads. During a tour last winter, she drove ahead of my companion and me as we followed her out to an area where the South Delta's levee system widens to the point it supports a generous two-lane road. The wider levee top worked a visual magic. The grade to surrounding fields seemed less dramatic. The East Bay Municipal Water District pipeline serving Oakland seemed just fine. Herons lighted on blue water. Fields warmed as morning clouds parted. A speedboat powered by.
"This is the Fat Levee," she said proudly. "When I hear people say the levees are going to fail, I tell them to come out and look at the Fat Levee."
Reynolds, a bright spark of a lady, is compelling. Central Valley farms and city dwellers from Oakland to San Diego get water from this place she calls home, a place where her Portuguese forbearers trapped beavers and dredged canals. In return for the water, all Reynolds wants is an investment in fat levees to protect a way of life as old as the Gold Rush. It may happen. Every island that fails will subtract huge amounts of Sierra streamflow that might otherwise go into reservoir storage.
However, it might not. Repairing the Jones Tract after the 2004 breach cost the state $90 million. That was one tract. Protecting the Delta's roughly sixty islands over time will cost much, much more. Given the underlying soils and rising sea level, it still may not work.
Study the frailty of the soils in the Delta and what to do about it and the subject swiftly stops being about infrastructure risk and becomes about people. The worst damn mess that Robert Bea has ever seen isn't just messy because the Delta's prodigious gasworks, transmission lines, highways, shipping lanes, farms and roughly a third of the Southland's water supply are all so vulnerable to wholly predictable, even inevitable, events. It's because they are being held hostage as a bargaining chip. If Deltans accept the science about levee failure and seismic risk and then acquiesce to the tunnels (as they have consented to export projects in the past), they will have to trust that the 2009 Delta Reform Act is worth the paper it's printed on and exporters won't take too much fresh tributary water and leave them with saltwater in their canals or standing on their roofs when the levees give way.
Trust of Southern Californians, however, is as rare as hens' teeth in these parts. Having identified me as a reporter from Los Angeles, Miller says accusingly, "What bothers me is they [scientists and policy-makers] worry about if the Delta is flooded then you won't have clean drinking water. If the Delta is flooded, we'll drown!"
To this kind of thing, scientists have no answer. Mount's group at UC Davis understands land and water. Civil engineers such as Robert Bea and the UCLA seismic risk team looking at subsidence in the Delta understand infrastructure. The Metropolitan Water District of Southern California understands water conveyance. But the biggest damn problem at the heart of the biggest damn mess is distrust.
Mount is weary of arguing the facts. "You don't need scientists," he says."You don't need politicians. You almost need psychologists. Basically it is a problem of human culture and behavior."
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