Preparedness & Recovery

Big Risk, Big Ideas: Flood Control no Longer Just Levees

A recently released draft plan contains some new and creative ideas that could help save hundreds of lives and prevent billions of dollars in damages.

by Alex Breitler, The Record, Stockton, Calif. / May 8, 2017
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(TNS) - Think outside the levee.

As concerns about the state's aging flood-control infrastructure grow, experts are seeking ways to address the San Joaquin River's big-time risks in less traditional ways.

We'll still need to strengthen our levees and dams in the future, of course. But a recently released draft plan contains some new and creative ideas that could help save hundreds of lives and prevent billions of dollars in damages.

There may be other benefits, too: Improving conditions for endangered fish, reducing pollution, or providing new recreational opportunities.

Most noticeably for Stockton, perhaps, the plan calls for turning long-dead Mormon Slough back into a functional waterway where it passes through the city, even adding nature trails and bike paths. This would take some pressure off the Calaveras River and, conceivably, reduce the scale of costly levee improvements.

"It would change the whole image of the channel. It has been kind of forgotten," said Jim Giottonini, director of the San Joaquin Area Flood Control Agency, which has pushed the project for decades.

The plan also promotes the long-discussed widening of a flood bypass at Paradise Cut near Lathrop, which could lower the San Joaquin River about 2 feet in Lathrop and Stockton. The bypass would shunt some water into the south Delta, avoiding the downstream urban levees.

One of the reasons that the San Joaquin is considered especially vulnerable to future floods is because it doesn't have bypasses such as those along the Sacramento River, to the north. Paradise Cut would not only provide such a bypass — albeit a small one — but it would also preserve habitat for sensitive species such as the Swainson's hawk while still allowing the land to be farmed when it's not underwater.

Farther south, the plan would allow for the river to intentionally flood low-lying fields in certain areas, which also could take at least some burden off downstream levees, though it's unclear how much.

An unintentional levee failure at the San Joaquin River National Wildlife Refuge near Modesto last February brought the river down about a foot at Vernalis, eight miles away. That provided a bit of relief, at least temporarily.

Flooding those areas in a planned, strategic way could make a real difference, said John Carlon, manager of the nonprofit habitat restoration group River Partners.

"This can buy time for people to evacuate," he said. "I think there's going to be a lot of public safety benefit."

Still more ideas: Taking climate-change induced floods on the Calaveras River and storing them below ground, which would address two problems at the same time; using better forecasting tools to predict when dams should release or hold back water; and improving public warning systems.

These alternatives won't be enough, experts say. Levee projects will remain critically important. The levees along the San Joaquin are inconsistent at best; the state plan calls for major upgrades along the western flank of Stockton to protect against a potential surge of water from the Delta.

But the need for comprehensive action couldn't be clearer. Climate change is supposed to hit the San Joaquin River basin much harder than the Sacramento River basin to the north.

The highest pinnacles of the Sierra Nevada tower over the San Joaquin. Today much of the precipitation over those mountains falls as snow that melts slowly; if some of it falls as rain instead, it will be harder for dams and levees to do their jobs.

Indeed, state officials say that the magnitude of floods in some San Joaquin watersheds may increase by 60 percent to 80 percent by late this century. The San Joaquin River could climb another 3 feet at Vernalis, which, on top of the high flows seen this year, would likely have been disastrous.

The extreme flood of the future could carry twice as much water as the 1997 floods that caused two dozen levee breaks in San Joaquin County alone. This future flood could kill nearly 900 people, according to one estimate, and cause $9 billion in damage.

The combined force of levee and non-levee projects could reduce the risk, though certainly not eliminate it.

Michael Mierzwa, a flood planner with the state Department of Water Resources, said flood managers nationally began looking at these so-called "nonstructural" improvements after disastrous flooding on the Mississippi River in 1993.

"We've been moving in that direction. But it's been at a snail's pace," he said.

In some ways, the plan is just a $2 billion wish list. There is no guarantee that money will materialize to make any of these projects actually happen.

It does, however, show which actions the state considers to be a priority.

For the Paradise Cut bypass, the Delta Stewardship Council has awarded $2 million in voter-approved bond money to the San Joaquin County Resource Conservation District, which, partnering with the conservation group American Rivers, is working with landowners to acquire easements to allow for periodic flooding.

Challenges remain. The floodwaters diverted through the bypass could threaten rural levees in the south Delta.

But the bypass has strong local support.

"We could get a 2 to 3 foot (river reduction) in Stockton," Mierzwa said. "Now we're talking about something big."

— Contact reporter Alex Breitler at (209) 546-8295 or abreitler@recordnet.com. Follow him at recordnet.com/breitlerblog and on Twitter @alexbreitler.

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©2017 The Record (Stockton, Calif.)

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