Things have been feeling pretty desiccated here in the Golden State, but the return of the rains has been inevitable. And they could come as a deluge. At that point—when Corte Madera Creek swamps Marin, the Russian River jumps its banks and transforms Guerneville into a brimming slough, and much of the San Joaquin Valley turns into a duck marsh—well, we may miss these bluebird days.
That’s because our flood control systems are dilapidated. Some are on the knife-edge of collapse. Mostly built from the 1950s to the 1970s, they were viewed by engineers and citizens alike as state-of-the-art. Now they seem ill-conceived and poorly designed, based on notions hydrologists no longer consider valid. And calls for a new approach—one that relies less on human artifice and more on nature—are growing.
Flooding has always been a part of life in California, and much of our public infrastructure is dedicated to containing the worst of the damage. At first, we relied on earthen levees to keep flood waters at bay. But following World War II, abundant infusions of federal cash conjoined with the heated ambitions of young engineers fresh out of the armed services to take the state’s flood control efforts in an entirely different direction. Dirt was passé. Concrete was in. Lots of it.
“There was this massive boom in channelization,” says Bill Kier, a Cal graduate and watershed and fisheries consultant, “and it all happened in a relatively short time, mostly from the 1950s through the early 1970s.”
Across the state, hundreds of miles of natural streambeds went into concrete straitjackets. The idea, says Mathias Kondolf, a UC Berkeley professor of landscape architecture and environmental planning, was to create straight, precisely engineered structures that allowed water to move at “super critical flow”—a steady state where a maximum volume of water could be shunted downstream in a minimum amount of time.
“It was the ‘can do’ era,” Kondolf explains. “Anything seemed possible. We built the interstate highway system. We were going to the moon. So the idea that we could replace these annoying flooding streambeds with elegant channels? That was very appealing.”
Generally speaking, the channels worked well—so well that development often encroached on their verges. But they also had downsides. They require a significant amount of maintenance: Sediment must be removed from them on an ongoing basis, and damaged concrete sections must be repaired or replaced.
“They also don’t stop floods so much as move them,” says Kondolf. “Yes, a channel will transport high water quickly away from the area it’s designed to protect. But unless the river is channelized all the way to the sea, the water just shoots downstream, compounding the problem for people who live lower down the watershed.”
Moreover, concrete channels utterly destroy natural values, or “ecosystem services,” as the au courant phrase has it. A channelized river supports few if any fish, no trees or wildlife. In other words, it is no longer a true river.
That’s why concrete channelization is no longer in vogue. These days, the talk is of creating “sustainable” flood control systems—building set-back berms along rivers so flood waters can expend their energy in wide, natural corridors, or constructing bypasses, where floods can be diverted and dispersed across empty land.
Such approaches offer multiple benefits: Natural flood control systems can double as recreational or agricultural land, they improve water quality, and they are havens for fish and wildlife. The city of Napa largely solved its chronic flooding problems with a “natural” flood control project on the Napa River, and two large bypasses afford the city of Sacramento a significant degree of protection during high water events on the Sacramento, Feather, Yuba and American Rivers.
That’s all well and good, but vast tracts of developed land still rely on existing concrete channels for protection. Worse, many if not most of the channels are in a state of decay, suffering from the same lack of funds that is eroding our roads and hobbling our schools.
“Miles and miles of these channels are falling into disrepair,” Kier warns. “In some cases, you have trapezoidal sections of concrete that were designed to lie back from the rivers now falling toward them. And the fixes are going to be incredibly expensive. A bunch of us fisheries guys and hydrologists (including Kondolf) recently attended a conference on this issue. Mitch Avalon (Contra Costa County’s deputy public works director and deputy chief engineer for the county’s flood control and water conservation district) estimated that flood control structure repairs could top $2.5 billion in Contra Costa County alone.”
And who’s going to pay for this much-needed work? Maybe nobody.
“Basically, the Army Corps of Engineers built these projects and then handed them over to the local flood control districts,” Kondolf says. “Local agencies were left holding the bag, and they obviously don’t have the funds to deal with it on their own. The resources simply don’t exist. Marin County could spend its entire public works budget just on removing sediment from Corte Madera Creek.”
And what about Contra Costa County and its $2.5 billion repair bill?
“(Mitch Avalon) did the math, and based on current tax rates, the county might be able to raise $300 million over 30 years,” said Kier. “The message was pretty clear: These projects are unsustainable fiscally as well as environmentally.”
The idea that the state will merely wash its hands of flood control, of course, is absurd. Making the transition to more eco-friendly projects will be difficult —but a little creative accounting could help, allows Kondolf.
“If you only try to fund these projects with money earmarked for flood control, it looks impossible,” he says. “But we have to remember there are multiple benefits to these more resilient approaches. You have water quality and water table recharge benefits, open space for recreation and agriculture, fisheries and wildlife habitat restoration. Funds are available for all these initiatives, including state and federal funds. By drawing on all these different pots of money, you could achieve multiple goals—including flood control.”
Meanwhile, the state’s degrading concrete channels are engendering a false sense of security. The intensive development they have allowed, says Kondolf, constitute “a false promise, a sense that ‘Oh, the rivers aren’t really there (and pose no threat)’. In the long run, breaking up the concrete and moving to more natural and resilient flood control systems aren’t the greatest challenge. It’s dealing with encroaching urbanization. That’s much harder to address.”
So bottom line: Is channelization dead?
Kondolf labels them “relics from a different time, from a different mindset. Building new ones would be very hard to do today in California. Unfortunately, that message hasn’t gotten out everywhere. In the developing world, they’re building them like crazy.