Now that the state’s revamped Central Valley Flood Protection Plan (big PDF) is out for public perusal, the question is whether the political will — and the cash — will be there to make it happen.

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California's status as an agricultural powerhouse is largely due to the fertile lands in the Central Valley, which are also prone to floods.

The Sacramento and San Joaquin river basins run through the valley and can overflow their banks threatening more than a million people and an estimated $69 billion in assets, according to the report. The current flood management system has been in place for about a hundred years and was designed specifically to keep water from the rivers off the land so that people could grow crops. Now the system has varied uses including conservation of habitat, water supply and water quality. The old system really isn’t up to the job anymore and almost everyone agrees that it will take a serious investment to bring it up to snuff.

“The system itself is beyond its design life,” says civil engineer Mike Mierzwa. “Think of it like an automobile. If you have a car it’s not going to run at top efficiency for 300,000 miles.” Mierzwa, who advises the state Department of Water Resources (DWR) explained to me that, “We’ve put a lot of ‘flood miles’ on the Central Valley’s flood management system and it’s really time for us to go through and find additional capital to actually improve its level of performance to today’s current design standards and needs.”

DWR outsiders are cautiously optimistic about the ambitious report. “This plan is really a framework. It’s not a plan,” says Jeffrey Mount, a geologist who directs the Center for Watershed Sciences at UC Davis. Mount says he considers the plan to be a step in the right direction. “If I could tweak anything it would be that this would be more integrated with other planning processes happening right now,” he told me. He’s concerned that the report punts on some serious questions about how climate change will impact the system and how conservation can be encouraged. The framework does mention those things, but leaves them to be studied more intensely down the road.

Mierzwa and Mount both seem excited by the idea of more bypasses — swathes of land next to rivers, set aside to carry excess water overland before returning it to the river. “They are very expensive because as you are going through and expanding you literally have to buy land,” said Mierzwa to explain why there haven’t been any new bypasses for 100 years. “But as you go through and you buy that land, you get a flood risk reduction benefit, you get an environmental benefit, and the benefits are shared throughout the entire system,” he concluded. The problem, however, is that the same land is highly coveted by real estate developers.

Mount is a huge proponent of bypasses. He’s not content to see the levees strengthened. He wants California’s long-term plan to recognize that restoring wetlands and other biologically diverse landscapes is not at odds with agricultural goals. ”People have this perception that you are going to let the water run wild across the farms and ruin everybody’s livelihood,” he sighed. “Nobody’s talking about that. We’re talking about some strategic areas to set the levees back, to expand bypasses, which will in some cases impact agriculture, but in many cases it won’t.”

Craig Miller/Climate Watch

The Yolo Bypass, which rarely floods to this extent, relieves flooding throughout the system and can become a wetland habitat.

Some farmers are already seeing benefits from allowing their land to be used for bypasses. Those who farm the Yolo Bypass, for example, got one-time lump-sum payments from the state, for use of the land (though some have suggested that a yearly payment would better serve farmers in planning for uncertain futures). Most of the time farmers can still grow crops — often rice — and they can do it on land that effectively costs them a lot less. They may lose their crops in a really big flood year, but the state’s payment is intended to make up for those infrequent occurrences.

The Central Valley Flood Protection Plan has to be approved by the flood board in July before it can take affect. During the next couple of years Mierzwa says DWR will focus on working with local groups to assess specific project needs, build capacity and talk about financing strategies. Mount says the cost of this plan is the “big, scary 800 pound gorilla” in the room. “It’s going to be hugely expensive. And we’ve come into a time when the federal government is no longer showing up with a fistful of cash for flood control projects.”

DWR put a price tag on its plan ranging between $14 – $17 billion dollars and insists that the state will only be responsible for part of that money. Mount says that’s an underestimate. “One of the big dangers is that local plans are often driven by development,” he explained. “It tends to be kind of ad hoc, rather than system-wide.”

This week officials made the uncomfortable decision to place thousands of homes and businesses in harm’s way, in order to avoid an even bigger catastrophe on the lower Mississippi River.

But as the opening of the Morganza Spillway was the subject of national media attention, California’s version had already been deployed a month earlier — and hardly anyone noticed.

The Yolo Bypass may be California’s most ingenious contrivance for flood protection and yet, many people drive over it every day without knowing its purpose.

The Yolo Bypass on March 1 of this year. The Sacramento skyline rises in the distance. (Photo: Craig Miller)

The bypass is a 59,000-acre funnel designed to catch the overflow of the Sacramento River and divert it harmlessly downstream, dumping it back into the main channel near Rio Vista. Generally speaking, it works like a charm. And it does so without fanfare because there are nobody lives there. That’s the idea.

Yolo Bypass on March 24, full of overflow from the Sacramento River. (Photo: Craig Miller)

“It is genius,” says Jeff Mount, who heads the Center for Watershed Science at UC Davis. “People come from all over the world to look at it because it the classic example of providing multiple benefits while managing floods.”

Upstream from Sacramento, the 31-mile Sutter Bypass serves a similar purpose. (Photo: Craig Miller)

Part of a system of weirs and bypasses that starts farther up the Sacramento Valley, the Yolo Bypass doubles as a wildlife refuge, providing wetlands habitat, and when it’s not flooded — which is most of the time — farmers grow rice there. Mount says the huge volumes of water creeping through the bypass also help recharge groundwater stores beneath the surface.

Part of the system is self-regulating. When the Sacramento River tops 33 feet at a point north of Davis, it flows over a fixed barrier known as the Fremont Weir, and into the bypass (captured in this video, posted in 2010). In more extreme situations, state water officials can open the Sacramento Weir, a series of manual gates that provides additional relief.

“It really is extraordinary,” Mount told me. “Sacramento would be wiped off the map by a vanilla (i.e. modest) flood, if it weren’t for the Yolo Bypass.” Mount has been a vocal critic of what he calls “serial engineering,” ongoing efforts to contain rivers to accommodate urban development. But setting aside buffers of land where rivers can flood naturally requires putting large swaths of valuable real estate off limits to development.

The idea is anything but new, first proposed by a 19th-century newspaper editor in the Sacramento Valley. But the idea took about 50 years to become reality. The Sacramento Weir was completed in 1916. To this day, when conditions warrant, crews from the state Department of Water Resources have to manually lift the cantankerous “timber-and-needle”gates, one at a time.

But the whole notion of the bypass has stood the test of time. “It is a miracle,” says Mount. “It’s the most happy accident you can come up with in this whole system (in which) somebody chose a dumb place to build the capital, at the confluence of these two rivers that get up and roar.”

But given the seemingly irresistible tendency to develop riverfront property, it’s a happy accident that’s not likely to be repeated.