Everyone recognizes the Golden Gate Bridge. Even if you’ve never visited it in person, you’ve seen it in hundreds of movies and photographs.
But I’ll bet you’ve never heard of the Golden Gate Barrage.
That’s because it doesn’t exist yet. But as the atmosphere warms, ice sheets melt, and the unruly oceans slosh past their historical shores, the barrage may replace the bridge as the most famous engineering marvel spanning the tide-scoured entrance to San Francisco Bay.
“Barrage” is the technical term for a barrier across a waterway. The Golden Gate Barrage, a massive system of dams, locks, and pumps, would be one of the largest and costliest works in the history of civil engineering—but building it may turn out to be the simplest way to save hundreds of square miles of land around San Francisco Bay from certain inundation.
That includes property that’s currently home to Google, Facebook, Yahoo, Oracle, Dell, LinkedIn, Intuit, Cisco, Citrix, Lockheed Martin, NASA, and many of the other organizations that anchor the Silicon Valley technology economy. Much of the bayside land these companies occupy is already below sea level, protected by fragile earthen levees built decades ago. But these barriers are barely high enough to stop storm surges today, let alone the 18-inch rise in sea level expected by mid-century and the three-foot rise now projected by 2100.
All of which makes climate change an unavoidable problem for tech companies, not a distant conundrum for panels of researchers at the United Nations. And I’m not just talking about Silicon Valley companies. Six of the eight regions Xconomy calls home—Boston, New York, San Diego, San Francisco, Seattle, and Texas (especially the Houston area)—are at risk for huge economic losses as the oceans swell.
While it’s obviously crucial to slow the carbon emissions that are at the root of climate change, climate scientists say some level of anthropogenic warming and sea level rise is now irreversible, and likely to go on for thousands of years. Saving coastal cities and their residents will therefore require major engineering efforts—and coming up with new ways to fix things is supposedly the technology industry’s strong suit.
Already, New York Mayor Michael Bloomberg has proposed spending $20 billion to build a new system of levees, berms, flood walls, tide gates, breakwaters, and wetlands around the city’s coasts to blunt the effects of the next Sandy-like storm. Writers at Slate and Forbes have gone further, calling on New York to “think big” and investigate large-scale flood control systems like the Maeslantkering storm surge barrier in the Netherlands or the MOSE project to protect Venice and its surrounding lagoon.
In Boston, a commission appointed by Mayor Thomas Menino has recommended that owners of waterfront properties invest in flood walls, buffers, and backup power and water systems to prepare for future storms, the effects of which will be aggravated by sea level rise. The city government hasn’t yet announced a plan for dealing with the problem, but several of the mayoral candidates hoping to replace Menino have—state Representative Marty Walsh, for example, says it’s time to consider “a series of locks and dams ringing the city.” (Boston lucked out during Sandy, by the way—if the storm had hit at high tide rather than low tide, 6 percent of the city would have been underwater, according to the Boston Harbor Association, an environmental group.)
Outside Houston, the island city of Galveston, TX, home to almost 50,000 people, will see 10 percent of its land disappear underwater if sea levels rise by 3 feet, and more than half if sea levels rise by 4 feet, according to ClimateCentral, an organization of scientists and journalists. The city is studying a system of levees and and gates called the “Ike Dike,” a reference to the Hurricane Ike storm surge that devastated Galveston in 2008.
But the most dramatic proposal for saving a coastal region from rising sea levels—and the one that should interest Silicon Valley nabobs—is the Golden Gate Barrage.
For engineers and politicians working to mitigate sea level rise, San Francisco Bay presents both a huge challenge and a unique opportunity. Obviously, a huge portion of California’s wealth and economic prowess is concentrated here. In a 2009 study, the Pacific Institute, an environmental think tank in Oakland, estimated that a sea level rise of 1.4 meters would cause $100 billion in property damage along the California coast (in 2000 dollars), with the vast majority of this damage—$62 billion—occurring along the San Francisco Bay coastline. And that’s just the replacement value of privately owned buildings and their contents; it doesn’t include damage to public infrastructure such as the highways, railroads, hospitals, airports, power plants, and wastewater treatment plants that ring the Bay.
But unlike New York Harbor, Boston Harbor, Galveston Bay, Puget Sound, and other urban waterways, San Francisco Bay is a virtual bathtub. There is only one way for ocean water to go in and out, and that’s through the Golden Gate, a 300-foot-deep gap in the Coastal Range that was originally gouged out thousands of years ago by a mighty river.
As a result of this lucky geological accident, it would be possible in theory to control the water level in the Bay—to put a stopper in the bathtub drain—by building a massive tidal gate, more or less in the shadow of the Golden Gate Bridge. The ideal location, based on tidal velocities and the topography of the Bay bottom, would be about half a mile east of the bridge, as shown in the graphic above.
There has only been one serious study of the idea of a barrage at the Golden Gate, by the San Francisco Bay Conservation and Development Commission (BCDC) back in 2007. After weighing the potential benefits and costs, the commission came down pretty squarely against the idea. “Given the enormous cost, limited effectiveness, questionable feasibility, and probable significant adverse economic and ecological impacts of such a project, it does not seem prudent to seriously further consider such a proposal,” the report concluded.
But that was before the UN’s Intergovernmental Panel on Climate Change warned that a three-foot rise in sea levels is almost certain by 2100; before Sandy ravaged the East Coast and a “Pineapple Express” storm dumped an unprecedented 13 feet of snow in the Sierras in December 2010; and before a tsunami devastated the coast of Japan and sent a one-foot surge into San Francisco Bay. In light of our growing understanding of the climate picture, some observers are saying it’s time to take another look at the Golden Gate Barrage. (The project has also been nicknamed “Goldilocks,” since a major system of locks would be needed to accommodate ship traffic.)
In the design considered by BCDC, the barrage would be about two miles long and would rise 500 feet above the bed of the Bay. To maintain the character of the Bay-Delta system as a tidal estuary with a mix of salt and fresh water, and to deal with flood conditions during winter storms, the barrage would need to include pumps to bring a controlled amount of water into the Bay at high tide and send it back out into the ocean at low tide. In the early years, before ocean levels rise too high to permit a natural flow through the barrage, there might also be the opportunity to generate some tidal power using hydro turbines built into the dam. The design would also have to include a wildlife gate to give safe passage to fish, sea lions, and other critters.
The engineering challenges would be mind-boggling. But the attraction of the Golden Gate Barrage idea is that it would offer blanket protection to the entire Bay and Delta, saving numerous local governments and property owners from having to build levees. (The levee solution would almost certainly lead to massive economic injustice, as the Bay Area’s wealthiest communities and property owners rushed to build their levees first, redirecting the rising waters toward less-well-off communities.)
There are, of course, many potential flaws in the Barrage plan, and the political, environmental, and commercial objections would be numerous. For one thing, building the Barrage would create a single point of failure: if it broke, the whole Bay would be flooded. The BCDC also pointed out in its 2007 study that artificially restricting the flow of water through the Golden Gate would likely affect sedimentation patterns, salinity, animal migration, and the health of wetlands along the Bay. Then there’s the stupendous cost. The largest similar structure built to date, the Three Gorges Dam in China, cost $15 billion, and it isn’t nearly as tall as the Golden Gate Barrage would have to be.
But it’s an option we can’t afford to rule out, at least in the eyes of Ezra Rapport, executive director at the Association of Bay Area Governments. “Ultimately, this might be the solution, but I do not think it’s one we are quite ready to adopt today,” Rapport said during a March 2013 panel discussion at the Commonwealth Club in San Francisco. “We don’t have the engineering studies ready.”
If a single huge dam isn’t to your taste, there’s another intriguing idea on the table, called Folding Waters. Proposed by the San Francisco architecture firm Kuth Ranieri as part of a 2008 competition sponsored by BCDC, it calls for the installation of 15 permeable levees to protect the Bay’s most sensitive inlets. The levee tops would sit at water level, but would have wings that pivot upward with the rising tide, creating long waterfalls, similar to the edge of an infinity pool. The water would cascade into a shallow gutter, where it would be pumped back out into the Bay. More pumps built into the walls would create simulated tides to nourish the protected side of the levees.
No one knows how much Folding Waters, or the Golden Gate Barrage, would ultimately cost. Protecting the Bay with traditional levees, or new wetlands and tidal marshes, or a controlled flooding scheme, might turn out to be cheaper and more environmentally sound. The point is that it’s time to start doing the engineering studies. We need to figure out the likely costs, balance those against the costs of doing nothing (which are also stupendous), and then bring local, state, and federal authorities together to invent financing mechanisms.
One way or another, Silicon Valley corporations are going to get hit with part of the cost, so they might as well grab a seat at the table now. Maybe they can even divert a bit of their fabled brainpower to generating new engineering responses to sea level rise—preferably ideas that spread the costs evenly, promote equitable development, and preserve the Bay Area’s natural beauty.
The only other option is what’s called “managed retreat”—that is, admitting that the rising waters are unstoppable, ceasing all waterfront development, and gradually moving people and infrastructure to higher ground. But at the moment there isn’t anywhere for companies as big as Google, Oracle, or Facebook to go. And I just can’t see municipalities voluntarily abandoning big chunks of their territory—also known as their tax base—to the sea.
But with the right ideas, maybe a rising tide really can lift all boats.
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