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
