Sea Level Rise: Time for a Barrage of New Ideas

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.

The ideal location for the Golden Gate Barrage, according to design projections from the San Francisco Bay Conservation and Development Commission

The ideal location for the Golden Gate Barrage, according to design projections from the San Francisco Bay Conservation and Development Commission

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 … Next Page »

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The Author

Wade Roush is a contributing editor at Xconomy.

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  • Chrrles

    Umm – these great minds are at work monetizing your personal information, not hydrological engineering. The “geniuses” working on this problem will inevitably come from these firms’ legal departments, lobbying the hell out of local, state and federal governments to pay for these massive projects.

    All of these plans require massive amounts of pumping to ensure that the Bay doesn’t turn into a salt-saturated Dead Sea. The amount of energy needed to realize these thought experiments will probably contribute more to Global Warming… and still fail.

    Nice try – but I wouldn’t be too eager to gamble the farm on a seemingly convenient technical solution like this; unless cheer-leading for the new economy is the real point of this article.

    • PayForItYourself


      Nobody forced Facebook to build its campus a sea level next to the ocean.

      • Ormond Otvos

        So they make it a sixteen foot dike. Big deal. And take the servers and backup generators out of the basement and onto the roof, under the solar panels.

  • Russ Button

    Nobody really knows how much the oceans will rise. I’ve seen projections of up to 20 feet, not 3 feet. Go up 20 feet and you lose much of Sacramento and the Central Valley, including Stockton. Of course given property values in Stockton, that might not be a bad idea…

    You’d also lose much of Oakland, Alameda and communities and businesses all around the Bay Area. If we can afford $100 billion on a high speed rail system to be used by hundreds of people, perhaps we can afford $100 billion to save the communities of millions of people.

    • hoboroadie

      Truly the very least of our worries is the city. The ecological displacement from inundating our estuaries and littoral areas is what is most concerning. The loss of so much arable land may also be of more concern to the human victims of this disaster.
      The list is getting longer everyday. Enjoy!

    • PayForItYourself

      Much of the Central Valley is already below sea level and it isn’t “lost”

      Move to higher ground and stop building at close to sea level when you border the sea instead of demanding other people spend $100B so you can continue to enjoy your sea front property.

      You’ve got 50-100 years to get moved, shouldn’t be a problem.

  • Edward Villarreal
  • a_random_guy

    If we stick to facts rather than fantasy, sea level has been rising less than an inch per decade for centuries. In the last 30 years or so, this has slowed down. See for official data. So we are looking at about 8 inches per century.

    This is nothing but a pathetic attempt to generate panic, so somebody can feed at the public trough.

    • zieroh

      Keep telling yourself that. The cognitive dissonance you experience when your home finally goes under water will be worth it.

    • Kisai

      This omits sudden loss of Greenland or Antarctic ice fields. Likewise ignores Post Glacial Rebound.

      A map I saw years ago basically predicts that the Pacific coast cities will have more time to feel the effects of global warming, while most of the east coast will have less time. The area between Florida and Texas in particular is already out of time. Whatever needed to be done is far too late (Hurricane Katrina.) We’re fortunate that on the North America Pacific coast that we don’t get seasonal storm surges. So that works in San Francisco’s favor.

  • Jack Brown

    Whatever. They talked about a variant of this way back in 1945, well before sea level rise was expected; the ‘Reber’ plan would have dammed the South Bay from San Mateo on down as a massive land reclamation project.

  • PayForItYourself

    No doubt the wealthy landowners in the Bay Area would insist on taxpayers in Toledo and Boise chipping in via federal funds to help preserve their wealth.

    I have a better idea, let nature run its course and if you want to build a dike to protect your property, go for it. The notion that there would be a “massive economic injustice” if some property owners built dikes and it “redirected” water to the property of people who didn’t is simply idiotic in the extreme. Building dikes around part of the San Francisco Bay won’t affect ocean levels even one tiny bit, the water that would have covered their property gets spread across the entirety of the ocean.

  • David Pease

    If we are truly “all one country”, why not desalinate the water and pipe it to the drought areas of the country – I’m sorry, water is not as profitable as oil – yet!

  • ncdave

    What a bizarre and delusional article. The fact is that there’s been no sea-level rise at all at San Francisco in 30 years. Look at the graph:

    There is no chance whatsoever of a 3 foot rise in globally averaged coastal sea levels by 2100. 5 inches is more like it. San Francisco will probably see about 7 inches.

    In the first place, despite massive greenhouse gas emissions of the last 2/3 century, the (very tiny) rate of sea-level rise hasn’t accelerated at all. In fact, the rate of sea-level rise hasn’t increased in more than 80 years.

    In the second place, about half of the IPCC’s projected rise in sea-level is in the form of thermal expansion in the upper layer of the deep ocean, which does not affect coastal sea-levels. (Ref: Archimedes.)

    Meltwater from grounded ice does, indeed, increase coastal sea-levels, but it has been doing so since at least the late 1800s. The last 3/4 century of anthropogenic GHG emissions have, thus far, caused no measurable increase in the rate of sea-level rise.

    Could the rate increase in this century? Perhaps a little bit, but since ~90 ppm CO2 added over the last 3/4 century has caused no detectable increase in the rate, it is not plausible that future increases totalling only about twice that over a similar time period could cause large increases in the rate.

    That is especially obvious if you know that increasing concentrations of CO2 have diminishing effects on temperature. MODTRAN calculates that 50% of the warming effect of current CO2 levels would be accomplished by just 20 ppm CO2 (for a tropical atmosphere w/ constant relative humidity). The NCAR radiation code says 40 ppm, but, either way, at the current 400 ppm we’re well past the point of diminishing returns w/r/t the warming effect of CO2.

    What’s more, it takes a lot of water to measurably raise global sea-level. The oceans cover about 3.618×10^8 sq-km, so a one centimeter global average increase in sea-level requires 10^-2 m x (3.618×10^14 m^2) = 3.618 x 10^12 cubic meters of water. A cubic meter of fresh water weighs 1000 kg, so (disregarding the salinity/density effects of mixing fresh meltwater with seawater) a one cm increase in sea-level requires about 3.618 x 10^15 kg = 3618 gigatonnes. Ice has a density of about 0.9167, so that’s about 3946 cubic km. In other words, 947 cubic miles of ice must melt and run into the ocean to raise the seas by one centimeter.

    That is a lot of ice.

    We don’t have sufficient long-term tide gauge coverage of all the world’s coasts to calculate a precise number for global average coastal sea-level rise. However, we can say with high confidence that it is between 1 and 2 mm/year, and probably closer to 1 mm than 2 mm.

    When I averaged the trends at the 159 long-term tide stations which NOAA had analyzed in 2010, the average sea-level trend was 0.6 mm/yr, the median was 1.1 mm/yr, and a geographically-weighted average was also 1.1 mm/yr:

    Since then, NOAA has expanded the set of long-term tide-stations which they’ve analyzed. There are now 238 (including 156 of the original 159). if we average the trends at the 238 long-term tide gauges that NOAA has analyzed, the average is 1.3 mm/year, and the median is 1.4 mm/year. The Peltier GIA-adjusted average and median are 1.9 and 1.6 mm/yr, respectively. (I haven’t calculated a geographically-weighted average.)

    If we exclude from that list all those locations for which Peltier (VM2) estimates 0.5 mm/yr or more GIA (either positive or negative), the result is a list of 143 sites which are are not greatly affected by GIA. The average and median of their sea-level trends are 1.6 and 1.5 mm/yr, respectively. If you add Peltier’s adjustments, the average and median are 1.8 and 1.6 mm/yr, respectively.

    If we further restrict that list of sites to just those locations for which Peltier estimates less than -0.25 mm/yr GIA, the average and median of the sea-level trends at the resulting list of 91 stations are 1.5 and 1.4 mm/yr, respectively. If you add Peltier’s adjustments, the average and median are 1.6 and 1.5 mm/yr, respectively:

    We can also repeat the above calculations using just tide stations which have data over a period of at least 60 years, to minimize errors due to known multi-decadal oscillations. For the full set of 159 such stations, the average rate of sea level rise is 0.7 mm/yr, and the median is 1.2 mm/yr:

    Restricting that list to just those 60+ yr stations for which Peltier (VM2) estimates less than 0.5 mm/yr GIA (either positive or negative), yields 69 stations. The average and median rates of sea-level rise are both 1.4 mm/yr, the Peltier-adjusted average is 1.5 mm/yr, and the Peltier-adjusted median is 1.45 mm/yr:

    Further restricting the list to just those locations for which Peltier estimates less than -0.25 mm/yr GIA, the average and median of the sea-level trends at the resulting list of 44 stations are both 1.3 mm/yr, and the Peltier-adjusted average and mean are both 1.4 mm/yr:

    The averages and GIA-adjusted averages of these varying sets of gauges range from 0.6 to 1.9 mm/yr, and the medians vary from 1.1 to 1.6 mm/year,

    1.4 mm/yr is probably about right. That’s equivalent to 554 cubic km (133 cubic miles) of ice per year, melted and drained into the oceans. At that glacially slow rate global sea-level will increase by only 4.75 inches by 2100.

    In addition, Peltier estimates that the ocean floors are sinking at a rate sufficient to account for 0.3 mm/yr sea-level fall. If that’s correct, it would offset an additional ~120 cubic km of melting ice per year. OTOH, some researchers estimate that up to twice that much water might be added to the oceans each by groundwater aquifer depletion.

    So, my best estimate is that 400-600 cubic km of ice melts and flows into the oceans’ each year. That enough meltwater to account for 1 to 1.5 mm/yr sea-level rise.

    What’s more, even though the rate of groundwater depletion has been increasing, the total rate of sea-level rise has not increased. That strongly suggests that the meltwater contribution to sea-level rise has probably been decreasing.

    In any event, to add an extra half-meter of sea-level rise by 2100 would require the melting of an extra 50 x 3946 = 197,300 cubic km of ice. Dividing 197,300 by 86.25 yrs = an extra 2288 cubic km of ice per year, or an average melt rate 3.8 to 5.7 times the current melt rate — a rate which hasn’t accelerated for more than 80 years. In fact, if the rate of increase were gradual, it would need to approach 10x the current rate by 2100.

    An increase of that magnitude, requiring the melting of an extra 47,335 cubic miles of ice, doesn’t pass the laugh test.

    What’s more, the only possible source for any very large increase in meltwater would be Greenland. But we know from historical records that Greenland was significantly warmer during the MWP, when there was a Norse agricultural community there, than it is now, and that it remained so for hundreds of years, without triggering a global increase in sea-level sufficient to have been noticed and recorded in any historical records.

    This article, and the sea-level projections that inspired it, are delusional nonsense.

    Dave Burton
    NC-20 Science Advisor
    Member, NC Sea Level Rise Impact Study Advisory Committee
    IPCC AR5 WG1 Expert Reviewer

  • Matthew Kowalsky

    No, just change your economic paradigm that continues to heat thr planet.
    Engineers think they can re-engineer Nature.

    Here we need a new application of Murphy’s Law: if you re-engineer it,
    there will be a bug for sure somewhere. In this case, the bug could
    just increase the impact of a natural disaster such as an earthquake or
    THe Golden gate is not Venice or Rotterdam.

  • Paul West

    Greenland is melting and rapidly! The latest empirical evidence shows sea level rise of 7 meters in 20 years or less? And If we get a huge methane burp (which is very possible) it will be sooner rather then later. Here, catch up on the latest from the arctic.

  • William Mckechnie

    Okay I have been saying this for years but nobody listens but one day someone might stop and think that I may be on to something. Experiment 1:- fill a swimming pool with half pebbles then the rest water to within 1″” off the top. Now for the next 1 year remove one pebble every 5 minutes till all the pebbles have been removed now where is the water level?

    Into the sea:-

    Under water volcanic eruptions spewing out out molten rock which then cools to form solid rock thus causing displacement, Ships, submarines, oil rigs, aeroplanes, helicopters, meteors have entered the sea thus causing displacement.

    Iso containers in their thousands yearly are dumped in the sea thus causing displacement, Cliff faces eroding into the sea.

    MY IDEA (Technology using solar powered vehicles thus not creating a huge carbon print)

    Every Country must take part in removing rocks from the sea. Those rocks can be put onto lorries and moved in land to fill craters, quarries, etc. In vast unpopulated area’s such as Nevada desert just as an example huge craters can be filled with these rocks. Sand taken from the sea can be used to fill in the gaps between the rocks.Now imagine 1 cubic mile laid with rocks and more and more added on top till eventually you have created man maid mountains. Cover these mountains with soil.

    Back to the bathtub this time fill the bath with water and drop in a dense sponge the water is drawn to the sponge watch what happens after 40 sponges have gone into the bath!

    Polar ice caps melting replace these with giant sponges that soak in water, each sponge can be fitted with a weight so it drops to the sea bed.

    Flooding:- Instead of using sandbags outside peoples homes use weighted sponges. Where there is a particular are where flooding is most dangerous buy land from farmer and dig down about 1 mile, and cover with safety grid to avoid anyone or animal falling down. next heavy downpour when water goes to this area the pits will fill and the land above will stay safe.

    Space travel:- Mercury has a magnetic field 100 times stronger than the Earth. Build a spaceship using electromagnetics and aim it for mercury as it is pulled it should pick up momentum and when nearing the planet the electromagnetics can be changed so same poles and then the ship can be sent on a new course using rocket power for further space travel.

    Silly idea’s I know ha ha ha but hey! who’s bloody sane in this world

  • Mathew

    Throw in the element of Peak Oil and Global Warming. The super power warmongers swung their axe at Iraq and Afghanistan to “take” the oil. Iraq they got. Afghanistan .. is the next base for some sort of slow and arduous push in for the Caspian Oil basin. This simple truth about declining Oil wrapped and disguised as Terrorism, Taliban and Isis.

    The christian dogma has a very popular set of words; “the end times”. Well yes we may be very very close to the end times for our 150 year old “greed-spike” called civilization.

    These two elements. Peak Oil and Global warming will step in for sure. Im pretty sure Mother earth is going to be the most vicious of them all. Well it will be vicious for us .. but for mother earth it is like a simple detoxification. We are the cancer. She know exactly what to do. Methane based extinction will a deeper form of detoxification for the greed and illusions of the 1% and the rest of the sheeple that is us.

  • Mathew

    Dave Burton the NC-20 Science Advisor. Hi. Your estimates and science may be quite calming but i think you will agree that we need to slow down our man made activities a bit. We are pretty wastefull dont you think.