If Sea Level Rose 21 Meters, What Would Happen to California? Disaster.

Long Beach Bay
Long Beach Bay | Screen capture from Firetree flood mapping tool.

Science writer Chris Mooney offers an incredibly frightening prognosis for sea level in an article Thursday on the website Grist, quoting a glacier expert as saying human industrial activity has already locked in 69 feet of sea level rise. If that's true, what would that mean for California?

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Mooney quotes Ohio State glaciologist Jason Box as making the apocalyptic pronouncement, which seriously outstrips commonly-quoted estimates of sea level rise by a factor of at least three. According to Box, despite recent articles downplaying the threat of melting of the Greenland Ice Sheet, a deadly combination of increased atmospheric carbon dioxide, atmospheric methane levels already at record levels and increasing, and global soot pollution darkening ice sheets has already locked in enough melt in Greenland and Antarctica to cause 69 feet of sea level rise. That's 21 meters, or about the height of a six-story building.

Box doesn't state when the rising seas will reach that point. He does tell Mooney, however, that we can postpone that eventual catastrophic melt by slowing down the activities causing the problem in the first place, especially burning fossil fuels.

We're not in a position to judge the veracity of Box's prognosis for our planet's ice caps, though he does have impressive research chops and credentials. But we did wonder what a 21-meter sea level rise would mean to California.

As it turns out, it would mean an environmental and economic catastrophe. We've made use of a handy tool created a few years ago by firetree.net, which you can explore easily. The map doesn't have a setting for 21 meters, so we've used the 20 meter setting to make our projections more conservative, if that is the right word.

The California coast is rugged and steep in many places, and along much of the state's coast a 21-meter sea level rise wouldn't change the map all that much. But the places where coastal and interior land would be inundated are some of the most-developed places in California, and damages would likely run beyond hundreds of triillions of dollars. Worst-hit would be the Sacramento Delta area: a giant inland sea would open up running from Gridley to near Merced. Sacramento and Stockton would be submerged under up to 40 feet of water, with both rail lines and major highways put permanently out of service. Needless to say, water intakes and conduits in this area that send fresh water to Southern California would be useless.

The cities surrounding San Francisco Bay would be almost as hard-hit, with the majority of the flatlands submerged. The South of Market and Mission Districts in San Francisco would sink beneath the rising Bay, and Potrero Hill would become an island. Water would reach as far as downtown San Jose.

It's worth noting that in the industrialized Bay Area, the majority of places inundated are where poor people are more likely to live. East Palo Alto would be gone, along with West Oakland and almost all of the city of Richmond.

Not that the affluent get off scot-free in NorCal: tony Sausalito and Larkspur and the southern half of the Napa Valley will drown.

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Imagine seawater cresting the 405 in Culver City. | Screen capture from Firetree flood mapping tool.

Coastal land in the state's southern half won't suffer damage as extensive in terms of sheer area submerged, but still, entire cities will vanish beneath the swollen Pacific. Santa Barbara will be hit hard, and Goleta essentially wiped out. Surf will lap up against the 101 north of the Lost City of Oxnard. The low spot in the coast where Marina Del Rey is now will become a bay stretching to the Baldwin Hills, and a larger bay will stretch from Gardena to Irvine. Signal Hill and Costa Mesa will be the largest of a few islands still poking above the waves, but Long Beach will otherwise be history, as will Westminster, and Carson, and enterprising survivors will be able to buy beachfront property in West Compton.

The rugged coast south of Newport Beach will limit the broad scope of damage to the South Coast, but downtown San Diego will be gone west of Interstate 5, and the mesas that run up and down the coast will become peninsulas as the canyons that separate them flood.

The largest area of damage in Southern California will be in the low desert, as the Salton Trough fills with water once the low divide between the trough and the Sea of Cortez is overtopped. All the cities in Imperial County will be gone, and seawater will extend northward to submerge Coachella, Indio and most of La Quinta. The berm between the Trough and the sea is about nine meters high and the low point of the trough -- at the Salton Sea -- is almost 70 meters below sea level, which means that whenever that berm gets overtopped, floodwaters will course down 260 feet of incline to get to the bottom of the hill. The result will be a flood nearly a hundred feet higher than Niagara Falls, with the entire weight of the ocean behind it. While flooding elsewhere in California will be horrific, the flooding of the Salton Trough will likely be unimaginably disastrous.

In other words, if we've locked in 21 meters of sea level rise, California faces a disaster that may well cost quadrillions of dollars, claim perhaps thousands of lives, and completely alter the way life goes on in California -- if it does. Not only will we lose thousands of square miles of land, much of it ecologically valuable and much more worth large sums, but we'll lose major transportation and infrastructure corridors, aqueducts, and what is turning out to be a center of renewable energy development in the Imperial Valley.

If Box is right about the scope of the damage we face, and he's also right about our being able to postpone it by changing how we live, he offers a bit of perspective on the costs of switching to non-fossil fuel power. For instance: compared with losing Long Beach, having ratepayers foot the bill for a feed-in tariff that pays 25 cents for a kilowatt hour of solar electricity seems like it might be a good deal.

For ongoing environmental coverage in March 2017 and afterward, please visit our show Earth Focus, or browse Redefine for historic material.
KCET's award-winning environment news project Redefine ran from July 2012 through February 2017.

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