King tides give San Francisco a watery glimpse of its future

City seeks solutions as coastal flooding could become the new normal

Rolling waves that breached city sidewalks and other low-lying areas over the weekend may offer a glimpse of what the future of rising seas will mean for San Francisco.

Called king tides, exceptionally high tides occur annually in coastal regions in December and January when the ocean is dragged back and forth by the gravitational pull of the moon and sun as their orbits align in specific ways with the Earth.

“This month, the moon is 7% closer than the average Earth-moon distance,” said Exploratorium educator Lori Lambertson. “So that’s going to bring up the tide higher.” In some areas, experts predicted tides of over 7 feet.

Last weekend’s king tides, an unscientific term for what’s known as a perigean spring tide, drew dozens of curious residents to the water’s edge on Saturday morning to hear Lambertson talk as waves lapped closer to the pavement’s edge.

But as climate change continues to fuel sea level rise by warming the oceans, melting ice sheets and expanding its volume, coastal flooding could become the new normal, putting The City’s infrastructure at risk of inundation.

“It’s really important for us to pay attention because this is really a look into our future,” said Lambertson.

Shortly before 10:30 a.m. Saturday, a rush of seawater sloshed onto the sidewalk sending the crowd running for higher ground. “It’s kind of exciting to see the water come up over the sidewalk where it shouldn’t be,” said Lambertson. “But when this starts to happen more and more frequently, it’s not just going to be a nuisance. It’s really dangerous.”

Much of The City’s infrastructure — including sewage treatment plants, the port, and other heavy industry — is close to the water’s edge, which could create a toxic mix as oceans begin to swamp coastal areas.

And, it puts some of The City’s most vulnerable residents at risk. “This is also an environmental justice issue because many communities who live near these areas are communities of color. And so, we need to make sure that we build a resilient climate future together,” said Lambertson.

Sea level rise is projected to increase 3 feet by the end of the century if we don’t slow the pace of global warming. This could imperil hundreds of thousands of Californians and nearly 400 of the state’s hazardous facilities including power plants, refineries and hazardous waste sites, UC Berkeley researchers found.

The City, which is expected to release its updated Climate Action Plan this week, already is addressing some of these issues, said Matt Wickens, an engineer for the Port of San Francisco.

“Sea level rise isn’t a new thing,” said Wickens. “The port has actually been implementing sea level rise projects that have been built in the last five to 10 years.”

Wickens referenced both the Water Emergency Transportation Authority’s expanded Ferry Terminal, which was built 5 feet above the shoreline to accommodate rising seas, as well as Fire Station 35 at Pier 22½.

“They actually built a floating fire station so that when sea level rises … they’re able to use that no matter what the weather, no matter what sea level rise happens in the future,” he said.

There’s also a massive project underway to upgrade San Francisco’s sea wall, which was originally constructed a century ago and is in desperate need of repair. Like much of the waterfront, the sea wall is built on weak bay mud, which puts it at increased risk during an earthquake.

The City committed $425 million to a project that would bolster the shoreline’s resiliency in 2018. The port is currently working to find the money to fully fund infrastructure improvements which it anticipates will cost up to $5 billion.

Wickens concedes there’s much work left to do. “It’s easy to solve the seismic problem, for example, but gaining elevation may be harder,” he said. “We want to think through those challenges and complications. And that’s kind of where we’re going with the adaptation strategies: How are we adapting, understanding the risks and leveraging the opportunities to solve the problems as they come at us?”

The immediate seismic and flood protection upgrades are targeted for completion by 2026. And every year, the tides continue to rise.

jwolfrom@sfexaminer.com

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