Shared from the 1/9/2020 San Francisco Chronicle eEdition

King tides a vision of future

Swelling seas this weekend offer opportunity for educational tours

Photos by Jessica Christian / The Chronicle 2019

Above: Caution tape is draped across Pier 14, closing it off to the public as large waves crash and cause flooding along the Embarcadero in 2019


Below: A man rides an electric scooter past floodwaters caused by the waves crashing into Pier 14.

Jessica Christian / The Chronicle 2019

A young boy who asked not to be named plays in the water as large waves crash into Pier 14 along the Embarcadero in 2019.

King tides, a naturally occurring phenomenon that received a common name only a decade ago, are heading to California shorelines this weekend — and with them, a series of public events intended to show people the dangers posed by sea level rise.

The aim isn’t simply to point out what really high tides look like, but to explain why they’re likely to swell higher and higher in the decades to come.

“Today’s king tides are the high tides of tomorrow,” said Lori Lambertson, a staff instructor at the Exploratorium, the interactive science museum at Pier 15. “They’re harbingers of what climbing water levels are going to do to the city and its infrastructure.”

Lambertson will lead hourlong walks on Friday and Saturday morning along San Francisco’s Embarcadero, an artificial line between land and water formed by construction of the city’s seawall in the late 19th century.

Tides along the Embarcadero will reach 6.7 feet above the average daily low tide on Friday at around 10:30 a.m., according to forecasts by the National Oceanic and Atmospheric Administration, and slightly higher on Saturday morning at 11 a.m. Last Friday and Saturday, by contrast, they were 18 inches lower.

Add the lapping of bay waters, or surges caused by passing ferries, and the extra height can be dramatic. During king tides exacerbated by warm water or falling rain, low points at Piers 3 and 14 routinely see water splash up onto public walkways, sometimes spilling into the Embarcadero roadway as well.

The most obvious Bay Area spot affected by extra-high tides is Highway 101 in southern Marin County, where the ramps at the junction of Highway 1 often fill with water. Because of the anticipated tides, Caltrans has closed a park-andride lot located there until Tuesday.

The Embarcadero walks are co-sponsored by the Port of San Francisco, which will also help lead a Saturday morning walking tour along Islais Creek in the Bayview district. The tour is being done with the city’s Planning Department, which is heading a newly launched effort to craft an adaptation strategy given the possibilities of future flooding as a result of climate change.

“We timed it with king tides so that it would be more dramatic,” granted Kirsten Southey, a spokeswoman for the port. “We want people to see what the future might be like in terms of sea levels.”

The pace and extent of future changes are unknown.

The most recent set of projections by the California Ocean Protection Council puts the “likely” increase in tides along the bay at around 40 inches by 2100. The council’s less scientifically rigorous upper-level forecast, done in 2018, suggested that daily tides could climb by nearly 7 feet.

Other Bay Area events scheduled this weekend include a Friday walk in Richmond beginning at the Shimada Friendship Park in the Marina Bay neighborhood. There’s a Saturday kayak tour of the Napa River, and Save the Bay is sponsoring a marsh restoration on San Leandro Bay.

The origins of the phrase “king tides” apparently dates to around 2009, when it was used by Australian scientists to describe a particularly extreme set of tides. The less catchy name — but more scientifically accepted — is perigean spring tides, a natural occurrence several times each year when the monthly high tide is amplified by the moon and sun being particularly close to Earth, coinciding with new or full moons.

This intensifies the gravitational pull that causes extrahigh tides. In California, they tend to occur in the weeks before or after the winter solstice.

“It’s the period of the year with the most predictable astronomical high tides, which are controlled by the pull of the moon and the sun,” said William Sweet, an oceanographer with NOAA.

According to Sweet, California isn’t as susceptible to widely shifting tides as is the East Coast, where sea levels already have risen to the point that cities such as Miami are seeing flooding on seemingly calm days.

But even if this weekend’s local king tides are relatively sedate, they’ll still put on a show.

“Sea level rise is not a gradual, uniform thing. It will wax and wane and ebb and flow,” Sweet said. “But the long-term patterns are accumulating. King tides give folks a snapshot of what’s going to occur.”

John King is a San Francisco Chronicle staff writer. Email: Twitter: @johnkingsfchron


Read The Chronicle’s series on the challenges posed by sea level rise in the Bay Area.


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