King tides, the highest astronomical tides of the year, are expected along the San Francisco Bay shoreline Friday through Sunday and may cause minor flooding, according to the National Weather Service.
At Richmond’s Inner Harbor, the tide surged to 7.2 feet Friday and is expected to peak again at 7.3 feet at 10:59 a.m. Saturday, according to predictions from the National Oceanic and Atmospheric Administration. The lowest tide is expected at 6:08 p.m. on Saturday.
A coastal flooding advisory has been issued by the NWS through 4 p.m. Monday.
King tides, which bring both the highest high tides and lowest low tides, usually happen about three or four times a year, said Dial Hoang, a NWS meteorologist.
“The impacts from the king tides are typically limited to the immediate coastal region,” Hoang said. “If you are going to the harbor in Berkeley you might see some of the trails and sidewalks getting flooded over, sometimes you might see parking lots near the bayside being flooded as well.”
With rising seas, these sea levels could eventually become the new normal.
Since 2010, the California King Tides Project has asked community members to upload their own photos of shorelines at these extreme tides and share them as data or participate in a king tides event in their area. If you’re up for a short road trip, there’s a free “wetlands edge discovery hike” in Napa County and group bike ride in Redwood City on Saturday.
Photos of king tides are important in helping agencies identify infrastructure — landmarks, staircases, sea walls, piers, roads and more — that are at risk from flooding as sea levels continue to rise due to human-caused climate change, according to the California Coastal Commission. All you need is a smartphone or digital camera.
To contribute to the project safely, tread carefully on slippery rocks and stay back from big waves. Keep your distance from seabirds taking shelter above the tide line, and never turn your back to the ocean. Photos can be uploaded to the King Tides Project map and shared on social media with #kingtides.
Why king tides happen
King tides are predictable. They arise from the gravitational dance among the sun, Earth and moon. The sun and moon both tug on the Earth’s oceans to create tides, but because the moon is closer, its gravitational pull is about twice as powerful.
When three astronomical events transpire simultaneously, we get a king tide. Usually, it happens in December or January.
First, there’s a new moon. During a new moon, the Earth, moon and sun are all aligned, with the moon sandwiched between the sun and the Earth. During this alignment, Earth’s oceans are pulled by the combined gravitational pull of both the sun and the moon on the same side.
Second, the moon is closest to the Earth in its monthly orbit.
Third, the Earth is at the closest point in its orbit to the sun, a time known as perihelion. This happens in winter, and it increases the sun’s influence on the tides.
Imagining sea level rise
As polar glaciers melt, the San Francisco Bay is predicted to see sea levels rise from one to three feet by 2050 compared to averages from the year 2000, according to a 2018 California Sea Level Rise Guidance report. Storm surges and extreme rainfall events could make it even higher. The Pacific Ocean will flood wetlands, roads and other low-lying coastal areas.
“The way sea level rise really will be felt is in these intermittent events of extra high tides and storms causing flooding, as opposed to a slow thing that creeps up on you,” said Plane.
While king tides are a natural phenomenon unrelated to climate change, they can make that future much easier to imagine, said Annie Frankel, statewide manager of the California King Tides project, part of the California Coastal Commission.
“Photographing today’s extreme high tides gives us a window into the everyday water level of the future,” Frankel said.
This story was first published on Berkeleyside where it was produced in partnership with Bay Nature, a nonprofit, independent media organization that connects the people of the San Francisco Bay Area to the natural world.
