The ocean takes center stage during the king tides, predicted to arrive on the California coast this Wednesday through Friday, and then again Dec. 4-6 and Jan. 1-3. Waters climb to their highest point of the year, flooding some Bay Area beaches, stairways and streets before plunging to their lowest, exposing stretches of sand and reef usually hidden. The spectacle draws photographers, beachgoers and scientists alike, because beyond the beauty, king tides reveal how the coast is changing.
Tides are familiar to anyone who spends time by the sea. Simply put, “Tides are bulges of water that the Earth rotates under,” says Serena B. Lee, a physical oceanographer at California Polytechnic State University. King tides are the extreme version, occurring only a few times a year when the sun, moon and earth align, intensifying gravitational pull and driving water higher than usual.
For researchers like Lee, these events are golden opportunities. Although tides are predictable, they remain under-monitored along much of the California coast, including Santa Cruz. Lee and her team are developing low-cost tidal gauges to track water levels in these gaps, especially during king tides, when extreme highs mirror the levels scientists expect to see more often with future sea-level rise. “The best time to plant an orchard was 30 years ago. The second best time is now, and that’s the same with collecting data,” Lee says. Tracking these changes provides real measurements, not just predictions, helping scientists, surfers and beachgoers better understand the rhythms of the sea. Lee hopes to eventually make the gauges available for public use.
At UC Santa Cruz’s Center for Coastal Climate Resilience, researchers are also seizing the moment. Computer scientist Alex Pang and graduate student Mona Zhao are using webcams, machine learning and 3D modeling to track how beaches shift from day to day. During king tides, the intertidal zone — the stretch between high and low tide — expands dramatically, letting researchers collect detailed data and map more of the shoreline. Pang calls the project “an important building block” for other potential research. Zhao adds that by removing the need for manual measurements, this method may help scientists more efficiently plan protection of our shores amid erosion and development.
Residents can join the effort through the California King Tides Project, which invites people to photograph high tides along the coast. “It’s a launch pad for communication with other people, with other members of your community, about what they’re seeing and experiencing, which is very powerful,” says project manager Annie Frankel. No special training is needed, just curiosity and a camera. The photos, archived on the project’s website since 2018, help visualize future sea-level rise and spark conversations about protecting the coast.
While king tides can be mesmerizing, they also demand caution. Lee, an Australian-born surfer, urges anyone venturing out to know their limits and stay alert. At their lowest, king tides expose critters usually shielded by water; at their highest they shrink habitat for other wildlife. Frankel encourages visitors to give animals space, watch their footing and never turn their back on the ocean.