MENDOCINO CO., 10/22/26 ā The ocean off the Mendocino coast is already running high, and printed tide tables probably won’t be “remotely accurate” this winter, a National Weather Service meteorologist said Wednesday.
Ryan Aylward, warning coordination meteorologist at the weather service office in Eureka, singled out the king tides that come right before Thanksgiving and Christmas, the winter’s highest tides, “because of the horrible timing.” A big storm during either could add storm surge and surf, he said in a phone interview. “It could be very impactful because we’ve already added an extra foot on top.”
His warning came a day after a UC Davis report mapped where El NiƱo flooding could cut California’s coastal roads this winter. Its examples start at Avila Beach in San Luis Obispo County and include Highway 37 in the North Bay. None is on the Mendocino coast.
Fraser Shilling, director of the UC Davis Road Ecology Center, calls his sites “examples of high-risk areas” that “are not the only areas of risk.”
At the low spot on Highway 1 just north of Point Arena, near the Garcia River, the trouble is the river and the tide together, not the surf, Aylward said. “When the river is really high and the tides are high, what we’ve found is the water backs up towards the highway,” he said.
“Mendocino Coast has a lot of bluffs, and most infrastructure isn’t right on the beach,” Aylward said. A 2019 Caltrans study found that 2 feet of sea level rise would reach 0.4 miles of state highway in Mendocino County.
At Arena Cove, “Highway 1 is way back there,” Aylward said. The cove itself has flooded badly, but only with big surf hitting the coast, he said. In a few low spots right on the beach, possibly including Caspar, large surf can run up and splash onto roads, he said. In other spots, splashing water and debris have reached Highway 1, though he couldn’t say exactly where.
On the Mendocino coast, Caltrans has closed Highway 1 at the Garcia River north of Point Arena and Route 128 from the Highway 1 junction to just west of Navarro during fall and winter flooding, Caltrans spokesperson Manny Machado said in an email in September. Maintenance crews watch both spots closely, he wrote.
“Highway 1 in that location floods almost every year and sometimes multiple times in a year,” said Laura Elisa Garza DĆaz, a water resources management adviser with UC Cooperative Extension in Ukiah, in an email in September. She meant Highway 1 near Manchester, around the Garcia River and Stornetta Flats.
Residents raised the issue when a countywide study of coastal roads and sea level rise, run by the Mendocino Council of Governments, gathered local input, she said. That study narrowed 23 coastal road sites to five priority roads in Caspar, Gualala, Point Arena and Fort Bragg. Highway 1, a state highway, falls outside it.
Garza DĆaz also pointed to Mamie Laiwa Drive near the Manchester-Point Arena Rancheria. “It’s the primary access in and out of the Rancheria, and there have been previous inundation concerns during heavy seasonal winter rains coinciding with king tide events,” she said.
On Oct. 6, county supervisors voted 5-0 to begin handing Mamie Laiwa Drive and Rancheria Road back to the Manchester Band of Pomo Indians. The band asked for the roads “so that they can maintain the roads by themselves,” county Transportation Director Howard Dashiell wrote in a Sept. 10 letter to the board.
How the UC Davis report works
Shilling used Climate Central’s public flood maps and checked them against flooding in Long Beach and Newport Beach this month. There, according to the UC Davis news release, an El NiƱo-driven rise in sea level called a Kelvin wave combined with a high tide and waves to raise the water 2 to 3 feet. Shilling then looked for other places that flood at that height.
“An historic El Nino could bring 100-year flood events,” he wrote.
The nearest of the report’s examples to Mendocino County are in Marin County and on Highway 37 in southern Sonoma County, near Sears Point and Tolay Creek.
The Kelvin wave itself is “topping 1 foot,” the report says. A coastal oceanographer interviewed in September put El NiƱo’s added push on the North Coast in the same range.
“There’s a surge of water coming up from the Equator that they think might add another foot to it, so that’s a lot,” said John Largier, a coastal oceanographer at the UC Davis Bodega Marine Laboratory.
Why the water is running high
The ocean at Arena Cove ran about a foot above the National Oceanic and Atmospheric Administration’s tide predictions Oct. 9 to 11, according to NOAA’s preliminary gauge data and the California Coastal Commission. As of Oct. 8, NOAA gave Arena Cove a 65% chance of topping its minor flood level on Dec. 24, the year’s highest predicted tide there.
Aylward said three things are pushing the water up. The ocean is warmer than normal, and warm water takes up more room. “Things that are heated expand. Air expands. Water expands,” he said. El NiƱo has also weakened the trade winds that usually push water west across the Pacific, so water is piling up on the eastern side. And the Kelvin wave is now passing California, he said.
“All three of those factors are likely leading to the higher water levels right now,” he said.
Tide tables could be off by a foot or more this winter, Aylward said. Point Arena was running less than a foot above predictions the last time he checked, he said.
He suggested checking the actual water level on NOAA’s Tides and Currents website, seeing how far it runs above the prediction and adding that difference to the coming tide. Everyone with any exposure to the coast “should definitely be on watch this winter,” he said.
The link between El NiƱo and winter weather “is weaker the farther north you go in California,” Daniel Swain, a University of California climate scientist, said in a September interview.
Flood supplies for Manchester and Point Arena
The county is working to set up caches of flood-fight supplies, probably including two on the coast, in Manchester and Point Arena, Travis Kilmer, the county’s chief recovery resiliency officer, told supervisors Oct. 6.
The weather service will post information on social media and its website ahead of high tides as forecasters gain confidence in how high the water will get, Aylward said.
The Coastal Commission’s King Tides Project asks the public to photograph the highest tides at Mendocino Bay on Nov. 24-26, Dec. 22-25 and Jan. 20-22. Calm weather would help, Aylward said. “Have a big storm that happens to hit right when those king tides are happening, and that could cause problems up and down the coast,” he said.
Away from the coast, Aylward’s advice is to get ready as for any winter. “We can have big river floods any year,” he said. “So we should be just expecting every winter the possibility of a big flood.”
Hwy 1 kisses beach sand in at least two locations in Mendocino County – Seaside Beach just north of Ten Mile River, and the bridge at Van Dam State Park. But there are also several stretches of highway north and south of Westport on cliff bluff faces that could slide if waves and tides undercut them at the base.
Hwy 1 where it crosses Elk Creek is very low-lying. I’ve never seen flooding there but high sea level, high tide and storm surge could change that. I’ve seen debris on the highway at Little River. I can remember the Gualala River bridge being closed due to high water levels in the river. In Sonoma County Hwy 1 often floods south of Valley Forge.