Bay Area Floods Foreshadow Extreme King Tides Around Thanksgiving
All week, high tides in San Francisco Bay have blocked Sasha Cole from reaching his home on the southern edge of Mill Valley — for several hours a day. Thanks in part to El Niño, that water filled the path to his houseboat just north of Sausalito.
Floodwaters also loaded the only drivable route to and from his home: the Manzanita exit on Highway 101.
“It’s been flooding every day, and when the off-ramp floods it’s impassable,” Cole said of Commodore Marina and the highway frontage road parallel to the homes. “When this happens, we’re stuck and can’t go anywhere for a few hours.”
Cole, who has lived on the houseboat for 11 years, said flooding is usually a several-times-a-year problem. But over the last several weeks, it’s almost become a daily issue, to the point where he has to choose between staying home to work and leaving to avoid the water.
“This would happen in winters past, and it was fairly predictable, but now it’s happening a lot more — and longer,” Cole said.
Tides were above seven feet by Thursday, and by Friday, around seven-and-a-half, according to Joe Merchant of the National Weather Service’s Bay Area office.
“This is the new norm for this winter,” Merchant said, as these water levels will hold throughout the season until the effects of El Niño begin to wane in the new year. “With the thermal expansion and the ongoing El Niño, it’s going to be an issue all winter long.”
High tide Friday around 1 p.m. was set for around 5.5 feet, but Merchant forecasted tides to reach 1.5 feet higher, because warm water is expanding the surface of the Pacific Ocean due to the effects of El Niño. Storm surge and waves could push water levels even higher.
Merchant expects high tides and coastal flood advisories next week as well, especially as the king tides, the highest of the year, begin to build around Nov. 20. The tides will peak the week of Thanksgiving.
Jan Null, a local forecaster who founded Golden Gate Weather Service, said this week’s tides, and any damage they bring, are “a preview of the king tides” in coming weeks and later this winter.
Null’s concern is with added conditions affecting king tides around seven feet: Temporary sea-level rise from ocean expansion as it warms due to El Niño, additional rise from Kelvin waves, larger surface waves, and any storm surge, could increase flood levels by a foot to several feet.
Any issues, flooding, or destruction during the king tide window provide an even wider glimpse into the future because of human-caused climate change — where daily high tides mirror this year’s king tides.
“We’re pushing the end rope right now, and we’re kind of seeing what climate change might look like 30 to 50 years from now, when the ocean has risen even more,” Null said.
It won’t just be communities along Richardson Bay that could flood during the king tide later this month, according to Daniel Swain, a climate scientist with UC Agriculture and Natural Resources. Coastal and inland areas could flood from Monterey Bay to Pacifica to along the San Joaquin-Sacramento River Delta.
These places could see “significant to record-breaking inundation due to elevated water,” Swain said, “especially if it’s combined with storm surge from low pressure, large waves at the immediate coast, or significant runoff from heavy rain.”
Cole, who has owned the houseboat since 2015, worries that if the tides rise too high, the ramp connecting to his community’s dock may break. He’s nervous the tides could snap the lines that tether his house to the bay floor, or worse, pull them taut and dip below the surface, letting water seep into his home. He wants to avoid the worst-case scenario: his house sinking.
“We’re all checking our lines to make sure that we’ll be safe if the tides rise to these kinds of unprecedented levels like nine feet and above,” Cole said. “I’m going to have to spend the next couple of weekends out here adjusting a couple of mine so that they don’t become weak points.”
In some ways, Cole said, he feels tethered to his floating home. He had planned to leave for Thanksgiving week, but with the possibility of the highest level of flooding he’s ever seen at his home, he thinks it might be best to stay.
“If a storm comes during Thanksgiving period, that will be just a whole other level,” Cole said.
“It will be beyond just kind of a minor inconvenience into the realm of not having utilities and water and not being able to get in or out for a few days.”
Plus, Cole said, if he stays home, he can help elderly neighbors with any issues that arise.
“If we’re cut off, and if we don’t have utilities, that will be maybe a little bit more adventure than all of us want in our lives,” Cole said. “I’m pretty able-bodied and capable of dealing with this. So to be here for my neighbors if something happens is important, if a boat breaks loose or starts flooding.”
Cole called this El Niño year a “harbinger of things to come.”
“We are living the conflict of climate change,” Cole said. “But it’s definitely happening ahead of the schedule I had in my mind.”