Marin tidal flooding drowns shorelines as more rain looms
Seasonal king tides and rainstorm runoff caused flooding along parts of the Marin County shoreline on Friday as the Bay Area headed into a weekend of rain and high winds.
The National Weather Service issued a coastal flood warning for the San Francisco Bay that will last through Saturday afternoon. Rachel Kennedy, a meteorologist for the agency, said the water would get deeper because of a weekend “storm surge” of 1.3 feet. A storm surge occurs when additional water is pushed inland by winds.
Kennedy said the king tide is forecast to peak around 10:30 a.m. Saturday, when the tide could reach 2.5 feet above the normal level, a height the agency hasn’t recorded since 1988. The tide level is anticipated to drop Sunday, but waters will still reach 1.9 feet above normal along the San Francisco Bay shoreline.
The flooding on Friday prompted the California Highway Patrol to close parts of Highway 101 at Lucky Drive in Corte Madera and Shoreline Highway in Mill Valley. A minor flood was reported at Coyote Creek in Tamalpais Valley, where the creek level reached 8 feet Friday morning, according to the county.
Corte Madera resident Emily Drake paddled her kayak across flooded streets and parking lots along Lucky Drive on Friday to assist stranded people. She picked up someone who was stuck at a flooded gym and needed to go to work, kayaking her to a bus stop.
“I’ve been just going back and forth, talking to people and seeing if anybody knows anyone who needs to get to a dry spot,” Drake said.
She expects the tide to be “pretty bad” on Saturday morning, when there will be a full moon.
“I expect I’ll be doing a lot of rowing,” Drake said. “I’m hoping that it’s blocked off so not as many people need help.”
King tides are caused by celestial events that include the position of the moon and sun. According to experts, the higher tides come when the Earth, the moon and the sun align in a straight line, bolstering the combined gravitational pulls of the moon and the sun.
These tides are receiving an extra boost because the full moon right now is a so-called “supermoon,” when the moon is closer to Earth during its orbit.
“This is going to be the maximum tide for the whole year,” meteorologist Jan Null said. “Everything is lining up at once. It’s not going to be end-of-the-world sorts of stuff. All of the lower-tier parking lots will probably be covered with water. Maybe some of the upper-tier ones, too.”
The coastal flooding followed a rainy transition to the new year. Mount Tamalpais had 3.38 inches of rain within a 48-hour period that ended Friday morning, Kennedy said. During the same period, San Rafael had 2 to 2.5 inches and Novato received 1 to 1.5 inches of rain.
Kennedy said Marin County could get 2 to 2.5 inches of rain this weekend. A wind advisory is also in effect. Dry weather is expected to return Tuesday, followed by possible light rain on Wednesday.
Roger Gass, another National Weather Service meteorologist, said isolated thunderstorms are possible in the region as well.
“The air mass is going to be colder in the system that’s coming behind the one that’s arriving Friday,” Gass said. “So generally, there’s probably 15% to 25% chance of thunderstorms, and I wouldn’t be surprised if there are some funnel clouds.”
The winds are expected to blow in a southerly direction, typical of an atmospheric river storm. Gass said they are likely to drop trees and create power outages but “they’re not going to be nearly as strong as what we experienced during the Christmas holiday.”
Bay Area News Group contributed to this report.