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A Marin County neighborhood with a deteriorating coastal barrier is already feeling the impacts of king tides and coastal flooding sweeping into the Bay Area this week.

The National Weather Service has extended a sweeping coastal advisory for Northern California until Sunday at 6 p.m. The North Bay started to feel the effects earlier this week when flooded roadways stranded a driver in Mill Valley, and now officials are focusing on a deteriorating 2-mile levee protecting 700 homes in an unincorporated community of San Rafael.

“This week’s high tides caused water to seep through or beneath portions of the timber-reinforced berm,” Marin County Supervisor Mary Sackett told SFGATE in an email. “With even higher King Tides anticipated around Thanksgiving and Christmas, we have a limited window to strengthen the most vulnerable areas.”

A full moon earlier this week created a gravitational pull and alignments of the Earth, moon and sun, according to the Associated Press. When that happens, king tides roll in and can last multiple days. 

The National Weather Service reports that the tides can inundate low-lying areas near shorelines and tidal waterways with up to 1.9 feet of flooding. This year’s El Niño has increased seawater volume and is exacerbated by Kelvin waves, causing an even higher sea-level rise, SFGATE previously reported.  

For the Santa Venetia neighborhood behind the levee, flooding like this can be disastrous. Bordering Gallinas Creek near where it empties into San Francisco Bay, the neighborhood was originally built as a luxury canal development modeled after Venice, Italy.

“So much of that area is an adjusted shoreline,” Quinn Gardner, the deputy director of emergency management, told KPIX-TV. “It’s built in landfill which is sinking, which at the same time, the ocean is rising. So, we’re in a double whammy situation there.”

On Oct. 5, the San Rafael City Council declared a state of emergency and warned residents about the expected impacts of El Niño. Sackett said the county is taking preventive steps, including asking creekside homeowners to allow emergency crews access to their properties for flood repair work. 

“The Marin County Flood Control District is preparing to install emergency flood protection measures, including steel sheet pile in areas with the most serious seepage, protective sheeting and sandbags, and water-filled barriers where conditions allow,” she said. “Crews will also monitor the berm during the highest tides, with materials ready to respond to developing problems.”

In January, a major storm caused $2.6 million worth of damage to the levee, SFGATE previously reported. In September, the Marin County Flood Control District submitted an additional environmental review for the proposed Santa Venetia floodwall — a massive upgrade to replace the current levee system. It has also asked property owners to consider donating an easement so it can use their property to “construct, inspect, maintain, repair or replace flood protection infrastructure.”