Marin County officials are warning residents along southern Marin shorelines to prepare for flooding as a five-day king tide event begins Sunday, Aug. 9, and runs through Thursday, Aug. 13.
NOAA is forecasting exceptionally high tides during the period, with the worst expected during the evenings of Aug. 9 through Aug. 11 and shortly after midnight on Aug. 13, according to a county warning reported by Patch citing the federal agency's forecast.
County officials warned that recent king tides have run 0.4 to 0.8 feet higher than predicted because of warmer ocean water and windy conditions. That extra height increases the risk of flooding in low-lying areas of Corte Madera, Larkspur and Tiburon.
January's flooding offers a preview
Residents in those communities know what high water looks like. During the January 2026 king tides, Highway 101 flooded in both directions near Corte Madera, forcing traffic diversions at Sir Francis Drake Boulevard. In the Larkspur Marina neighborhood, streets turned into rivers and parking lots into lakes, CBS News Bay Area reported.
"Our message: turn around. Don't drown. If you need help, call 911," Central Marin Fire Battalion Chief Brian Peterson said on Jan. 3 during that flooding, as ABC7 reported.
More recently, a June 2026 high-tide event prompted road closures near Doherty Drive and Lucky Drive in Larkspur and on Lucky Drive, Fifer Avenue, Redwood Highway and portions of the Boardwalk and Golden Hind Passage neighborhood in Corte Madera, according to the Central Marin Police Authority.
Why this event could be worse
The current Super El Niño is compounding the risk. Warmer ocean water from El Niño temporarily raises sea levels six to 12 inches, Bay Nature reported in an Aug. 6 report. That comes on top of six to 12 inches of long-term sea level rise since the early 1900s, meaning king tides now start from a significantly higher baseline.
Climate scientist Daniel Swain of the California Institute for Water Resources told Bay Nature that coastal flooding will likely be a recurring problem regardless of other weather factors because of the current Super El Niño.
Under Senate Bill 272, Larkspur and Corte Madera must prepare sea-level rise adaptation plans by January 2034. Tiburon and Mill Valley have separate grants for their own plans, according to the Marin Independent Journal.
How to prepare
County officials are urging residents and business owners to take these steps before Sunday:
- Clear debris from gutters, storm drains and driveways
- Use sandbags where appropriate
- Avoid parking in low-lying areas
- Secure loose outdoor materials
Officials also reminded the public never to drive or walk through floodwaters and to obey all road closure signs and barricades. The county has not published a specific list of roads on watch for this event, but historically flood-prone roads could be affected.
Residents who experience flooding should call 911 for emergencies or monitor local public works channels for road closure updates beginning Sunday evening.
