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Public works: unusually high king tides and wind surge caused Larkspur flooding, not an atmospheric-river event
Summary
Public Works Director Julian Skinner told the council preliminary data showed tide elevations reached about 8.7 feet — roughly 1.5 feet above forecast — causing creek overtopping in Riviera Circle, Larkspur Plaza Drive and Redwood Highway; pumps, county help and contractors were used around the clock.
The city's public works director told the Larkspur City Council that the weekend flooding was driven primarily by unusually high king tides and wind- and pressure-driven surge, not by a large riverine storm.
Julian Skinner described preliminary tide measurements that showed a peak elevation near 8.7 feet on Saturday, about 1.5 feet above the forecasted high tide. Skinner said that by hydraulic mechanics, elevations above roughly 8 feet result in major street flooding in known low-lying areas: Larkspur Plaza Drive, Riviera Circle (the Larkspur Marina lagoon), and sections of the Redwood Highway corridor.
Skinner explained that in Riviera Circle tidal water flowed over creek banks onto streets and into a hydraulically connected lagoon; without pumps the lagoon is slow to drain back through small connecting pipes. The city ran multiple 6-inch pumps 24/7 with assistance from County Flood Control and a contractor on a nearby bulkhead project; crews faced clogging from debris and landscaping material and had staff on pumps constantly to clear intakes.
Skinner and the city manager said the event was notable because the forecast underestimated the tide elevation. The county's Office of Emergency Services helped coordinate response and consolidated documentation for potential reimbursement applications. City staff emphasized the analysis is preliminary and that a full technical briefing will be scheduled as an agendized item so the public can participate in next-step discussions and mitigation planning.
Council members asked what would have changed operationally if the city had been given the higher tide forecast; staff replied main differences would have been earlier public warning and more road closures; infrastructure actions are limited without more lead time.
