Southern Marin Flood and Storm Preparation Takes Shape

Officials have stepped up preparations for the coming months of king tides and potential El Niño-fueled storms in southern Marin.

Steven Torrence, director of the county Office of Emergency Management, was among a team of public safety officials who briefed the Mill Valley City Council on Monday.

The preparation efforts include better agency coordination; evacuation and “multiple-day scenario” drills; and an improved AlertMarin emergency notification system.

“We are collaborating among the agencies to ensure that we are prepared,” Torrence said, citing the county’s newly adopted 2026 emergency operations plan.

“Part of these briefings that we are doing with a number of cities and town councils and our district general leadership is going out and talking about how does the plan define the clear roles and leadership during emergencies,” Torrence said. “But also what we can do ahead of time.”

Tom Welch, interim chief of the Southern Marin Fire Protection District, said the area’s biggest concern is overlapping tidal flooding and hillside runoff or flooding from atmospheric river storms. The district oversees fire prevention in greater Mill Valley, Sausalito and parts of Tiburon.

“One of the risks that we deal with here in the valley is a combination of hazards,” he said. “Heavy rain all at one time, combined with high tides, and we have steep canyons. Those canyons bring the floodwaters down during the wintertime and they carry the fire up during the summertime.”

The next king tides are expected to crest on Thanksgiving Day, Christmas Eve and Christmas Day and in January. Shorelines and low-lying areas are most vulnerable.

The seasonal El Niño warming of the Pacific Ocean, which is now migrating north, has led to wetter winters in four of the last six reported cycles, Welch said.

Gov. Gavin Newsom recently proclaimed a preemptive state of emergency to bolster El Niño preparedness and facilitate financial assistance.

County and local public safety teams are planning a number of tests and public briefings in the coming days and weeks.

In recent weeks, public works crews in Mill Valley and across much of Marin have stepped up efforts to clear drainage systems.

At 10 a.m. Saturday, the county plans to test the AlertMarin system, which sends texts and emails with warnings in the days before anticipated events and instructions and updates during emergencies.

“We want to make sure that people have the opportunity to verify their information before we get into the upcoming winter season,” Torrence said.

AlertMarin has new features. Messages are now in English or Spanish. Users select locales and concerns such as coastal flooding and king tides; riverine and creek flooding; significant weather alerts; prescribed burns; and significant traffic disruptions. They can call a number to hear notices and instructions.

On Oct. 3, public safety officials plan to have an evacuation drill in greater Mill Valley. Later in October, Torrence said, the county will hold six public forums across Marin with local officials to encourage residents to do more to prepare and know where to turn for information. One focus is getting more 18- to 40-year-olds to sign up for AlertMarin.

Lindsay Haynes, the interim Mill Valley police chief, said 16,000 subscribers in Mill Valley have signed up for Nixle, an alert system that sends texts for severe weather, crimes, severe traffic, missing people or local events. Another popular app, Watch Duty, relays wildfire information.

“Nixle is mainly a platform that’s used for notifications, where AlertMarin is used for actionable items,” she said. “So please sign up for both.”

During their discussion, several members of the City Council said they did not receive notices during the king tides that closed Highway 101 last January.

“The first day of the king tide flooding there were no alerts that came out of our office,” Torrence said. “The reason that was the case is the collaboration between us and the state was actually not as clean as we needed it to be. The subsequent days … we had that coordination with the state.”

“Since then, we’ve actually improved a lot of the coordination between CHP, Caltrans and the county,” he said.

Torrence said all Marin residents will receive alerts if Highway 101 is affected.

“It doesn’t matter if you live in Mill Valley or Novato, you will get the alerts moving forward, as that is the commitment we are making,” he said.

The county also has agreements with utilities and telecommunications companies to send emergency alerts to every account holder, Torrence said.

The county also plans to post AlertMarin messages on other online platforms such as Nixle and Nextdoor to counter the circulation of inaccurate information, he said.

The county says fewer than half of the households in Marin have someone registered with AlertMarin.

“Our goal is to have one opt-in for every single household,” Torrence said.