San Mateo County has launched its new Tsunami Hazard Area Dashboard as part of a broader effort to better prepare for future tsunamis following last December’s chaotic response to a regional tsunami warning.
As part of California’s Tsunami Preparedness Week, the county’s Department of Emergency Management unveiled an online tool that allows residents to look at geographic areas designated as tsunami hazard zones before a tsunami happens.
“We cannot control emergencies, but we can control our preparedness,” said District 4 Supervisor Lisa Gauthier during Monday press conference unveiling the dashboard.
On the morning of Dec. 5, 2024, San Mateo County residents received a cellphone notification from the National Weather Service warning them of a potential tsunami triggered by a magnitude 7.0 earthquake off the coast of Humboldt County. One hour later, the warning was canceled.
The warning advised people in the tsunami hazard zone to retreat to higher ground. The tsunami hazard zone covered much of the county, including areas that were not actually at risk, according to District 3 Supervisor Ray Mueller.
“Everyone in the county received a National Weather Service tsunami alert, even though not everyone was in danger,” Gauthier said.
The broad scope of the warning spurred many people along the coast to drive toward routes like state Highway 92 that move eastward. The influx of cars resulted in traffic jams along the few roadways that connect inland.
“Many people ran to Highway 1, which is actually in the tsunami zone,” Mueller said. “They got stuck in traffic when they could have just gone few blocks east.”
After gathering feedback from the community, the county’s Department of Emergency Management identified areas of improvement to work on in preparation for future emergencies.
The Tsunami Hazard Area Dashboard is one development intended to ameliorate preparedness and efficiency before and during a tsunami.
The dashboard defines the exact areas in the county considered hazardous in the event of a tsunami. Specifying tsunami hazard zones minimizes the amount of people who need to evacuate, thus reducing traffic jams.
The dashboard is a map of the county shaded in either green or yellow. Yellow zones, which are hazardous during tsunami, include parts of coastal towns like Half Moon Bay, Pescadero, El Granada and Pacifica. Along the San Francisco Bay, minimal portions of Burlingame, Foster City, Redwood City and East Palo Alto are also in the yellow zone.
“On December 5, we heard so many stories about people who didn’t know if their children were in safe locations or if their spouses were in safe locations,” Mueller said. “They were traveling all over the coast in panic trying to figure out if they were safe and if who they loved were safe.”
The county also wanted to create its own resource since the California Department of Conservation’s online dashboard crashed on December 5 due to the magnitude of people trying to access the website.
“People on the San Mateo County coast went to a state website to see if they were in a zone that could be impacted,” Mueller said. “Because so many people were looking at that website, it actually failed … When this event happens again in the future, should it happen again, we know that county resources will be backing that website.”
Other updates intended to bolster the county’s preparedness for a tsunami include placing more warning signs in tsunami hazard zones. In several weeks, the county is planning to add high-low sirens to law enforcement vehicles that alert residents to evacuate during emergencies.
People can sign up for SMC Alert, the county’s mass notification system for communicating information during emergencies.
Additional tsunami preparedness resources can be found on the county’s website.
