Scientists are mapping the areas most at risk for disastrous wildfires. These are the hotspots of the Bay Area

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The first radio dispatch reporting a wildfire one day in late May set fires to the hills on the eastern edge of Napa Valley, an area that had burned just five years ago in a huge firestorm.

From his office, Division Chief Brian Ham of the Napa County Fire Department clicked on the video feed from a fire camera perched atop a hill overlooking the Napa Valley. A thin column of gray smoke rose from the bottom of a drain.

Fire tends to climb, especially when buffeted by winds. Ham jumped into his truck. His colleagues who were the first on the scene were already calling for reinforcements.

There’s no way to predict exactly when or where the next wildfire will ignite, but firefighters and Bay Area residents know which hotspots are particularly vulnerable to any spark. In these places, the roads are narrow, the vegetation is dense and the dwellings mingle with the forests. Ham said it’s every community nestled in the hills along the Napa Valley.

“For me there is no area to fear – I am on high alert for every fire in every location,” Ham said.

Continued drought, minimal snowfall, parched vegetation and hot, dry weather are all conditions that put California on track for another “very, very difficult year of wildfires,” said Mark Ghilarducci, Director of the California Governor’s Office of Emergency Services.

Cal Fire scientists are revising statewide maps to help cities identify areas most at risk for catastrophic fires. They include the obvious clues: neighborhoods adjoining forests and grasslands. They add things like topography, fire history, and brush and tree types to better target the most dangerous areas. Cal Fire is meeting with local governments to refine the maps, which should be finalized and released in the fall.

Dark red patches cover parts of eastern Santa Rosa, from Pacheco Valle to Novato, western Martinez, towns on the northeast flank of the Santa Cruz Mountains. All of the Oakland Hills.

Daniel Berlant, deputy director of Cal Fire, said the agency is improving these maps to reflect “significant changes in our climate” over the past decade.

Weather is the final ingredient of fire risk. And officials are constantly adjusting their models to account for factors like wind, which has a huge effect on fire behavior.

“To be honest with you, every hour we take into consideration different weather factors and the likelihood of burning,” Berlant said.

Even the misty coast is ready to burn.

San Mateo County had seen little fog the week before a dry thunderstorm in August 2020 that sparked fires in northern California, according to Jonathan Cox, deputy chief of Cal Fire in the county. Major fires have erupted from the Mendocino National Forest to the Santa Cruz Mountains.

Neighborhoods along the northeast flanks of the Santa Cruz Mountains are marked on fire hazard maps in dark red, as is El Granada on the coast, home to the big Mavericks surf contest.

“When the fog isn’t there, we’re very susceptible to fire,” Cox said.

In Sonoma County, the usually coastal fog-tempered western county hasn’t seen many fires in generations. The area has dense forests and houses on narrow one-way roads. It’s the area Sonoma County Fire Chief Mark Heine is concerned about, though he stresses the risk “is everywhere.”

Heine said they were looking at what are called energy release models, which use moisture readings in plants and other factors to predict the ferocity of a fire. The models “are at all-time highs right now.”

The ancient 570-acre fire in Napa County, which started May 31 and was brought under control June 5, is the third-largest blaze so far this season in Northern California. PG&E has reported a problem with one of its lines in the area, although it’s unclear whether this was started by the fire or created the spark that caused it. The cause of the fire remains under investigation.

“Sonoma County to the Oregon border was at extreme risk of high intensity fires in June,” Heine said.

Narrow roads make it difficult for people and firefighters to move, adding risk to neighborhoods up and down the hills of Oakland. Homes are close together in these neighborhoods, and the woodsy atmosphere that makes these places popular also puts them at risk, said Heather Mozdean, assistant chief of operations for the Oakland Fire Department.

“Park like your life depends on it – pointed so you can get away,” Mozdean said.

On the northeast flanks of the Oakland hills, Contra Costa County officials have built shaded firebreaks — where ground vegetation is cleared and lower limbs removed from trees — to help keep the fire from spreading. encroaching from the west.

The fire season has never really ended in the county where more than 420 acres have burned so far this year, mostly on prairies and ranches, the spokesperson for the County Fire Protection District said. Contra Costa, Steve Hill.

More than 500 homes were evacuated before dawn Friday when a wildfire broke out in an open space behind a Pittsburgh neighborhood. Fueled by the wind, the fire burned to the backyards of dozens of homes. Hill said firefighters were able to fend off the flames because the neighborhood took care to clear brush between homes and the open space. The fire charred 122 acres.

“It’s no different in Contra Costa County than up north,” where the Old Fire burned, Hill said. “The urban-wild interface – we have it all. We have very high fire threat areas. We were lucky but we know the risks.

In Solano County, Vacaville Fire Chief Kris Concepcion recalled seeing 40-foot flames approaching the Alamo area on the northeast outskirts of town during the flashfires of 2020. The success in stopping the fire from burning over a 200 foot section of fence was luck – not wind – mixed with good planning. The fire burned from Pleasants Valley into a basin that had been aggressively cleared.

In May, the Quail fire forced dozens of people to evacuate to a rural area west of Vacaville. The fire was stopped at 135 acres.

No structure was lost and it burned through parched ranches and wild lands.

“That’s where we’re worried,” Concepcion said.

San Francisco Chronicle writer Emma Talley contributed to this report.

Julie Johnson (her) is a staff writer for the San Francisco Chronicle. Email: [email protected]: @juliejohnson

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