The California Department of Forestry and Fire Protection (Cal Fire) recently released new fire hazard severity zone maps for Northern California, and the 2.3 million acres of high wildfire risk have become a source of concern for many homeowners.
The maps date back to 1980 during the Panorama Fire in San Bernardino County, one of the first major California wildfires.
Cal Fire’s maps, currently a draft, outline “fire hazard severity zones,” which tell the likelihood — due to weather, terrain, and vegetation — of a wildfire starting and overwhelming a specific region. With phase two of the four-phase map update complete, the process is set to finish by March 24, when Southern California will be added.
“There are a plethora of factors that go into the building of our model. We look at the terrain, slope, aspect — whether you’re facing north, south, east, or west — fire history, and more,” said Frank Bigelow, the deputy director of Cal Fire’s Community Wildfire Preparedness and Mitigation.
The last time fire danger was assessed in cities was over a decade ago; however, the increase in wildfire incidents, including the recent Palisades Fire and the following Southern California wildfires, led Gov. Gavin Newsom to sign an executive order to prepare for future urban firestorms on Feb. 6.
“With the influx of the additional resources from legislation in the form of both money and people, we were able to accelerate getting these maps done and recognizing the events that took place in North Bay — the Carr Fire in 2017 and the Camp Fire in 2018 — and then subsequent fires in 2020, the need for these maps to be updated became a forefront for us,” Bigelow said.
The growing number of wildfires and their destruction underscores the importance of these revised maps and the fire safety measures that will be put in place.
“We are living in a new reality of extremes. Believe the science — and your own eyes: Mother Nature is changing the way we live, and we must continue adapting to those changes,” Newsom said in a press release. “California’s resilience means we will keep updating our standards in the most fire-prone areas.”
Executive Order N-18-25 requires the state fire marshal to update the maps of all California counties — categorizing them into three zones as either “moderate,” “high,” or “very high” — resulting in 1.4 million new acres classified as higher fire severity zones.
“We agree that it’s been too long, and we recognize that. We started this process of reproducing the maps in 2018 and really started to pull together the best available data and the smartest minds we could to help develop the next iteration of the model that we ran to determine the zones,” Bigelow said. “It went through a lengthy process of peer review throughout the science community to ensure that what we were creating was going to generate the outcome that would best represent the actual hazard on the ground.”
To accomplish this, several key changes and refinements were made to the 2007-2011 map system, particularly concerning the factors of weather and vegetation, according to Bigelow.
“In 2007, the team used a much broader brush when they painted the weather prediction model, so it didn’t account for a lot of microclimates throughout the state that are really important and define those areas. This time, we were more accurate,” Bigelow said. “We also updated our vegetation layer. We have a much better and clearer picture of the vegetation that’s on the ground — whether it’s in the northern part of the state redwood trees or chaparral along the coast — using much better technology.”
The new map data will likewise require building and other plans of these acres to be updated, as well as areas that apply to the Wildland-Urban Interface Code (WUI), regulations adopted by counties and cities to protect people and property from the spread of wildfires between vegetation and urban areas.
“Homes that are located in that area, which is determined by the fire hazard severity zone maps, have to meet a particular ignition-resistant type of construction,” said Christopher Valley, the building official for San Carlos. “Compared to other homes and in the flatter-lying areas, these homes are required to be more resistant to a fire event as we’ve seen in Southern California and other areas — Paradise and then Santa Rosa a few years back.”
The biggest changes can be seen in Sonoma County, where 9,412 of its acres are now listed as “very high-risk” from the previous 1,730 acres in 2007-2011. San Jose, Orinda, and Half Moon Bay also increased in the highest tiers.
Facing the opposite, Oakland has gone down from almost 11,000 fire-risk acres to only 1,945. Berkeley, El Cerrito, and Hillsborough have also seen a decrease.
The community is also undergoing changes as the order speeds up the implementation of “zone zero” regulations. These regulations require an ember-resistant zone to be built and maintained within the first five feet of a structure in a “very high-risk” area. Due to their facing a greater threat, the goal is to ensure that no combustible materials surround homes in these zones.
Many cities, especially those that have felt the effects of wildfires, have already made progress towards meeting the zone zero requirements, needing only minimal adjustment.
“Zone zero is something that we actually enacted with our new construction back in 2019, which we started referring to locally as an ignition-free zone, and we were requiring one for anything built in our Wildland-Urban Interface after 2019,” said Paul Lowenthal, the interim deputy chief and division chief fire marshal for the Santa Rosa Fire Department. “In 2022, we ramped it back up to not only require that ignition-free zone for vegetation, but fences within those first five feet to also be non-combustible.”
However, other cities that have yet to face a significant fire threat have a much longer road ahead in making the necessary adjustments.
“We have a lot of existing homes up in the hills that have been there for 50 to 70 years with a lot of mature trees growing around,” Valley said. “It can be very difficult to achieve a defensible space or this zone zero regulation, especially with existing development that is currently in the fire hazard areas.”
Besides needed changes to homes, insurance rates and bills are a large concern for many homeowners. While the State assures that increased rates due to these new fire zones shouldn’t be an issue, fire departments are still working to reassess and update their own maps to ensure that any additional burdens are justified.
“We’ve adopted a new ordinance here in Santa Rosa, a hazardous vegetation and fuels reduction ordinance that is applicable to our entire Wildland-Urban Interface, and there are parts of that ordinance that are as restrictive as some of the ‘very high’ and ‘high’ severity zone locations, so we will also probably reevaluate our existing wildland to see if there are any areas that we can actually take out of it, which would be a benefit to those community members within those areas that may have challenges with insurance and other issues,” Lowenthal said.
In addition to home fire prevention measures, the city also plays a critical part by ensuring residents understand emergency procedures when these measures are no longer sufficient.
“Our role, as the city, is to inform the public and educate them about preparedness for all emergencies, but also specifically wildfire emergencies,” said Quinne Woolley, a management analyst for San Carlos. “For example, two years ago, Redwood City had a wildfire that was super close to our border, so during that time, we were posting on social media and alerting via SMC Alert. We also occasionally will engage the community with preparedness web workshops.”
Bigelow emphasizes the importance of making changes and being well-prepared.
“Wildfire is not a new phenomenon. It’s been here longer than people have. The problem is we have more people now, and we have more people in harm’s way of those wildfires,” Bigelow said. “So the mitigations that we ask people to do, like retrofitting your home to be more wildfire-resilient or creating defensible space by clearing some of the vegetation on your property, are the two things that provide you the best opportunity to survive a wildfire.”
