A month after Lahaina was devastated by wildfire, Catherine Caufield, an Inverness Disaster Council area coordinator for upper Vision Road, joined Mark Brown, the executive officer of the Marin Wildfire Prevention Authority, to bring questions about evacuation and local fire behavior to our West Marin readers. Like so many other neighborhoods on the coast, Vision Road is forested and has few ways down to the highway. Their exchange touched on universal concerns arising from the catastrophe in Maui.
Catherine: In the event of a fire, the obvious way out from Vision Road is through Sir Francis Drake Boulevard, since the county evacuation plan says not to go uphill into forests. But if S.F.D. is crowded or blocked, would it make sense for residents to take the short fire road at the top of Vision (we have access to the combination locks), into the national seashore and then down to the beaches to wait things out?
Mark: Going downhill to Sir Francis Drake is absolutely the best way to go, even with traffic. The further up the slope you go, the more intense the fire behavior will be. Given your location, during an extreme fire weather day, fire would likely come from upslope rather than from below you. Moreover, any plan that relies on opening locked gates is a plan designed for failure. Often locks are locked out by other locks, or combinations change.
Catherine: That makes sense, but there’s truly only one way out of this community—and can we count on Sir Francis Drake not being blocked? The dangers were brought home to me as I saw people try to escape along a waterside road in Lahaina. I think Inverness would appreciate an explanation as to what to do if things don’t go the way we would like them to.
Mark: The idea of being on a blocked road during a wildfire is scary. But Inverness is a much different scenario than Maui. The terrain, fuel, housing arrangements and orientation to extreme wind patterns are all very different. Lahaina has a very gentle slope that allows the wind to contour down slope. It had light, highly combustible fuels that burned very quickly leading up to the community boundary. The homes are designed to have air flow through them for cooling effects, which increases ember distribution. There were no home hardening and fire smart landscaping efforts—the homes were essentially designed to burn, though not on purpose. The evacuation routes were lined either with these very combustible homes or decadent, dry and dying sugar cane.
Inverness, on the other hand, has very steep slopes that shelter lower areas from the types of winds that really drive wildfire. The fuels are very different, and while they can burn with great intensity, they do not burn at the speeds experienced in Lahaina. Most of Inverness does not have closely spaced homes, which is really what drove the home-to-home ignition in Lahaina. Inverness homeowners have also done more, though certainly not enough, home hardening and fire-smart landscaping, and we are hardening our escape routes.
We have modeled fire behavior under the worst weather conditions and conducted traffic modeling using high-powered computers. Our conclusion is that being on Sir Francis Drake Boulevard is safe, even during fire conditions. Fortunately, while the roads are narrow and windy, there are not enough residents, even taking tourists into account, to create significant traffic issues. We’re not saying there won’t be any, but they’ll be relatively minor and short-lived. Please believe your fire professionals when they say going to S.F.D. is your best option.
Catherine: Would a fire here always originate upslope in the forest? Or could it also originate closer to the bay and move uphill?
Mark: The best way to predict the future is to look at the past. The Mount Vision fire is an excellent example of the past—with those weather conditions. A truism about the coast is that it rarely has extreme fire growth potential, but when it does, get out of the way. On average, Inverness has around three to five of those extreme fire-growth potential days per year. It could be zero on some years, and more in other years.
On days of average fire potential, fires will have minimal opportunities to get large. The fire near Mount Vision in 2019 is a great example. Location-wise, that fire was in a terrible spot, and under the wrong conditions, we could have had a huge problem on our hands. But the extreme fire weather just wasn’t there, so the fire stayed small. For the first two days of the Woodward fire, fire potential was minimal. In fact, the fire only burned an acre or so in 36 hours. The problem was that we couldn’t get to it and the fire potential changed before we could extinguish it. Then it ran for 3,000 acres in half a day.
Fires in Inverness proper won’t begin in areas as inaccessible as the origin of the Woodward fire. Fires that start low on the slope along Sir Francis Drake will have a hard time coming up the slope under mild to moderate conditions; fires higher on the slope will have an even harder time burning downslope. About the only way a fire will progress downslope is through what we call “rollout.” That’s when something that is on fire roles down the slope and ignites a spot fire lower on the slope.
On extreme days, the wind will always come from north-northwest. This meteorological phenomenon is called the Foehn winds. The atmosphere lines up with the terrain to create winds and low humidity. The fire spread we saw in the 1995 Vision fire is what you should expect on extreme days. And, as you probably know, that fire did not get very low on the slope on the Tomales Bay side of the Inverness Ridge. The steepness of the slope and the ridgeline interrupt wind flow and a fire just can’t contour and penetrate downslope very well. And wind is the primary driver of fire in those conditions.
The further up the slope you go, the stronger the wind. That is why we are so emphatic when we say we want people to evacuate downhill, even if a fire is below them. Many firefighter fatalities have occurred when firefighters attempted to escape fire uphill. Similarly, if you evacuate upslope on Vision Road, you are likely going from an area with more safety and moving toward a more dangerous area.
Two more points came up in a recent online forum in which I discussed the differences and similarities between Marin and Maui with two fire experts. (The video can be viewed at https://youtu.be/51_fomP8Wq8?si=3qO1TeT9dpfoBgiW.) First, as we have been saying for a long time, the strength of our communities is the sum of its parts, and if everybody does their part, our communities will be resilient. All our residents need to work on home hardening and create defensible space through fire-smart landscaping. One home without home hardening and defensible space can threaten an entire community.
Second, please be aware of current wildfire conditions. Sign up for red flag warning notifications. The easiest way is to sign up for Nixle. Most weather apps on smart phones can be configured for red flag warning alerts. An understanding of current conditions and how wildfire burns will significantly improve your situational awareness and allow you to make informed decisions when wildfires occur.