My friend Russel Kohn wrote a fantastic essay about his experience in the Topanga fire area. It includes lots of excellent background information about wildfire. With his permission, I am republishing his essay which he posted to a newsgroup we are both on.
On 9/30/05 10:12 AM, "Russell Kohn" wrote:
Fire is a normal part of the ecosystem here.
The Chaparral plant biome consists of a wide range of drought-tolerant shrubs and bushes and grasses. The plants contain oily chemicals that make them endure the heat, resist insects, and avoid being salads to birds and mammals. When the plants die, they do not decompose very quickly due to these same chemicals. Therefore, a fire is required every 7-15 years to burn out the old dead-wood and allow a new generation to thrive.
The fire season is in late Sept through the first real rains, usually in November. It is worst when the winds are blowing. Our usual prevailing wind is a gentle breeze generally from the Pacific ocean going inland. When a high pressure moves to our East over the Great Basin desert of Nevada, and there is a Low in the gulf of Alaska or off the West coast, then the pressure differential causes a large wind event that starts from the North, progresses to the East, and then bounces all over the place until the normal flow prevails. These "Santa Ana" winds can cause any fires that start to spread a dozen miles or more in a 24 hour period. The wind can be blowing from different directions in different parts of a large fire due to different micro-climates that arise, as well as to the focusing effects of valleys.
The best way I've found to think about these fires is that they are indeed "brush fires" or "grass fires". They will consume all the fuel they can, until it is gone. The "fire" is not in a single place; there are often multiple fronts at the leading edges. In a mature fire the fronts can be substantially disconnected so that it appears as though there are several separate fires, even though they started from the same place. Everything is smoldering.
The complex mountainous topography makes for interesting fire shapes as the fire lines crest ridges, go around knolls, and otherwise "flow" through the combustible material. If the wind is strong, you can general predict the rough direction of the fire because it will be "pushed" in that direction. In the most dangerous circumstances, large burning embers (or entire burning bushes!) will be blown up to 1/2 mile ahead of the main fire line and start spot fires ahead. This is called "spotting". When a large spotting fire is on the move, it can cover over 10 miles overnight. When the wind is not blowing, then the fire spreads only based on the available fuel.
All homes in fire areas here now have fire-resistant roofs, and must maintain adequate clearances around their homes ("defensible space"). In this way, when a front of the fire approaches the residences, the firefighters can simply make sure that the fire does not progress any closer to the homes than the defensible space. The fire will then "turn" and move laterally along the line, and work its way back against the wind using the fuel that is left and try to seek another path.
Firefighters generally don't try to "stop" the fire; they simply try to control the direction when it gets near homes and expect it will do whatever a force of nature tends to do. This works quite well.
Here's what happened on Wednesday:
Around 2:15pm I went to pick up my sons from school and as soon as I parked the car I could smell the distinctive smell of a brushfire. The weather was perfect for a fire - hot, dry, Santa Ana winds - but I could not yet see the smoke. About 15 minutes later I saw the smoke coming from the Chatsworth area, about 10 miles from my home. Since the smoke cloud was small at that point, and I could already smell it, that was a good indication that the wind was blowing in our general direction.
As the afternoon progressed, and the fire grew, I knew that there would be a fight to prevent it from moving into Box canyon, because once it got into there, there was really nothing to stop it in the Cheseboro state park. If you go to maps.google.com and enter 91301, then zoom out one level and grab move the map slightly so that Agoura Hills is closer to the bottom of the screen, and the 118 is near the top, you can see that the fire started at the upper right corner on the 118 near the train tracks.
I live near the 101 in Agoura hills. Once the fire moved into Box canyon in the mid afternoon, I felt it was probably only a matter of time before the fire works its way to the Oak Park area, which is about 3 miles north of me. I also felt it would inevitably work its way down Cheseboro and Palo Camado canyons to my East, and then approach Calabasas and Hidden Hills.
My main concern was if the fire would cross Kanan to my north and progress down the large ridge in the middle of Agoura because that gets rather close to my house.
As an aside, I've learned over the years that the media much prefers tight shots of flames and lots of blah-blah but rarely delivers solid or useful facts that residents can rely upon. Sensationalistic news rather than informative. "Wow, Bob, did you see that flame! Guess those bushes sure are flamable". And NEVER a wide shot that would allow any real locational references. Couple that with the fact that for nearly the whole night they kept referring to everything as "near Chatsforth" and bluring the names between the different small cities and residential communities near where I live and it was a complete mess trying to figure out where the fire really way.
So, around 10:30 at night I took a drive around my area to some high points to see what I could. I spoke with the firefighters at the station on Deer Hill, which I estimated would be first area in Oak Park impacted and we agreed things were on track for a "big show" but not a lot to worry about. There were no planned evacuations at that time for Oak Park, so I figured I had some time.
I then drove home and planned to sleep for a few hours, then take another drive, and then decide what to do as we had many hours before the fire would be close, and chances were remote that my house would be directly impacted. I was inclined to have my wife take my kids to her Mom's for the day just so they could get out of the worst of the smoke and stress, but thought I'd see what the morning would bring.
I woke up around 4:00am and got dressed and was just getting in my car to take another drive, when "WHOOOP WHOOOP WHOOP ... THIS IS THE COUNTY SHERIFF.....THIS AREA IS NOW ORDERED FOR IMMEDIATE MANDATORY EVACUATION ....WHOOP WHOOP". And sure enough, there were several squad cars going through the area, with personnel on foot pounding on doors.
I'm thinking to myself, what the F**? There is no way the fire got this close that fast. But I don't have time to check it out for myself and have to rely on the authorities. The officers going through our area were from far away: Bellflower, Garden Grove, Lynwood etc. as part of a large inter-agency "incident task force".
So, I happened to have my computer on (because I had been trying to find an updated fire map before leaving), so dashed off a quick message to some friends, proceeded to wake the family, get the photos, kids, dogs etc. in the car and got out of there. The whole time I was stressed because of the lack of useful information about where the fire really was and why were were being evacuated (not knowing). We had no trouble getting to my in-laws in Camarillo, about 20 miles away.
After my family was settled, I decided to come back to check things out. I had talked with a friend who stayed and all seemed quiet. While the main road into our area was closed, all the side routes were open and I had no trouble getting back. Very weird having so few people in our neighborhood, and absolutely no police presence. Total over-reaction on the part o the authorities.
I did a little more prep-work around the house (moved some flammable stuff as far away from the house as possible), cleared the yard to make it easier for Firefighters should they need to come in, set up a ladder to my roof and some long hoses. My thought was if the wind picked up and embers flew, I'd want to at least try to slow them down until the cavalry arrived.
The rest of the day I spent watching the fire from different vantage points, visiting with neighbors, etc. We were very lucky that the wind become much calmer. As predicted, by mid-morning the very mild wind was beginning to shift from the east to the west. The wind was very conflicted for most of the day but by around 4:30pm became distinctly moister and from the west. This was exactly what the weather and fire people had been saying all day. It meant that the fire would tend to move back on itself in some cases, and zig/zag further to the South (closer to the 101) near Calabasas...which is why some of those areas were voluntarily evacuated the day before. All very much as predicted. The news of course reported this all as being surprising and unexpected and extra worrisome.
Last night I retrieved my family from my in-laws, and this morning have been unpacking the car and trying to get organized.
Watching television the feeling is that everything is on fire everywhere. That is not generally the case. There can be areas of intense burning, and the smoke gets everywhere, but in general the fire is localized to specific fronts that move/change evolve in complex patters. The word "fractal" comes to mind.
There is no up to date fire map that people can refer to, so we are left to use our judgement about what is going on based on what we see and estimate. The television news is nearly worthless. When you are close to the fire, the smoke can be too thick to know what is really going on; it is hard to know what is happening behind ridges. I understand LA County Fire is updating their website to try to include updated fire maps and projections. That would be very helpful.
In the absence of solid information, the mind plays terrible tricks and builds up images of the worst possible scenarios. I found this great vantage point where I could see exactly what was happening nearby, and only then did I relax from the extra-induced stress of our early morning evacuation. The only people I saw near this spot were some neighborhood boys who rode their bikes and had the sense to move high to see what was going on.
The air is still very smoky here, and all over S. Cal for that matter. There was this satellite picture showing the smoke cloud going dozens of miles out over the ocean when the wind was blowing that way. Now all that smoke is blowing back over the city and other parts of S. Cal.
The exercise of having to grab what you can in 20 minutes and leave is interesting. I am not nearly as prepared as I should be in this regard.
Once again, thanks for your kind wishes.
Russell Kohn , Chaparral Software & Consulting Services Inc.
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