San Diego Fire Officials Keeping Close Watch On Record-Dry Vegetation
Friday, July 19, 2013
Aired 7/19/13 on KPBS News.
Dry brush is fueling an early start to dangerous wildfires throughout California. Vegetation moisture levels have reached record lows.
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Armed with a small orange tool kit, Stephen Fillmore walked up a chaparral-covered hillside in the San Diego East County community of Descanso.
"We've got scissors and a small saw and some loppers," he said as he pulled each tool out of his kit.
"When you look at these plants that are alive — the manzanita behind me or the chamise here in front of me — when we take these samples and take pieces off that, we’re taking live fuel moisture," Fillmore explained.
Live fuel moisture is the living part of the plant. Dead fuel moisture is simply dead branches or sticks on the ground, he said.
"You can see on the manzanita there," said Fillmore as he pointed to the dry shrub in front of him. "There’s some dead sticks coming off from it, some dead branches, rather, intermixed with the live. And so you have both live and dead fuel moisture in the same plant."
San Diego’s rainfall is four inches below normal. Some parts of the state experienced the driest winter on record. That’s left millions of acres of brittle shrubs primed to burn.
California firefighters have already battled more than 2,200 fires so far this year and the peak of the season is still months away.
Climatologists are warning some vegetation in San Diego County is the driest it has been for this time of year in nearly a century.
Fillmore clipped the newest growth from the tips of the chamise and filled his glass jars.
He said usually at this time of year, the plant is fully bloomed with little white flowers and holds enough moisture to stave off major fires for another two months. But this year, the native shrub is already critically dry.
"And because of that, they’ve been stressed, and when they’re stressed, they don’t put as many resources growing that new growth, flowering and putting out a seed crop," Fillmore said.
Fillmore took the samples back to the lab at the Descanso Forest Service Fire Station.
"So what we need to do is get the wet weight of this, which is the weight of the fuel when it’s still wet before we dry it," he said as he placed the jar on the scale.
Fillmore subtracted the weight of the jar, and measured the sampled in grams.
"So this is 200 grams, so we record the 200 grams as the wet weight and we just simply put that in the oven at 212 degrees F and cook it for about 24 hours," he said.
The oven cooked away the remaining moisture until the samples were bone dry. After they’re done cooking, Fillmore calculated the fuel moisture percentages.
"So this one was 200 grams when we put it in the oven and its now 194 grams, so its lost 6 grams of moisture," Fillmore said.
The samples all measured below 60 percent fuel moisture, which is in the critical threshold for fire danger. The fuel moisture dropped 8 percent from last month. The lowest Chamise fuel moisture dropped to is about 50 percent. At that level, the plant basically shuts down and stores all remaining moisture in its core until it rains again, Fillmore said.
Dry vegetation is a huge concern among the fire community because low fuel moisture creates greater fire intensity and higher and faster moving flames.
"The energy that the fire’s putting into sustaining itself gets lost when it’s trying to evaporate off that moisture," he said. "When it’s not having to do that, then the fire can put more energy into the flame lengths and how fast it moves.
Filmore trained firefighters on fuels and fire behaviors and said the environmental awareness can be life-saving on the front lines of a raging fire.
“The more that they know about the fuel moistures and all the other sort of environmental parameters that are happening on a fire, conceivably the safer they will be," he said.
The fuel moisture data is also passed on to fire and weather officials throughout the county and state who determine when to issue fire alerts and red flag warnings.
“So say tomorrow we’re at 100 degrees, the fuel moistures are at 60 and then you get a fire on a moderately steep slope," said Richard Bowen, fire engineer with the Cleveland National Forest.
He said under these circumstances, more resources would be on standby because it would be very difficult to suppress a fire to under 10 acres.
"If it goes over, say, 10 acres, that’s when it's reached its resistance to control where it’s going to take a lot more resources, a lot more planning, a lot more everything to get it under control,” Bowen said.
San Diego’s topography of steep canyons and foothills combined with a dry climate makes it one of most extreme fire behavior areas in the country, Bowen added.
Fillmore said they’re keeping a close watch on fuel moisture and maintaining a high level of response.
"I always say 'You never know what a fire season is going to be until the fire season is over,'" Fillmore said. "But what I do say is that this year, the stage is set. There’s a lot of potential out there."
“We’ve dealt with years like this before, and we’ll stick to our same safety tactics and try to protect the public," he said.