By Wendy Langhans
Here’s a rule of thumb about “rules of thumb”: professionals take measurements and amateurs use a “rule of thumb”. For example, suppose you want to know what the weather will be like this evening.
If you’re a meteorlogist, you rely on measurements from the National Weather Service office in Oxnard. If you’re a mom, you remind your kids to “take a sweater”, just in case.
Firefighters are professionals and so, according to my “rule of thumb”, they rely on measurements. The LA County Fire Department’s Forestry Division measures “Live Fuel Moisture” twice a month. Samples are taken from specific sites in the Santa Monica mountains and in the mountains surrounding our Santa Clarita Valley, including, Bouquet Canyon, Castaic and Placerita Canyon. For a look at the July 2 report, go here.
According to the S-190 Wildland Fire Behavior workbook, fuel moisture is “the amount of water in a fuel, expressed as a percentage of the oven-dry weight of that fuel”. In other words, you gather samples of live plant material (in this case, Chamise, Purple Sage, Black Sage or California Sage). You weigh the samples, dry them in an oven, and weigh them again; the difference in weight before and after is due to the weight of water. Divide the weight of water by the weight of the dry sample and multiply it by 100. And voilà – you have the live fuel moisture!
These live fuel measurements are also plotted over time, comparing this year, last year and the ~30 year average. For an look at LA County measurements, go here. For a look at Castaic, go here. Right now, both local and regional levels are above the ~30 year average.
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But what do these measurements tell us? The LA County Fire Department website explains it here: “Fuel moisture determines if certain fuels will burn” and “how quickly and completely they will burn…” According to the professionals, “60% is generally recognized as approaching a critical level of live-fuel moisture.” And judging from the charts, we have not yet reached the 60% level.
But speaking strictly as an amateur, I’d suggest this rule of thumb – create a defensible space around your home. In other words, take a sweater with you.
Upcoming Outdoor Events:
Every Saturday at 11:00 AM & 1:00 PM. Family Nature Walk (11) and Animal Show (1) at Placerita Canyon.
For more information, click here.
Saturday, July 17, 8:00-10:00 AM. Bird Walk walk. Towsley Canyon. Get out in the park before the heat of the day and enjoy a bit of bird watching and exploration. Our bird guide extraordinaire, Volunteer Naturalist Roger, will share his expertise and considerable knowledge on this easy walk. Beginners are welcome. Bring your binoculars and meet at the entrance to the park. 2 hrs. For map, click here.
Trail Maintenance Schedule. Come join our volunteers as they help maintain our trails. Contact Steve at firstname.lastname@example.org for time and place.
Wednesday mornings, July 1, 14, 21 & 28.
Saturday mornings, July 10 & 24.
You can listen to stories like this every Friday morning at 7:10 a.m. on “The Hike Report”, brought to you by your hometown radio station KHTS (AM1220) and by the Mountains Recreation and Conservation Authority.
For the complete MRCA hike and activity schedule, directions to the parks and trail maps, go to www.LAMountains.com.