Rim Fire tests effectiveness of fuel treatment projects

by Cate Moore on October 8, 2013

The Forest Service has released a preliminary report assessing the effectiveness of several fuel treatment projects that were performed to reduce fire hazard in the Stanislaus National Forest and Yosemite National Park.  In the aftermath of the Rim Fire, which burned through 250,000 acres of the Stanislaus National Forest in August, 2013, data was collected to determine how well these mitigations worked.

Fire behavior exhibited within the fire was rated at high to extreme, with the fire making runs of 30,000 to 50,000 acres on two consecutive days.  Let’s see how well the mitigations proformed under these very demanding conditions

Rim Truck Fuel Break

This is a 15 mile long shaded fuel break with a total treated area of about 420 acres.  The treatment is designed to protect Pine Mountain Lake, Groveland and Big Oak Flat from wildfire coming from the Tuolumne River drainage to the north.  The major work was complete in 2012 and was in a maintenance regime.

Did it work? – Fire came from the north and firefighters built and held their line within the fuel break.  The fire did spot over the line a number of times, but the open fuel condition allowed firefighters to contain the spot fires and work safely and effectively to hold the fire from spreading and successfully defend these communities.

Peach Growers

This is a treatment area in and around a summer home tract and campground in the Stanislaus National Forest.  Activites included mechanical thinning, hand thinning, piling and burning of piles and broadcast burning in the area surrounding the development.  Within the development, small diameter trees and insect-attacked trees were removed to open the stand.

Did it work? – When the fire approached, firefighters put a dozer line around the community, then burned out the land around the houses, which would not have been safe without the previous fuel treatments.  Observations of fire behavior in the area noted that the fire changed from a very high intensity fire in untreated stands to a low to moderate intensity within the treated stands.

Bear Mountain

This project covered about 1813 acres within the Stanislaus National Forest.  The treatments used include mechanical thinning such as lop and scatter, thin from below and selective tree removal.  Prescribed fire was used as a followup in many sections.

Did it work? – There was little firefighting action in this sector.  Forensic evidence post-fire found great variability in treatment effectiveness due to slope of the land, treatment type, proximity of untreated vegetation among other unlisted factors.  In general, the treated units saw lower fire intensities.  In those stands where prescribed fire was used as a followup treatment, the fire intensity was significantly lowered and the survival of these stands appears very likely.

Hogdon Meadow Residential Area

This project is within Yosemite National Park.  The area includes offices, housing, maintenance yards, campgrounds and the sewage treatment plant for the park.  In the 1990’s, Yosemite started a prescribed fire and mechanical thinning program around this area. 1066 acres have been treated.

Did it work? – Embers landing in the protected area causing spot fires that were easily controlled.  An attempted backfire set by firefighters unfamiliar with the area foundered due to lack of fuel.  Fire intensity within the treatment area was mostly low intensity and firefighters felt the area was a safe retreat if the surrounding area became indefensible.


This is very encouraging evidence that fuel treatments can work to save forests and communities from wildfire.

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