Fourmile Canyon Fire Report Confirms Firewise

The Rocky Mountain Research Station released its Fourmile Canyon Fire report, requested by Senator Udall of Colorado. The Report confirms that:

1) A home’s fate depends upon fuel in its immediate surroundings and construction materials;

2) Fuel treatments, especially those that leave fine fuels untreated, are ineffective protection against wildfires that threaten homes, i.e., windy, dry conditions; and,

3) Fire suppression resources are easily overwhelmed precisely when Fire-Unwise homes need them the most.

The report took a special look at aerial attack, finding that the great preponderance of retardant was dropped after the fire had already stopped advancing.

6 thoughts on “Fourmile Canyon Fire Report Confirms Firewise”

  1. Here’s a piece by Bob Berwyn on the report..

    Also, my understanding is that the fuels treatments done were tiny and mostly directed at making access safe, so they did not really attempt larger scale fuels treatments in this area.

  2. Here’s my take: across the 6,000 acres, there were 600 acres of “fuel treatments.” In some of these, surface fuels had not been treated, and in fact thinning without dealing with surface fuels made the situation worse than untreated. It sounds like it’s important to finish a fuels treatment project for it to be successful. It also sounds like you need to keep up the treatment of fine fuels, in terms of prescribed burning, for it to be successful through time. Yet that size of a prescribed burning program, so close to homes, might run into a fair amount of trouble both from air quality and from concerned neighbors.

    The area of this fire is not too far from the area described in this piece from our blog on air quality and prescribed burning.

    My summary would be:
    1) document what you want to change in your fuel treatment (what kind of fuels) and why (defensible space for firefighters; strategic points; safe egress for homeowners).

    2) Look at if you could do enough acres/ kind of treatment to really make a difference, depending on your answer to 1).

    3) Finish the treatments including burning piles, as soon as you can.
    4) Remember that treatments require maintenance through time.

    For those who do not want to read the whole report, here is the part on fuel treatments:

    Fuel Treatment Efficacy
    Approximately 600 acres of fuel treatments had been performed within the area ultimately
    burned by the Fourmile Canyon Fire (Figures 21, 43). After any fire, little evidence remains of when and how treatment units were encountered and burned. This creates considerable uncertainty as to the explanations behind what can be observed post-fire. For example, treatment effects can be very different if the fire was heading (with the wind and or slope), flanking, backing down slope, or if it burned as a result of a mass ignition by spotting (Figures 30, 32, 33).
    Fuel treatment performance can only be evaluated post-fire based on evidence of changes in fire effects on residual vegetation and sometimes changes in fire progression. It was clear from photographic evidence that pervasive spotting (0.5 mi at 1000 and 1.0 mi by 1400 on September 6) during the Fourmile Canyon Fire allowed the fire to easily breach the narrow fuel treatments located throughout the area where the fire burned (Figure 21, 43).
    No evidence that fire progression was altered by treatments was found and the treated areas were probably of limited value to suppression efforts on September 6 because of the intense fire behavior (Figure 32). In some cases the fuel treatments were noted as being ineffective in changing fire behavior because of the large amount of surface fuels present, and because they were not maintained (Boulder Incident Command Team 2010) (Figures 23, 31).
    Firelines were built in fuel treatment areas on September 8 near Church Camp, but the fire never reached these areas and the final fire perimeter was not coincident with the location of the known treatment units (Figure 43). As such, the changes in fire activity in this area were primarily a result of changing weather (increases in humidity and decreases in wind, see figure 28) and topography (northerly aspect) rather than because of changes in forest structure and composition as a result of a fuel treatment.

    Several miles of roadside fuel treatments were designed to allow for better
    driving site distances along the steep and narrow roads but it was not possible to assess the possible role these treatments had in assisting evacuations (Figure 44).
    Post-fire satellite imagery clearly showed the absence of changes in stand condition inside treated areas compared to neighboring untreated stands (Figure 43). In some cases, treated stands burned more intensely than adjacent untreated stands, perhaps because of additional surface fuels present as a result of the thinning and higher wind speeds that can occur in open forests compared to those with denser canopies (Figure 44). One clear example of this comes from an area near Gold Hill that burned on September 6. The area was thinned, which allowed the high winds (Figure 28) to facilitate the burning of the slash piles scattered in the understory. These
    piles were scheduled to be burned but the burning was not complete before the Fourmile Fire occurred (Figure 45).

    The description and documentation of fuel treatments performed in the area where the Fourmile Fire burned did not describe under what weather conditions they were to be effective nor were the methods for reducing and maintaining low amounts of surface fuels (litter, grasses and herbaceous fuels) described. The amount and condition of surface fuels present in a forest is the major determinant in fire ignition, spread, and ultimate burn severity (Graham 2003, Graham and others 2004). Although activity fuels (slash or residues from thinning activities) within the Fourmile Fire were often chipped or piled for later burning, no broadcast prescribed fire was conducted. If low intensity prescribed fires would have been applied throughout the 6,000 acres 63a
    at frequent (e.g., 10 years), they would have consumed litter layers, killed shrubs and small trees (ladder fuels), and pruned the lower branches of overstory trees by scorching (Graham and others 2004, 2007). By increasing the crown base heights of trees and decreasing surface fuels the occurrence of tree torching is reduced (Figure 25).
    Based on past studies of treatment performance and under the weather conditions at the time of the fire, the surface fuel conditions in these treatments almost certainly produced high fire intensities and spread rates compared to areas where the fuels were not treated (Figures 43-45).

    Even where intensities could have been reduced by the treatments, long duration flaming
    associated with continuous surface fuels ultimately ignited and torched residual trees (Figure 31).
    Claims of fuel treatment performance around homes by the owners are consistent with the knowledge that the removal of surface fuel plays an important role in changing fire behavior.
    Evidence of these effects is seen in the live and minimally scorched tree canopies on their property after a low intensity surface fire most likely burned their property (Figure 46). Treatment units were located adjacent to roads and on ridge-lines which confounds treatment effects with those of topographically related changes in fire behavior (Figures 34, 47). Clear evidence of topographic effects is visible in the post-fire images where north-facing slopes and canyon bottoms suffered minor impacts but had received no treatment (Figures 34, 43). The slim boundary between forest consumed completely by fire and intact north facing forests is coincident with ridgelines and slope changes whether treatments were present or not (Figure 47).

    Elsewhere, (Gold Hill, Sugarloaf, Bald Mountain, Melvina Road) patterns of burn severity
    (living, scorched, and consumed conifer foliage) were found to vary independently of fuel
    treatment locations (Figures 29, 43). It is thus impossible to distinguish the various causes of burn severity, including treatment.

    High winds and the low relative humidity of the air during the Fourmile Canyon Fire are
    common weather conditions associated with all large wildfires along the Front Range foothills (Figure 2, see page 3). Thus, recognizing these conditions is critical when developing fuel treatment prescriptions. By doing so, and appropriately designing (treating surface fuels, ladder fuels, and canopy fuels in this order of importance) fuel treatments in and among landscapes in conjunction with treating fuels in the Home Ignition Zone across the Front Range, the efficacy of fuel treatments can be greatly improved (Figure 20) (Graham and others 1999, Graham 2003,
    Graham and others 2004, Graham and others 2009, Hudak and others 2011).

  3. The Report confirms that:

    1) A home’s fate depends upon fuel in its immediate surroundings and construction materials;

    2) Fuel treatments, especially those that leave fine fuels untreated, are ineffective protection against wildfires that threaten homes, i.e., windy, dry conditions; and,

    3) Fire suppression resources are easily overwhelmed precisely when Fire-Unwise homes need them the most.

    The report took a special look at aerial attack, finding that the great preponderance of retardant was dropped after the fire had already stopped advancing.


    Hey, isn’t this basically what forest activists have been saying for years? Here’s a copy of a Wildfire primer I put together back in 2004, highlighting much of the same stuff that was found in the Fourmile Canyon report.

  4. It is very typical for SW homeowners to not properly manage the fuels around their homes. In particular, shade from trees is very cherished and many landowners are unwilling to cut even a portion of the trees shading their yards. It is a similar idea that preservationists have regarding public lands. The picture above shows that there are few gaps in the forest surrounding those mansions.

    However, forests and wildfires should be managed so that small wildfires don’t travel for miles, burning in untreated forests, arriving in the WUI with such force that the minimal submerchantable fuels treatments are overwhelmed with fire intensity and fire-generated winds. Couple this with the illegal Let-Burn policy (follow the law?!?!) that allows fires to burn for weeks, and you end up with the mega-fires that do so much destruction, including homes.

    When firestorms send out spots fires far ahead of the fire front, tiny fuels treatments can be easily bypassed or burned through. The Mill Creek Incident in SW Utah is a perfect example of a fire allowed to burn for weeks, until the inevitable high winds send it out of containment, and into communities. There are no regulatory controls or public input on Let-Burn fires. When 100,000 acre wildfires are allowed, and even embraced, towns WILL be burned.

  5. This report, in the summary, does not clearly state the obvious. Under these extreme conditions of wind and extremely low humidity with a dry cold front, there is virtually nothing that can be done to suppress wildfire. That is a fact that too many landowners and the politicians don’t seem to grasp.
    Homeowners spend a million dollars on a beautiful home but too often will not spend a penny in prevention options that work. Such as fire-resistant foam or fire resistant siding and roofing. Not to mention building codes in such areas that could insist on better construction methods and materials. The report summary doesn’t delve into these factors.


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