august 2013

The 1936 fire season in Alberta was long, hot and dry and had taken its toll on men and equipment by early August. The numbers of fires, persistence needed to control and extinguish them, limited resources and long distances with little access were all factors in wearing down the fledgling Alberta Forest Service that had been established in the province just a few years earlier. Heavy smoke and haze limited visibility for the few lookouts in existence to spot new fires, and aerial patrols were non-existent.

A new start in Galatea Creek was burning, a holdover from a lightning strike a few days before. As it gained in intensity, the cry went out with the discovery of the new fire. Men and equipment were dispatched, and they fought to contain the fire as it came into the Kananaskis Valley, but it was too little, too late.

The fire erupted with blow-up conditions, jumping the breaks they were building and spotted well beyond, entrapping the crews. Tactics quickly changed as efforts doubled from trying to control the fire to survival. The fire roared northwards, past Evan Thomas Creek, over top of the Boundary Ranger station and beyond, burning most of the broad valley from rock to rock.

When fire’s growth slowed and stopped near the upper end of Skogen’s Pass, it had spread nearly 10 km down the valley and consumed more than 8,000 ha in a few short hours. Good fortune and hard work spared the men with only minor injuries. Other than timber, there were few other losses in respect to values at risk. Even the Boundary Ranger Station cabin, only a few years old, had survived.

Today’s fire challenge

Three quarters of a century later, the Kananaskis Valley is the heart of the most valued recreational area in Alberta. Hundreds of thousands of visitors flock to the area each year for day trips; to camp in the large developed campgrounds and remote backcountry campsites; or to stay in the comfort of five-star hotels and spas. They golf, hike, tour, fish, climb or engage in any one of dozens of outdoor pursuits. With access through countless trails, visitors can be found in the most remote parts of the valley and the various steep drainages that feed into the Kananaskis watershed. Highway 40, the single access in and out of the valley, is heavily used by these visitors.

In 1936, the vegetation cover in the valley was a mosaic created from numerous fires over the years, many of which were from aboriginal burning prior to European settlement. Today, the vegetation cover is largely a continuous Lodgepole pine fuel type that grew in undisturbed since the 1936 fire. Most of the lands within the valley are now managed by Tourism, Parks and Recreation (TPR), but fire management and suppression remain the responsibility of Environment and Sustainable Resource Development (ESRD), the successors to the old Alberta Forest Service.

With recent fire regime studies and a better understanding of past fire history and disturbance trends, both agencies recognize the need for ecological restoration, fuel reduction and the value of strategic breaks in the fuels in the valley. A number of projects were identified in the valley, but putting disturbances back on the landscape is not necessarily an easy process.

TPR’s mandate is to protect the province’s natural landscapes in Alberta, but the use of mechanical equipment or logging to remove the trees is limited. Prescribed fire was considered to be an acceptable alternative, as fire has been both a natural and anthropogenic process in the valley. The problem faced by fire managers was how to safely create a high-intensity, low-severity, stand replacement fire within the continuous, homogenous fuel type that now exists through the entire valley with the limited use of mechanical equipment.

Usually with interagency planning processes, challenges and conflicts would be expected due to different cultures, mandates and perspectives of agencies. Recognizing that both agencies desired the same outcomes, staff from both ESRD and TPR used the planning process as an opportunity, rather than a challenge, to broaden each agency’s outlook, share its skills and learn from each other.

Designing a 21st century prescribed burn

The Evan Thomas prescribed burn was chosen as the first of several vegetation management projects identified within the Kananaskis Valley. Its objectives included creating a landscape level fire break, improving elk habitat, restoring goat habitat, restoring age class diversity, etc. However, putting a large (400+ ha), high-intensity stand replacement fire on the landscape with so much development in the area was a major concern.

The solution was to reverse engineer what is already done in the wildland urban interface (WUI): fuel modification. In the WUI, fuel modification (thinning, removing dead and down fuel, pruning, etc.) is commonly used to reduce fuel loads in an effort to minimize fire intensities near communities. In this case, we wanted to increase the surface fuels inside the burn unit to improve the flammability of the fuels within the burn unit itself. This would provide a fire behavior response of higher intensity fire in lower fire danger indices, thus decreasing the risk of the prescribed fire escaping and threatening the numerous values within the valley.

To avoid confusion with the term “fuel modification,” which is synonymous with fuel reduction and the WUI, the term “fuel amendment” was used to describe the process. Fuel amendment simply refers to increasing stand flammability by adding to, or increasing, the surface fuel load of the stand.

The design of the burn unit took advantage of topographic changes. Evan Thomas Creek was used as the boundary on the bottom end. Two small tributary creeks were used as boundaries along the sides of the burn unit, and the top of the burn unit was capped off with an Alpine meadow. Within the main burn unit, an objective of falling from 10% to 30% of the stems within the stand was established. This would increase the slash loading at ground level and, after a short period of curing, would increase the flammability within the burn unit. In addition, by opening up the forest canopy, the forest floor becomes more open to sunlight and wind, which helps to dry the stand quicker. The range of 10%-30% reduction would help to ascertain how much fuel amendment was necessary to achieve a response in lower indices.

While using mechanized equipment within the provincial park is very restricted, it was agreed that a feller buncher could be utilized to fall the trees. This would both expedite the process as well as provide an increased safety margin over hand falling on steeper slopes.

During the planning process, several operational concerns for the fuel amendment were noted. Although the use of the feller buncher was permitted, if there were indications of rutting or excessive ground disturbance, operations would cease. Buffers would be required along creeks as well as a recreational trail that went through the center of the burn unit along the Evan Thomas Valley. Cross-slope openings would need to be left to maintain wildlife travel corridors.

Burn operations would also face restrictions. The presence of a nearby resident mountain goat herd meant no burning from mid-May to mid- June to lessen the disturbance to the animals during kidding season. Heavy recreational use occurred through July and August, and fall hunting would also be affected. Smoke management was a concern within the immediate area but also eastwards towards Calgary. Planners linked in and worked closely with the Calgary Regional Air Zone, a committee established by local municipalities to manage air quality in the region. Communication strategies and plans related to the burn were designed to be inclusive so that anyone on the list would be advised of all operational activities.

Prior to the commencement of the fuel amendment, plots were estab- lished to determine the location of existing pre-disturbance fuel loads. A tracked feller buncher was used for the fuel amendment. Once operations began, the team found that it could operate the buncher parallel to the slope but could not effectively operate cross slope with any efficiency.

A decision was made to use the buncher to cut strips going up the slope with varied widths between the strips to achieve the 10%-to-30% objective. In addition, the operator varied the cutting pattern by either leaving the cut trees within the cut strip or laying them alternatively into either side within the leave strips.

Attention to resource values was core to the fuel amendment process. Leaving wildlife travel corridors was simplified by flagging the corridor locations, and the operator could ensure that they were not blocked by slash during the felling operation. Buffers along both sides of the trail and watercourses were also flagged and then pre-cut on the outside of the buffers early in the operation. No rutting or excessive ground disturbance occurred during the operation.

Altogether, the fuel amendment process took approximately four weeks during the late winter/early spring. The fuel loading plots were re-measured after the fuel amendment and determined that fine coarse woody debris had increased between 7 to 15 tonnes per ha.

Determining what indices and conditions under which the burn unit could be safely burnt became an issue with fuel amendment. By applying fuel amendment to the burn unit, the fuel type changed, as well. The Canadian Forest Fire Behavior Prediction System uses fuel types that have been developed through years of field research and plot burning. The fuel type for a mature Lodgepole pine stand is a C3 fuel type, and pine slash in a cut block is an S1 fuel type. Both fuel types have a significantly different response.

“Blending” or “merging” the two fuel types to try to come up with a new fuel type is at best a guess. To solve the problem, reverse engineering was used again. Rather than try to “guesstimate” the indices needed to ignite the burn unit safely, matrixes were developed using the less flammable surrounding C3 fuel type as well as indices that would be needed to make it respond. By burning in lower indices, the more flammable fuel-amended burn unit could be burnt safely with little chance of escape.

The summer burn window

Some drying and curing of the slash was necessary to ensure a good response from the amended fuels. It was decided that no burning would occur until the fuels had at least four months to cure. A burning window briefly presented itself in early September, but an unexpected heavy rain shower hit the burn unit just moments before ignition was to commence.

Cooler and wetter weather dominated the fall, leaving no options for burning. Heavy snow over winter and a late spring eliminated any potential for a spring burn, as well. By early summer, the concern was that the needles on the slash were now start- ing to drop. If burn operations were not completed before winter, the slash loads would start to decrease through a loss of the fine fuels. It was agreed that with consultation to local stake- holders and with good public communications, burning could occur in August, outside of long weekends, with the temporary closure of the area.

In early August, a suitable burn window presented itself. During the weekend, crews and equipment were deployed and set up in preparation for the burn. Researchers completed the final measurements of the fuel loading plots, in-burn cameras were set up and the area was closed to the general public. The burn unit and surrounding areas were flown over to ensure that no people or ungulates were within the burn unit and surrounding areas.

In early August of 2011, almost 75 years to the day of the 1936 fire, aerial ignition operations commenced. The temperature was 23 C, RH 26% with winds W at 6 km. The first test ignition drops occurred in non-amended fuels to validate that limited spread would occur in that fuel type. Operations then progressed to the main burn unit starting on the upper slopes and work- ing downwards with two helicopters with aerial ignition torches.

Fire behavior within the amended fuels varied between a very hot surface fire with torching to a continuous crown fire. As expected, some runs above the amended fuels occurred on the steeper slopes (Engelmann Spruce/ Lodgepole Pine) to the Alpine areas. Minimal surface spread occurred from the edge of the fuel-amended areas, and no spot ignitions were observed outside of the main burn unit. Limited spread downslope along a southeast-facing slope occurred, but it self-extinguished.

Ignition operations progressed, moving back and forth across the slope until they reached the bottom end of the ignition unit along Evan Thomas Creek. Most of the burn unit was completed by the end of the first day, with burn operations continuing for a second day in an effort to clean up small patches of unburnt fuels. Crews that had been deployed in readiness to contain the burn if necessary were assigned to mop up the burn itself to reduce the potential impacts of smoldering and smoke.

A successful burn

By every standard, the Evan Thomas prescribed burn was a success. A high-intensity fire burnt through the main burn unit resulting in an estimated 80% mortality. Under the lower burnt indices, the surrounding homogenous fuels would not respond, creating a very safe environment in which to conduct a prescribed burn.

Post-burn measurements within the plots demonstrated significant consumption of the fine-to-medium fuels with low severity effects. With the burn being central to a highly valued recreational landscape, the visibility to the general public was very high and resulted in excellent lessons of the safe use of fire.

There is little doubt that wildland managers are feeling the effects of change. Climate is changing; with
it, our aging forests are in declining health and increasing flammability. The public purse is limited, and values at risk continue to skyrocket. Implementing new concepts and new tools such as fuel amendment is necessary to avoid disasters in the future.