The South Canyon Fire

The South Canyon Fire was started by a lightning strike on the afternoon of 2 July 1994. For the next 2 days the fire burned downslope. By 12.00 noon on the 4 July the fire had burned approximately 3 acres. It continued to burn downslope through the day of 5 July, covering around 50 acres by the end of the day. General fire activity consisted of low intensity downslope spread with intermittent flare-ups and short duration upslope runs in the fire’s interior. The fire remained active through the night covering approximately 127 acres by the morning of 6 July.

At around 3.20pm on the afternoon of 6 July a dry cold front passed over the area. At about 4.00pm and for the next four hours the fire burned generally north and east through shrub and tree canopies as a fast moving wind-driven front. It exhibited dramatically greater rates of spread, flame heights and energy release rates than at any time since its ignition.

The South Canyon Fire eventually burned 2,115 acres and was declared controlled on the 11 July 1994. This fire will not be remembered for the acreage burned but for the lives lost. On the afternoon of 6 July, fire entrapped and killed 14 firefighters, making the fire one of the most tragic wildland fires to occur in the United States this century.

In September 1998 a report on the “Fire Behaviour Associated with the 1994 South Canyon Fire on Storm Mountain, Colorado” was published by the US Forest Service.

The Study focused on two events: the “blowup” or the transition from surface fire to a fire burning through the shrub canopy; and the behaviour in the area identified as the West Flank where the 14 firefighters died.

The Report identified a number of discussion points:

1. Topography can dramatically influence local wind patterns. Surface winds in mountainous terrain are highly variable. Areas of low or calm winds can exist while other areas experience dramatically different wind direction, windspeed or both. These changes can occur without visible warning across relatively short distances, especially when the area is subjected to large scale weather influences such as frontal passages. Wind information is needed from multiple locations around the fire perimeter. This information should be communicated to all fire personnel.
   
2. Vegetation and topography can reduce a firefighter’s ability to see a fire or other influencing factors. Complex topography and dense shrub or tree canopies can restrict the ability of firefighters to sense, visually or otherwise, changes in wind, fire behaviour and fire location.
   
3. Current and past fire behaviour often does not indicate the potential fire behaviour that could occur.
   
4. The longer a fire burns and the larger it gets, the greater the likelihood of high intensity fire behaviour at some location around the perimeter. Not always is a fire ignited in an ideal location for high intensity burning. However given sufficient time, a low intensity fire will often reach a position where fuel, weather and terrain combine synergistically to produce high intensity fire behaviour.
   
5. The transition from a slow spreading, low intensity fire to a fast moving, high intensity fire often occurs rapidly. This seems to surprise firefighters most often in live fuels, possibly because green vegetation is associated with reduced ignition risk. Live green vegetation can support and even promote high intensity burning. Monitoring fire position relative to alignment of wind, slope, live and dead fuels can assist firefighters in recognizing potentially hazardous fire behaviour.
   
6. Escape route transit times is related to both topography and route length.The ideal escape route includes a downhill direction over the shortest possible distance to the safety zone, thereby maximizing firefighter travel rates while minimizing fire spread rates.
   
7. Smoke can significantly reduce the firefighter’s abilities to sense changes in fire behaviour.

   The analysis emphasizes the often dramatic changes in fire behaviour that can occur when fire is exposed to steep slopes, winds and relatively continuous fuels. Perhaps more important is the observation that not all of these factors are needed, rather only one or two are needed for a blowup to occur.

   None of the findings and observations discussed in this study represent new breakthroughs in wildland fire behaviour understanding. Rather the findings support the need for increased understanding of the relations between the fire environment and fire behaviour. We can also conclude that fire managers must continue to monitor and assess both present fire behaviour and potential future fire behaviour given the possible range of environmental factors.

   Extract from:
   “Fire Behaviour Associated with the 1994 South Canyon Fire on Storm King Mountain, Colorado”

   By
   Bret W. Butler, Roberta A. Bartlette, Larry S. Bradshaw, Jack D. Cohen, Patricia L. Andrews, Ted Putnam, Richard J. Mangan from the Intermountain Fire Science Lab and the Missoula Technology & Development Center in Missoula, Montana.