Canada: Wildfire – Rating the Threat   (IFFN No. 18 – January 1998)


Wildfire – Rating the Threat

(IFFN No. 18 – January 1998, p. 82-83)

A Wildfire Threat Rating System (W.T.R.S.) has been developed for the McGregor Model Forest near Prince George, British Columbia, Canada. It provides forest resource managers with the knowledge to assess where and how fires are a potential threat and allows the exploration of fire management options. When this fire management planning system is coupled with a forest management planning system, it can be used to determine the wildfire threat associated with alternative forest management plans.

“A shift to alternative silviculture techniques means the landscape is changing as well as the fuel complex, which means the wildfire threat has also changed,” said Brad Hawkes, fire research officer in the Fire Network of the Canadian Forest Service. “The W.T.R.S. will help us determine how different land use decisions will affect the wildfire threat in a given area.”

Although the W.T.R.S. will be essential to determining how the wildfire threat is affected by various silvicultural techniques, its immediate use is as a tool for managing wildfires. The concerns of a fire manager include: What is the potential for fire ignition; what are the values at risk (potential loss of life, property, timber supply, aesthetic values); what is the potential wildfire behaviour; and how easily could it be suppressed? The W.T.R.S. compiles these factors to create an overall wildfire threat for a specific area.

“With GIS and the accompanying analysis system, we are able to look at many variables at once and understand how they operate together,” explained Hawkes. “With such information we can make predictions for future scenarios to determine which factors would lead to, or avoid, a wildfire in the area.”

Forest inventory information about the McGregor Model Forest was coupled with silviculture information to create a fuel-type map for the area. This map was overlaid with digital terrain information to determine slope and aspect which affects fire behaviour. Details such as rate of spread, fire intensity and potential for crowning were combined into another map. The suppression capability was calculated by considering such factors as access to water supplies and characteristics of the landscape. Finally, the values at risk were added into the equation. Each of these components were weighed equally to come up with an overall wildfire threat.

The McGregor Model Forest is valued by local communities for its employment, forest products, recreation, scenic qualities, ecological features, and cultural values. The 181,000 hectares of rolling plateaus and abundant wetlands (with some mountainous terrain) are dominated by spruce and alpine fir. The forest has two main rivers and has been affected by timber harvesting, wildfire, defoliating insects, bark beetles, disease, wind throw, and floods.

“It was found that although the McGregor Model Forest as a whole has a moderate to high overall wildfire threat, there were many areas that rated a much lower threat,” said Hawkes. “Knowing what part of the forest is under the greatest threat allows the fire manager to assess potential fires in a strategic manner. For example, before fire season begins, the fire manager would be able to determine the optimal place to position fire-fighting resources.”

The Wildfire Threat Rating System was first introduced in Australia but its application to the McGregor Model Forest was a collaborative effort between the Canadian Forest Service, the B.C. Ministry of Forests and the McGregor Model Forest. The area is one of ten Canadian model forests established by the Government of Canada to provide sites to demonstrate sustainable development.

This article is taken from Information Forestry, April 1997 issue, Natural Resources Canada, Canadian Forest Service, Pacific Forestry Centre, Victoria, British Columbia, Canada.

Citation: Hawkes, B., J.Beck, and W. Sahle. 1997. A wildfire threat rating system for the McGregor Model Forest. Final Report for the McGregor Model Forest, Prince George, B.C. (contains 5 sections, Conference Paper, Feedback Workshop, GIS Documentation, Fuel Type Photo Series, and Wildfire Threat Maps).

Retrospective Fire Study

A retrospective study of fire was initiated in the north-eastern interior of British Columbia, Canada as a part of the McGregor Model Forest Association’s larger goal to determine the ecological processes that influence the forest landscape in this area. The area of study encompassed approximately 1.3 million hectares of forested and mountainous terrain stretching along the western side of the Rocky Mountains within the Sub-Boreal Spruce (SBSvk), Engelmann Spruce Subalpine Fir (ESSFwk2), and Engelmann Spruce Subalpine Fir (SBSwc3) biogeoclimatic units. British Columbia Ministry of Forests digital forest inventory data was heavily relied upon to determine the age and patch characteristics of the study landscape. Using this data the objectives have been to address the knowledge gap regarding the historical fire regime in the study area. Estimates have been derived of historical patch size, patch shape, and rate of disturbance in the study landscape. Analysis has also included comparison of historical patch size estimates with fire records for the period of 1950-1992, as well as an examination of the seasonality of fire occurrence for both natural and human-caused fires in this time period. Results of some sample plot data collected within the study area are also presented.

Results indicated that the fire cycle for these cool and wet mountainous subzones seems to be much longer than initially estimated and that both the SBSvk and ESSFwk2/wc3 biogeoclimatic units should be classified as Natural Disturbance Type 1 systems (rare stand-initiating events) in the provincial Biodiversity Guidebook. Patch sizes within the study area exhibit a north-south difference with the northern half of the study area characterized by larger disturbance patches than the southern half of the study area. It appears as though the importance of very large patches in this landscape is underestimated in the Biodiversity Guidebook. Patch shape complexity differs significantly between the northern and southern sections of the study area. It is likely that the higher proportion of very large patches in the northern portion of the study area is contributing to this north-south difference.

Citation: Hawkes, B., W.Vasbinder, and C.Delong. 1997. Retrospective fire study. Final report for the McGregor Model Forest Association. McGregor Model Forest, Prince George, B.C., 35p. (includes age class map).

Contact Information: Brad Hawkes can be reached by e-mail: A technology transfer note is available for the Wildfire Threat Rating System project from the author. Information about the Pacific Forestry Centre can be obtained from the World Wide Web at: and information about the Canadian Forest Service Fire Management Network can be obtained from the World Wide Web at:

The final reports of both studies are now available on the McGregor Model Forest Web Site at:

They can be downloaded and/or printed using the ACROBAT READER in NETSCAPE. If one does not have this add-on program with Netscape there is a hot button on the MMFA web site to download a copy to view this report. If you have a colour printer, then a colour version of the figures can be printed. It can be viewed in colour with the reader.

Information on the McGregor Model Forest can be obtained at the following address:



From: Bruce MacArthur
McGregor Model Forest
 Northwood Forest Centre
P.O. Box 9000
Prince George, B.C. V2L 4W2

Fax: ++1-250-962-3364
Tel:  ++1-250-962-3467

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