The Canadian Forest Fire Danger Rating System
During the forest fire season in Canada, hundreds of fires may be burning at any one time, started by lightning strikes and human activity. Not every fire needs to be extinguished. Many will burn themselves out or be put out by wet weather. And not every fire can be extinguished, because firefighting resources are limited.
It is the job of fire managers to assess which fires pose a threat to human safety, property and public assets (including homes, businesses, utility corridors, wildlife and merchantable timber) and to then decide what fire-fighting resources are needed and where. In making such decisions, these managers use both their personal experience and information provided by the Canadian Forest Fire Danger Rating System (CFFDRS).
The CFFDRS is the principal source of fire intelligence for all forest fire management agencies in Canada. It is also the most widely applied fire danger rating system in the world.
The CFFDRS’s development over time
Research that combines meteorological observation, field sampling of moisture from various fuel types and fuel layers, and small-scale test fires begins at the Petawawa Forest Experiment Station near Chalk River, Ontario. Focus is on pine and hardwood forest types.
1940s to early 1960s
Research program expands to include all major forest types across Canada.
Fire hazard and fire danger tables are developed for various regions in Canada.
mid- to late 1960s
A universal system of common indices to support the sharing of firefighting resources is proposed.
A fire danger working group, made up of Canadian Forest Service (CFS) fire researchers from across the country, is formed to guide development of what is still the CFFDRS in use today.
The two main parts of the CFFDRS
The Canadian Forest Fire Weather Index (FWI) System, which depends solely on weather readings, provides a general measure of fire danger throughout forested and rural areas. The codes and indices of this system are calculated based on a single “standard” forest fuel type (mostly jack pine and lodgepole pine).
Fire managers use the FWI System to anticipate the potential for daily fire ignition across the landscape, considering fires in two distinct categories:
- Human-caused fire – The likelihood of human-caused fire occurring in an area on a particular day can be predicted based on: 1) how receptive the small, thin forest fuels are to ignition and spread (largely determined by the moisture content of these surface fuels); and 2) how much human activity is happening in or near the forest (creating “ignition sources”). Clear patterns of this activity can appear, with fires emerging in clusters close to populated areas, roads and railways.
- Lightning-caused fire – Fire managers track the location of all the lightning strikes in their regions, in real time, every day of the fire season. They use this information, along with outputs from the FWI System, to tell them where pockets of lightning-caused fire can be expected to hold over (grow slowly beneath the surface or in dry rotten logs) and when lightning-caused fires might begin actively spreading.
The Canadian Forest Fire Behavior Prediction (FBP) System helps forest managers assess how fast a specific fire could spread in a particular forest type, how much fuel it might consume and, ultimately, how intense that fire might be. The intensity of a fire is the factor a fire manager uses to determine what tactics and resources are needed to fight a fire.
The FBP system relies on 14 primary data inputs in five general categories: fuels, weather, topography, foliar moisture content, and type and duration of prediction. This data, when combined, provides an indication of expected fire behaviour. For example, the moisture content of surface fuels, together with the observed wind speed, yields the Initial Spread Index—an indicator of how fast a fire is expected to spread—which in turn is used to calculate a fire’s rate of spread (e.g., in kilometres per hour).
The FBP System also uses the indices of the Forest Fire Weather Index System and converts them to stand-specific predictions of fire behaviour for all the major forest types across Canada.
International uptake of the CFFDRS
The CFFDRS and the CFS’s related information products have led to Canada being recognized globally as a leader in fire science and in fire management expertise.
This rating system has been fully implemented in parts of the U.S. and in New Zealand, and components of it have been used in many countries, including Spain, Portugal, Sweden, Argentina, Mexico, Fiji, Indonesia and Malaysia.
The CFFDRS is popular because it:
- is relatively simple to use;
- can be adapted to a variety of environments; and
- includes many interpretation aids (such as posters, reference tables, and electronic data-processing and display systems) that support a variety of situations.
The future of the CFFDRS
The decision-making environment for wildfire managers has changed considerably in recent decades. Of key concern is that the extent of the wildland–urban interface has grown, putting more communities as well as more natural resources at risk. Advances in remote sensing, greater use of information technology and the increasing rapidity of communication have all helped put more detailed and more up-to-date information in the hands of fire managers.
Through continued fire research, the CFFDRS is evolving and incorporating these new sources of information, in this way providing fire managers with an accurate description of ever-changing fire environment.
Despite the changes in forest fire management since the CFFDRS was adopted, the system today remains the main information tool used by fire agencies to forecast the potential impacts of a shifting climate on fire hazard, and to develop appropriate adaptation strategies.
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