Canada’s Fire Behaviour Prediction System

Canada’s Fire Behaviour Prediction (FBP) System is a systematic method for assessing the potential of wildland fire behaviour. It is part of the Canadian Forest Fire Danger Rating System (CFFDRS).

View fire behaviour maps on the Canadian Wildland Fire Information System (CWFIS).

Wildland fire managers use the FBP System, in combination with their experience, as part of their decision-making process.

Inputs to the FBP System include factors that have an impact on wildland fire behaviour, such as:

• vegetation fuel type
• wind
• fuel moisture
• topography

Outputs of the FBP System provide numerical estimates for:

• potential head fire spread rate (how fast a fire will grow)
• fuel consumption (how much fuel will burn)
• fire intensity (how high the flames could be)
• fire description (the type of fire expected – surface fire or crown fire)

Using an elliptical fire growth model, the FBP System gives estimates of:

• fire area
• fire perimeter
• perimeter growth rate
• fire behaviour at the head, flanks and back of a wildland fire

Text version

14 primary data inputs are used by the FBP System to mathematically develop 4 primary and 11 secondary outputs.

Primary inputs include:

• wind (speed, direction)
• fuels (FBP system fuel types)
• Fire Weather Index (FFMC, ISI, BUI)
• topography (percent slope, slope direction)
• foliar moisture content (elevation, latitude / longitude, date)
• type and duration of prediction (elapsed time, point or line ignition).

Primary outputs are generally based on a fire intensity equation, include:

• rate of spread
• fuel consumption
• head fire intensity
• fire description

Secondary outputs, calculated using a simple elliptical fire growth model, include:

• head, flank and back fire spread distance
• flank and back fire rates of spread
• flank and back fire intensities
• elliptical fire area and perimeter
• rate of perimeter growth
• length-to-breadth ratio

FBP System inputs

Primary data inputs generally describe the physical environment a wildland fire might be spreading in:

• fuel (16 general fuel types that represent most of the major fuel types in Canada)
• weather (including outputs from Canada’s Fire Weather Index (FWI) System) and wind
• topography (percent slope and direction [aspect])
• location and time of year dictate a forest’s seasonal state, such as leaf emergence
• ignition type and time since ignition

FBP System outputs

There are four primary and eleven secondary outputs of the FBP System:

Primary outputs

Rate of Spread (ROS): the predicted speed of a wildland fire at its front or head (the direction it is spreading fastest)

• measured in meters per minute (m/min)
• is based on the fuel type, Initial Spread Index (ISI), Buildup Index (BUI) and several fuel-specific parameters such as:
  • phenological state (leafless or green) in deciduous trees
  • crown base height in coniferous trees
  • percent curing in grasses
• allows for crowning and spotting

Total Fuel Consumption (TFC): the amount of fuel expected to be consumed by a fire

• measured in kilograms per square meter of ground surface (kg/m² of ground surface)
• includes fuels consumed both on the surface and in the canopy of the forest
• TFC is also used to calculate the release of carbon and greenhouse gases from wildland fires

Head Fire Intensity (HFI): the estimated energy output at the head or front of the fire (the direction the fire is spreading fastest)

• measured in kilowatts per meter of fire front (kW/m of fire front
• based on ROS and TFC
• is strongly related to flame size
• used in many parts of the world as a standard indicator for estimating the difficulty of controlling a fire and selecting appropriate suppression methods

Fire description:

Crown Fraction Burned (CFB): the estimated fraction of the forest canopy consumed by the passage of a wildland fire

• based on Buildup Index, Foliar Moisture Content, Surface Fuel Consumption and ROS

Fire Type (FT): provides a general description of the wildland fire.

• FT is based on the CFB and is used to predict if the fire will be a:
  • surface fire
  • continuous crown fire
  • intermittent crown fire

Secondary outputs

• head, flank and back fire spread distances
• flank and back fire rates of spread
• flank and back fire intensities
• elliptical fire area and perimeter
• perimeter growth rate
• length-to-breadth ratio