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Wildfire Analyst Fire Weather / Fire Behavior Glossary

Fire Behavior Index

Technosylva Metric: Fire Behavior Index

Comparable Canadian Metric: Head Fire Intensity

Comparable Canadian Metric - Definition: The Fire Behavior Index (FBI) is computed using the average Flame Length and Rate of Spread at the fire front over the entire 8-hour unsuppressed fire simulation. It is derived from the fire’s Rate of Spread (meters per minute) and Flame Length (meters). These values are directly related to suppression activities, as summarized in the commonly used Hauling Chart or classified into intensity levels from 1 to 5. FBI describes how large and fast-moving the flames are over the burn duration.

The closest Canadian equivalent is Head Fire Intensity (HFI), which quantifies fire severity and its impact on suppression efforts. HFI is calculated using the rate of spread, fuel consumption, and heat of combustion, expressed in kilowatts per meter (kW/m). Like FBI, HFI can be categorized into threshold-based fire intensity classes to support fire behavior assessments and operational safety measures. However, the thresholds differ between the two systems due to variations in fuel types and the specific environments they represent.

Fire Size Potential

Technosylva Metric: Fire Size Potential

Comparable Canadian Metric: Fire Size Potential

Comparable Canadian Metric - Definition: Total simulation size in hectares. The Fire Size Potential represents the actual simulated hectares of a fire based on the local fuels, weather, and terrain starting from an ignition at a specific location and time.

Rate of Spread

Technosylva Metric: Rate of Spread

Comparable Canadian Metric: Rate of Spread

Comparable Canadian Metric - Definition: The speed with which the fire is moving away from the site of origin. Calculated as an average value at the front of the fire.

Flame Length

Technosylva Metric: Flame Length

Comparable Canadian Metric: Flame Length

Comparable Canadian Metric - Definition: The distance measured from the average flame tip to the middle of the flaming zone at the base of the fire. Calculated as an average value at the front of the fire.

Response Complexity

Technosylva Metric: Response Complexity

Comparable Canadian Metric: Fire Type

Comparable Canadian Metric - Definition: The distance measured from the average flame tip to the middle of the flaming zone at the base of the fire. Calculated as an average value at the front of the fire.

Buildings Threatened

Technosylva Metric: Buildings Threatened

Comparable Canadian Metric: Buildings Threatened

Comparable Canadian Metric - Definition: Total number of buildings threatened by the simulation footprint. (Accuracy is datasource dependent)

Population Impacted

Technosylva Metric: Population Impacted

Comparable Canadian Metric: Population Impacted

Comparable Canadian Metric - Definition: Total population impacted by the simulation footprint. (Accuracy is datasource dependent).

Initial Attack Assessment

Technosylva Metric: Initial Attack Assessment

Comparable Canadian Metric: N/A

Comparable Canadian Metric - Definition: Provides an estimation of the difficulty of fire control in the first 1-2 hours after ignition time, ranging from 1 to 5. The higher the value, the more likely the fire is to escape the initial response, ending in a potential threat.

Moisture 100h

Technosylva Metric: Moisture 100h

Comparable Canadian Metric: Duff Moisture Code(DMC)

Comparable Canadian Metric - Definition: 100-hour fuels are standard dead fuels with diameters ranging from 1 to 3 inches (~2–7 cm). Due to their larger size, the moisture content of 100-hour fuels responds more slowly to changing weather conditions. These fuels can also serve as an indicator of the average moisture content of the forest floor. 100-hour fuel moisture is expressed as a percentage, where lower values indicate drier conditions.

In Canada, the closest equivalent is the Duff Moisture Code (DMC). While both track moisture in medium-sized fuels, DMC is more general and not tied to specific fuel types. It represents the moisture content of decomposed organic material beneath the litter, as well as fuels of similar size (~2–7 cm), with a 15-day (360-hour) time lag. Unlike 100-hour fuel moisture, which is measured as a percentage, the DMC is a unitless, open-ended index where higher values correspond to drier conditions.

Moisture 10h

Technosylva Metric: Moisture 10h

Comparable Canadian Metric: Fine Fuel Moisture Code (FFMC)

Comparable Canadian Metric - Definition: 100-hour fuels are standard dead fuels with diameters ranging from 1 to 3 inches (~2–7 cm). Due to their larger size, the moisture content of 100-hour fuels responds more slowly to changing weather conditions. These fuels can also serve as an indicator of the average moisture content of the forest floor. 100-hour fuel moisture is expressed as a percentage, where lower values indicate drier conditions.

In Canada, the closest equivalent is the Duff Moisture Code (DMC). While both track moisture in medium-sized fuels, DMC is more general and not tied to specific fuel types. It represents the moisture content of decomposed organic material beneath the litter, as well as fuels of similar size (~2–7 cm), with a 15-day (360-hour) time lag. Unlike 100-hour fuel moisture, which is measured as a percentage, the DMC is a unitless, open-ended index where higher values correspond to drier conditions.

Moisture 1h

Technosylva Metric: Moisture 1h

Comparable Canadian Metric: Hourly Fine Fuel Moisture Code (HFFMC)

Comparable Canadian Metric - Definition: 1-hour fuels are fine dead fuels with diameters less than 0.25 inches (~0.64 cm), such as grasses. The moisture content of 1-hour fuels responds rapidly, changing within minutes to an hour based on weather conditions. 1-hour fuel moisture is expressed as a percentage, where lower values indicate drier conditions.

In Canada, the closest equivalent is the Hourly Fine Fuel Moisture Code (HFFMC). Like 1-hour fuel moisture, HFFMC tracks the moisture of small, fast-drying fuels over a similar time interval. However, HFFMC is more general and not tied to specific fuel types, instead representing fine surface fuels within a soil depth of 0–2 cm. Unlike 1-hour fuel moisture, which is measured as a percentage, HFFMC is a unitless index where higher values correspond to drier conditions.

Woody LFM

Technosylva Metric: Woody LFM

Comparable Canadian Metric: Foliar Moisture Content (FMC)

Comparable Canadian Metric - Definition: Woody Fuel Moisture influences both the flammability of living woody vegetation and the transfer of living woody fuel loads from and to dead 1-hour Time Lag (Moisture 1h) fine fuels. The metric is presented as a percentage, with lower values indicating drier woody live fuels.

The closest Canadian equivalent is Foliar Moisture Content (FMC), which represents the moisture content of conifer needles in tree crowns. However, FMC is more general and is estimated based on the time of year and geographic location, specifically elevation and latitude, rather than direct measurements. Woody Fuel Moisture is influenced by vegetation type, seasonal changes, temperature, humidity, precipitation, and geographic factors such as solar exposure.

Herbaceous LFM

Technosylva Metric: Herbaceous LFM

Comparable Canadian Metric: Grass Curing

Comparable Canadian Metric - Definition: Herbaceous Fuel Moisture influences both the flammability of living herbaceous vegetation and the transfer of living herbaceous fuel loads from and to dead 1-hour Time Lag (Moisture 1h) fine fuels. The metric is presented as a percentage, with lower values indicating drier herbaceous fuels.

The closest Canadian equivalent is Grass Curing (FMC), which is represented as a simple coefficient or scalar based on the time of year. In contrast, Herbaceous Fuel Moisture is influenced by vegetation type, seasonal changes, temperature, humidity, precipitation, and geographic factors such as solar exposure.

Ignition Probability

Technosylva Metric: Ignition Probability

Comparable Canadian Metric: Probability of Sustained Ignition

Comparable Canadian Metric - Definition: The likelihood that a live ember or firebrand will successfully ignite a fuel bed when it lands on it, primarily determined by the current fuel moisture content, air temperature, and the amount of shading from canopy cover or clouds, essentially representing the chance of a spark starting a fire under specific environmental conditions.

Spread Component

Technosylva Metric: Spread Component

Comparable Canadian Metric: Initial Spread Index

Comparable Canadian Metric - Definition: Spread Component (SC) is a rating of the forward rate of spread of a head fire. It integrates the effects of wind, slope, fuel bed characteristics, and fuel particle properties. Daily variations occur due to changes in wind and moisture content in live fuels, as well as in the 1-hour, 10-hour, and 100-hour dead fuel time lag classes. Higher SC values correspond to faster spread rates.

The closest Canadian equivalent is the Initial Spread Index (ISI). ISI is more general than SC, as it does not account for fuel types or ground slope—those factors are instead considered in the Rate of Spread (ROS) within the Fire Behavior Prediction (FBP) system. However, ISI is similar in that it incorporates wind and surface fuel moisture to estimate the expected spread rate at the head of a fire, with higher values indicating faster spread rates.

Energy Released Component

Technosylva Metric: Energy Released Component

Comparable Canadian Metric: Build Up Index

Comparable Canadian Metric - Definition: Energy Release Component (ERC) represents the estimated potential energy released per unit area in the flaming zone of a fire. It depends on the same fuel characteristics as the Spread Component (SC), but with a greater emphasis on fuel moisture. Daily variations in ERC are driven by changes in moisture content across various fuel classes, including the 1000-hour time lag class. ERC is derived from predictions of the rate of heat release per unit area during flaming combustion and the duration of burning, and it is expressed in BTUs per square foot.

The closest Canadian equivalent is the Buildup Index (BUI). BUI combines the Duff Moisture Code (DMC, ~100-hr fuels) and the Drought Code (DC, ~1000-hr fuels) to estimate the potential heat released by a fire if it were to ignite. While BUI is more general than ERC, as it does not account for specific fuel types, both metrics are similar in that higher values indicate greater potential heat energy release.

Click here for more information on the CFFDRS

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