Grass Model

The grass fuel model (NFDRS fuel model L) is a numerical formula that represents wildfire behavior in grasses such as those found in old fields, and is typical of spring fires in Minnesota.

**Local agency personnel should contact MNCC Fire Intelligence if errors or omissions are observed.**

Grass ic o medium Ignition Component
(spring season indicator)
Grass ic legend
Grass ic f medium
Grass bi o medium Burning Index
(spring season indicator)
Grass bi legend
Grass bi f medium
Grass sc o medium Spread Component
(spring season indicator)
Grass sc legend
Grass sc f medium
Grass ec o medium Energy Release
Grass ec legend
Grass ec f medium
Grass th o medium Thousand-Hour Fuels
Grass th legend
Grass th f medium


The fire behavior index maps are output from computer models based on weather data reported at weather stations located across the state. Two sets of fire indices are available - observed indices represent the potential worst-case burning conditions for the current day, while forecasted indices show predicted worst-case burning conditions for the following day.

Ignition Component (IC)

Ignition Component relates the probability that a fire requiring suppression action will result if a firebrand is introduced into a fine fuel complex. The ignition component can range from 0 when conditions are cool and damp, to 100 on days when the weather is dry and windy. Theoretically, on a day when the ignition component registers a 60, approximately 60% of all fire brands that come into contact with wildland fuels will require suppression action.

Spread Component (SC)

Spread Component (SC) is the forward rate of spread at the head of the fire in feet per minute in a given fuel model. The inputs required to calculate the SC are wind speed, slope, fine fuel moisture (including the effects of green herbaceous plants), and the moisture content of the foliage and twigs of living, woody plants.

Energy Release Component (ERC)

Energy Release Component is a calculated field which provides a relative index of the amount of heat (in BTUs) per unit area (ft2) within the flaming front at the head of a fire. The ERC is very sensitive to fuel model characteristics - loading, compaction, particle size, heat of combustion and mineral content. The condition of the larger fuels has a greater influence on the ERC than the finer fuels. The scale for ERC values is open ended.

Burning Index (BI)

Burning Index relates the potential amount of effort needed to contain a single fire in a particular fuel type. Dividing Burning Index by 10 gives an approximate estimate of flame length in feet at the head of a fire. Burning Index is fuel model dependent.

1/10/100/1000-Hour Fuel Moisture

Dead fuel moisture content in fuel that takes the given number of hours to lose or gain 63% of the difference between the dead fuel itself and the surrounding atmosphere.