Unit 2 Principles of Wildland Fire Behavior

South West

South East

All Materials on or immediately above

the ground including:

• needles
• leaves
• grass
• downed logs
• stumps
• large limbs
• low shrubs

• Moisture content determines how a easily a fuel will ignite and burn.
• Before a wet fuel can burn, moisture it contains mus evaporate.
• Different fuels in the same area will have various moisture levels.
• Similar type of fuels, across a broad area, will have different moisture levels.

Wet Fuels:

• Fuels that have a high moisture content because of exposure to precipitation or high relative humidity.

Dry Fuels:

• duels that have low moisture content because of prolonged exposure to sunshine, dry winds, drought, or low relative humidity.

All green and dead materials located

in the upper forest canopy including:

• tree branches
• crowns
• snags
• moss
• high shrubs

Solution

Fuel Loading

Fuel Moisture:

• Quantity of fuels in area
• Expressed in Tons/Acre

• Fuel availability for combustion

Fuel moisture content is the amount of the water contained with in the fuel.

• The fuel moisture content is expressed in percentages

Aerial Fuels

Fuel Arrangement:

Surface Fuels

Any Fuels that provide a connection

between the surface and upper canopy.

Ladder

The manner in which fuels are spread over a certain area.

All combustible materials lying beneath

the surface including:

• Deep Duff
• Roots
• Rotten buried logs
• Peat
• Any other organic material

Ground Fuels

Horizontal Continuity

• Affects rate of spread.

Horizontal Arrangement

Vertical Arrangement

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North East

North West

Fuel for thought

South West

Uniform Fuels

• Includes all fuels distributed continuously over the area

Surface-Area-to-Volume Ratio:

North East

Fuel Size Classes and Shape

South East

Patchy Fuels

• Includes all fuels distributed unevenly over the area, or areas of fuel with definite breaks or barriers present

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South West

Fuels with high surface area to the volume rations (i.e fine fuels). Can fluctuate with the RH (Relative Humidity) and precipitation in the local environment.

WHY DO I NEED TO KNOW THIS?

• Fuel moisture will change rapidly

• Fuels will ignite and burn out quickly

• Physical characteristics of fuels
• Divided into four categories on the basis of their size

• 10-hr fuels: 1/4 - 1 inch in diameter

6"

1'

6"

• 1-hour fuels: 0-1/4 inch in diameter

6"

SA: (1'*1')*6' = 6'

1'

SA: (6"*6")*6 = 216" per block

216"*8 = 1728" or 144'

• 100-hour fuels: 1 - 3 inches in diameter

1'

V=W*H*L

SA= W*H*6

• 1000-hour fuels: 3 - 8 inches in diameter

SA/V= Ratio

Fuel and Fuel Characteristics

Fuel Type

Fuel Loading

Fuel Availability

Fuels

Fuel Type

Grass/Shrubs

North West

North East

South West

South East

Grass

North West

North East

South West

Timber-Understory

North West

South East

North East

South West

South East

Exercise 1

For assigned fuel type:

1. list examples , near your area, where this fuel type occurs.

2. Explain why is this fuel type a possible concern to firefighters.

Defined anything that can be ignited and consumed.

• Live or dead plant material
• Man made products I.E urban settings with wildland interface

Shrub

North West

North East

South West

Slash - Blow down

North West

South East

North East

South West

South East

Timber Litter

North West

North East

Objectives

1. Identify the basic fuel types.

2. Identify the fuel characteristics that influence the the fire behavior.

Unit 2 B Fuels