Fuels, Weather, and Fire Behavior

Fire Triangle

Fire behavior is controlled by three interacting components: fuels, weather, and topography. Fuels provide the energy source for fire. Fuel availability, which depends on both fuel arrangement and fuel moisture, determines if fires will burn as ground, surface, or crown fires. Weather elements, such as temperature, relative humidity, wind, precipitation, and atmospheric stability, also combine to influence fire behavior by regulating fuel moisture and rate of spread. Topography can influence fire indirectly, by mediating wind patterns, or directly- fires burning upslope spread faster than fire burning on flat land.

The variety of fuel, weather, and topographical conditions that exist in the South create fires that vary in the amount of fuels that burn, the rate at which these fuels burn, the depth of burns, and whether living plants become fuel. This variation in fire behavior, in turn, influences the effects of fire on natural communities and people. This section of the encyclopedia provides a background on how fuels, weather, and topography influence fire behavior.

• Fire, Weather, and Fire Behavior- Overview

• Fuels: This section defines fuel categories (ground, surface, ladder, and canopy fuels); explains how physical fuel properties, such as size, shape, loading, and arrangement, combine to influence combustion and fire behavior; explains how chemical fuel properties affect heat content and flammability; describes the importance of fuel moisture and other factors that control fuel availability.

• Fire Weather: This section defines important components of fire weather and explains how each of these components influence fire behavior and risk of wildfire.

• Fire Behavior: This section explains how fuels, weather, and topography combine to influence fire behavior. It includes a discussion of combustion and heat transfer, fire intensity, fire growth and spread, extreme fire behavior, and fire behavior prediction systems.