Living with Fire              Why We’re Worried              The Fire Environment    
Defensible Space              Making Your Home Defensible    
When Wildfire Approaches              Fire Department Phone Numbers

The fire environment is defined as the “surrounding
conditions, influences, and modifying forces that
determine wildfire behavior.” Firefighters recognize three components: weather, topography and fuel. These components affect the likelihood of a fire starting, the speed and direction at which a wildfire will travel, the intensity at which a wildfire burns and the ability to control and extinguish a wildfire. Although weather and topography cannot be changed, the fuels (or vegetation) can be modified. Consequently, many of our
opportunities to reduce the wildfire threat lie in proper
management and manipulation of wildland vegetation. 

Of topographic features, steepness of slope most influences fire behavior. As the steepness of slope increases, the fire spreads more quickly. Other important topographic features include aspect (south and southwest slopes usually have more fires) and steep, narrow drainages (chimneys), which can significantly increase the rate of firespread. 

Dry, hot and windy weather increases the likelihood of a major wildfire. These conditions make ignition easier, allow fuels to burn more rapidly and increase fire intensity. High wind speeds, in particular, can transform a small, easily controllable fire into a catastrophic event in a matter of minutes. 

Fuel is required for any fire to burn. In regard to wildfire, fuels almost always consist of living vegetation (trees, shrubs, grass, and wildflowers) and dead plant material (dead trees, dried grass, fallen branches, pine needles, etc.) Houses, when involved in a wildfire, become a source of fuel. The amount, size, moisture content, arrangement and other fuel characteristics influence ease of ignition, rate of fire spread, length of flames produced and other fire behaviors. 

When people are living in high-hazard fire environments, the human-built environment becomes an important factor in predicting the loss of life and property. Wood shake and shingle roofs, narrow roads, limited access, lack of fire-wise landscaping, inadequate water supplies and poorly planned subdivisions increase the risks to people living with the threat of wildfire. Humans also start wildfires.