Creating Defensible Space

Within the site, evaluate the defensible space by answering the following four questions:

1. Are there dead fuels present? Dead fuels include dead trees and shrubs, dead branches lying on the ground or still attached to plant, cured (yellowed and dried) grasses and forbs, leaves, and brown needles. Of particular concern are dead fuels that are less than one inch in diameter, such as pine needles, oak leaves, grass, twigs, and branches. In general, if dead fuels are present, they should be removed from the defensible space area.
2. Is there a continuous horizontal layer of vegetation present? Horizontal continuity of vegetation refers to areas where plants provide an uninterrupted, uniform layer of fuels, as opposed to growing in patches or widely spaced individual plants. The more continuous the fuel layer, the more rapidly a fire will spread, the greater potential for crown fire in timber types, and the greater the fire intensity. If the vegetation growing within the defensible space area provides a continuous horizontal layer, the goal of the homeowner should be to break up the continuity through the removal of plants.
3. Are there ladder fuels present? Fuels are often present at varying heights, similar to the rungs of a ladder. Under these conditions, flames from fuels burning at ground leve, such as pine needles, can be carried into taller fuels, such as shrub, which can ignite still taller fuels, such as tree branches. Vegetation that allows the fire to move from lower fuels into higher fuel layers is referred to as ladder fuel.
   Example of Ladder Fuel
   The ladder fuel problem can be addressed by raising the height of the upper fuel layer (removing the lower tree branches) or reducing the height of the lower fuel layer (mowing grasses, removing tall chaparral, orsmall trees). Withing the defensible space area, a vertical separation between fuel layers of at least three times the height of the lower fuel layer is recommended.
   
   Use the following guidelines in removing ladder fuels:
   Removal of lower branches should not exceed one third of the tree’s height.
   Lower branches should be removed up to at least six to eight feet in height when no understory vegetation is present.
   Lower branches from shrubs should be removed, providing at least 12 inches of separation from the ground.
   
   Does the height of surface fuels (grasses, shrubs and flowers) exceed 18 inches? The height of surface fuels influences fire behavior. Generally, as the height of the fuel increases so does the flame length. Shorter flame lengths improve the survivability of the house during a wildfire and increases the chance the fire can be controlled by firefighters.
   
   Reducing the height of shrubs can be performed by pruning. The height of re-sprouting shrubs can also be effectively reduced by cutting the main trunk near the ground. On a regular basis thereafter, maintain the height of the re-sprouting shrub at 18 inches through regular pruning.

STEP THREE – DEVELOP A DEFENSIBLE SPACE PLAN

This plan should list what tasks are needed to create your defensible space.

STEP FOUR – CONTACT A REGISTERED PROFESSIONAL FORESTER IF NECESSARY

If merchantable trees are planned for commercial removal, contact CDF to determine if the forest practice rules apply, then contract with a Registered Professional Forester for the preparation of a Timber Harvest Plan. Good forest silviculture practices will insure a future healthy forest ecosystem.