Firewise Landscaping

 
 Fireby Mark Brehl, Wildland Firewise Specialist
Flagstaff Fire Department
 
 
 
Wildfires sweep through northern Arizona’s forests, most often in May and June. Use the following information to reduce your home’s vulnerability to fire.
 
The basic exposures leading to structure ignition include:
  • direct flame impact
  • radiant heat
  • burning embers

The first two can be addressed by creating appropriate defensible space. Studies and post-fire analyses illustrate that defensible space of 30 feet is sufficient to limit ignition potential—the short heat pulse produced during a wildfire.

Ember exposure is the main fire vector leading to well over half of all structure losses during wildfires. Embers are lofted high into the air and can travel several miles before dropping to the ground. Ignition can occur if receptive fuel beds are present.

Ensure the area within 30 feet directly adjacent to structures is “clean and green,” without continuous fuel leading to the home. In our area, ponderosa pines drop about one-third of their needles in the fall; be sure to clear these from roofs and gutters and rake them away from your house.

Defensible space has many attributes including:

  • ignition resistant construction materials
  • non-combustible roof
  • paved walkways or gravel surrounding the home
  • screened vents
  • low flammability landscape plant selection
  • well-thinned surrounding forest.

To learn about landscaping with Firewise Plant Materials, see this helpful pdf: Firewise Plant Materials

References
Babrauskas, Vytenis. 2003. Ignition Handbook. Fire Science Publishers, Issaquah, WA. 111g pp.
Cohen, Jack D. 2004. Relating Flame Radiation to Home Ignition Using Modeling and Experimental Crown Fires. Canadian Journal of Forest Resources 34:1616-1626.
Manzello, Samuel L., John R. Shields, Thomas G. Cleary, Alexander Maranghides,
William E. Mell, Jiann C. Yang, Yoshihiko Hayashi, Daisaku Nii, and Tsuyoshi Kurita.2008.
On the development and characterization of a firebrand generator. Fire Safety Journal 43: 258–268
Manzello, Samuel L., Seul-HyunPark, SayakaSuzuki, JohnR.Shields, YoshihikoHayashi. 2011.
Experimental investigation of structure vulnerabilities to firebrand showers. Fire Safety Journal 46: 568–578.

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