Prevention & Mitigation

Req 4b — WUI & Defensible Space

4b.

Wildfire Prevention and Mitigation. Discuss Wildfire Mitigation:.

Mitigation refers to taking proactive actions before a fire occurs to reduce the severity of wildfire damage to structures and natural resources.

Requirement 4b1: The Wildland-Urban Interface (WUI)

4b1.

Wildland-Urban Interface

The Wildland-Urban Interface (WUI) (pronounced “WOO-ee”) is any area where human homes, buildings, and infrastructure meet or intermingle with undeveloped wildland vegetation and flammable fuels.

Why the WUI Present Special Wildfire Challenges

  • Dual Exposure: Structures in the WUI are vulnerable both to direct wildfire flame fronts and to wind-blown embers traveling over a mile ahead of the main fire.
  • Evacuation Bottlenecks: Narrow mountain or rural roads can become clogged with fleeing residents, blocking incoming fire engines.
  • Resource Division: Firefighters must divide limited crews between fighting the wildland fire front and performing structural defense on individual homes.

Requirement 4b1 Resources

Understanding the Wildland Urban Interface Interactive ArcGIS StoryMap exploring WUI growth trends, maps, and community wildfire risks. Link: Understanding the Wildland Urban Interface — https://storymaps.arcgis.com/stories/6b2050a0ded0498c863ce30d73460c9e

Requirement 4b2: Defensible Space and Home Hardening

4b2.

Defensible space and how homes and communities in the wildland-urban interface can be protected from wildfire

Defensible space is a buffer area created around a building by clearing or thinning flammable vegetation to reduce fire intensity and give firefighters a safe zone to defend the structure.

Labeled diagram showing Zone 0 (0-5ft), Zone 1 (5-30ft), and Zone 2 (30-100ft) around a residential home

The Three Zones of Defensible Space

[ Structure ] → Zone 0 (0-5 ft) Non-combustible → Zone 1 (5-30 ft) Clean & Lean → Zone 2 (30-100 ft) Reduced Fuel
  1. Zone 0 — Immediate Ember-Resistant Zone (0 to 5 feet):
    • Use non-combustible landscaping (gravel, concrete, stone).
    • Keep gutters, roofs, and decks completely free of dead leaves and pine needles.
    • Install 1/8-inch metal mesh over attic and crawlspace vents to block flying embers.
  2. Zone 1 — Lean, Clean, and Green Zone (5 to 30 feet):
    • Remove all dead plants, grass, and weeds.
    • Space trees so canopies maintain at least 10 feet of separation.
    • Prune tree branches up to 6–10 feet off the ground to eliminate fuel ladders.
  3. Zone 2 — Reduced Fuel Zone (30 to 100+ feet):
    • Cut annual grass down to a maximum height of 4 inches.
    • Remove dense underbrush and create horizontal spacing between tree clusters.

Requirement 4b2 Resources

🎬 Video: Separating Your Home From Wildfire—the Zones of Defensible Space — https://youtu.be/isf6COwOXPw

Separating Your Home From Wildfire—the Zones of Defensible Space

Next Steps

Now that you understand prevention and defensible space, examine the physics of fire behavior and the fire triangle.