understanding urban fire zones
Home Ignition Zone
For Managing Individual Properties
Immediate Zone
0-5 Feet
Hardening your home is the most important thing you can do to protect it from wildland/urban fire. This is a five foot noncombustible bubble around, above, and even below your home! Things to look out for include: modern roof, covered gutters, double pane windows, no firewood on your deck, etc. For (sub)urban homeowners who don't have defensible space, home hardening will be your top priority.
Intermediate Zone
5-30 Feet
This is your lawn and garden space. In this zone, you still want to avoid highly flammable plants or mulches that could have a tall flame within reach of your home. If you have excitable plants like junipers, just keep them in the outer edges of this zone. Keep this area trimmed up and free of unnecessary hazards like wood piles, trash cans, stacked construction materials, or vehicles/boats.
*Unlike these images, keep potted plants away from the sides of your home.
Extended Zone
30-100 Feet
Few homeowners in western states have a home on a half acre lot - the size you need to ensure the perfect amount of defensible space (assuming you're right square in the middle of the lot with equal spacing all the way around).
On your average one acre lot, or city block, you have 4-10 homes. In high density urban areas, it can be 20 homes. That doesn't give you the space you need to protect you from anything, let alone jumping flames and radiant heat.
Ember Zone/Community Ignition Zone
For Mitigating Multiple Properties (Residential and Commercial)
Wildland Urban Intermix
1-250
Technically defined as 1-250 structures (cars, homes, sheds) per square mile, which equates to 1 home , these homes now have the advantage. It is much easier to remove some plants than it is to remove some neighboring houses....
Homes in this zone can harden their homes and have adequate defensible space, allowing them a significantly higher chance of survival. Less cooperation is needed between neighbors.
Wildland Urban Interface
30-250
60,000+ communities and approximately 115 Million Americans live in the wildland urban interface.
Technically defined as 30-250 structures per square mile, and/or communities within 1.5 miles of wildlands, it was incorrectly assumed to only apply to rural forest communities for many decades. We are now realizing that more communities are risk than we ever thought possible. Cooperation between neighbors, and community stakeholders, is essential.
High Density Urban Areas
250-5000
Though still part of the Wildland Urban Interface, high density urban areas were always considered safe from wildfire because they were "in town" and not part of the "wild" or "rural" areas.
Early fuel and fire behavior models always showed fires magically stopping at the urban boundaries, leading us to this false sense of security, when the reality is, in extreme fire events, houses are still fuel, response teams get overwhelmed, and these areas become our most dangerous infernos.
Know Your Fire Prone Ecosystem & Fire Return Interval
The following is a work in progress and provided as an estimate for you to understand what your historic ecosystem and fire return intervals were. In our blog we'll go into detail on how they may have been affected by the introduction of cattle grazing, settlement, and invasive plant species, and how this may alter historic predictive models.
Arizona
3
Mogollan Rim (Ponderosa Pine Savannah)
5-20yr fire return interval
Flagstaff, Payson, Show Low, Prescott
Sonoran Desert (Lowland Scrub Desert)
100-1000+yr fire return interval
Phoenix, Tuscon, Casa Grande, Marana
increasing fire return with invasive species like cheatgrass, buffelgrass, and saltcedar.
Sky Islands (High Elevation Forests)
10-50yr fire return interval
Mt. Lemmon, Chiricahua Mountains, Coronado National Forest area
Northern California
5
Coastal Range 30-90yrs
Crescent City, Fort Bragg, SF
Cascades & Klamath
7-15 yrs (mixed conifer)
10-140 (doug fir mixed)
80-275 (spruce-hemlcok)
Yreka, Redding, Chico
Eastern Cascades 10-40yrs
Modoc Plateau, Mammoth, Alturas
Sierra Nevada 5-20yrs
Lake Tahoe
Central Coastal Mountains & Central Foothills
10-120yrs (coastal redwoods)
10-60yrs (chaparral
Napa, San Jose Bay Area, Monterey
Central California
3
Central Valley 30-90yrs
Sacramento, San Joaquin Valley, Fresno, Bakersfield
Central Basin 20-80yrs
Bridgeport, Bishop
Northern Basin 20-130yrs
Ft Bidwell, Menlo Baths
Southern California
4
SoCal Mountains
30-130yrs
Ojai, Santa Clarita, Big Bear, Palm Desert
Baja Coast
15-30 yrs (chaparral)
20-90yrs (chamise-redshank)
LA, Santa Ana, San Diego
Mojave Basin
30-130yrs
Death Valley, Ridgecrest, Victorville, Vidal
Sonoran Basin
500-1000yrs
Blythe, Ocotillo, Salton Sea
Colorado
6
Wyoming Basin
7-20 yrs (prairie & ponderosa pine)
20-50yrs (upper montana)
300+ yrs (spruce-fir)
60-125yrs sagebrush steppe
100-300+ wyoming-big sagebrush
Colorado Plateau
300-600+ yrs (pinyon-juniper)
8-25yrs (mixed conifer)
Southern Rockies
100-300yrs: subalpine forest
7-25yrs: prairie-ponderosa
20-30yrs: ponderosa-doug fir
Arizona/New Mexico Plateau & Southwestern Tablelands
7-25yrs: prairie-ponderosa
60-300yrs: sagebrush
300-600+: pinyon-juniper
Great Plains 1-35yrs
Florida
4
Longleaf Pine 2-5yrs
Flatwoods 1-10yrs
Sandhill-Prairie 1-5yrs
Everglades 1-300yrs
Northern Idaho
6
Columbia Plateau ()
x
Blue Mountains ()
x
Snake River Plains ()
x
Northern Rockies ()
x
Idaho Batholith ()
x
Middle Rockies ()
x
Northern Basin ()
x
Southern Idaho
6
Columbia Plateau ()
x
Blue Mountains ()
x
Snake River Plains ()
x
Northern Rockies ()
x
Idaho Batholith ()
x
Middle Rockies ()
x
Northern Basin ()
x
Montana
4
Northern/Canadian Rockies ()
x
Eureka, Whitefish, Kalispell, Missoula
Idaho Batholith ()
x
Middle Rockies ()
x
Glaciated & Great Plains ()
Billings, Great Falls, Cut Bank, Plentywood, Glendive, Colstrip
New Jersey
5
Ridge & Valley ()
x
Northeastern Highlands ()
x
Northern Piedmont ()
x
Altantic Coastal Pine Barrens ()
x
Middle Atlantic Coastal Plains ()
x
New Mexico
7
Colorado Plateau ()
x
Southern Rockies ()
x
AZ/NM Plateau ()
x
AZ/NM Mountains ()
x
Chihuahuan Desert ()
x
High Plains ()
x
Southwestern Tablelands ()
x
Oklahoma
8
High Plains
Southwestern Tablelands
South Central Plains
Ouachita Mountains
Arkansas Valley
Boston Mountains
Ozark Highlands
Central Irregular Plains
Oregon
7
Coast Range
Willamette Valley
Cascades & Klamath Mountains
Eastern Cascades
Columbia Plateau
Blue Mountains
Northern Basin Range
North/West Texas
6
Chihuahua Desert
High Plains
Southwestern Tablelands
Central Great Plains
Cross Timbers
Edwards Plateau
South/East Texas
5
Southern Texas Plains
Laredo, Hondo
Blackland Prairies
Dallas, Austin, San Antonio
East Central Texas Plains
Western Gulf Coastal Plains
Houston, Corpus Christie
Southern Central Plains
Utah
3
Central Basin Range
Wasatch & Uinta Mountains
Colorado Plateau
Washington
7
Coastal Range
Puget Sound
Cascades & Eastern Cascades
Columbia Plateau
Northern Rockies
Northern Cascades
Wyoming
5
Middle Rockies
Southern Rockies
Wyoming Basin
High Plains
Northwestern Great Plains
x