Towns and cities are
spreading into the surrounding countryside as more and more people
move out to the woods. If you live on forested property, or are
considering building there, you are part of the growing wildland-urban
interface – where the urban environment meets the wild.
In 2007, nearly every fire in the West involved
structures, and many of those structures were homes on the wildland/urban
interface. The season starts early in the west, with spring
wildfires being common in New Mexico and Arizona until early July,
when they can expect the summer monsoon season to begin. As the
temperatures rise and the precipitation rates drop, the rest of the
west begins to dry out. Fire season in Idaho usually gets going
about the second week of July and can last well into October in the
lower elevations. Statistics for the 2007 fire year report over
85,000 wildland fires with more than 9.3 million acres burned -
that’s almost 14,000 square miles, an area four times the size of
Yellowstone National Park. An estimated 5,200 building were
destroyed, ranking second to the 2003 fire season, when 5,700
buildings were lost.
Things were seen last year that had never been seen
before. Things happened that were not supposed to happen. Any many
feel that last year’s fire season was not abnormal, but the new
normal. It may be muddy outside right now, or you may even still
have snow on the ground, but if you live in the Inland West it is
never too soon to think about the next fire season. Residents of the
forested areas of Idaho should view wildfire the same way residents
of the Midwest view tornadoes – an expected natural phenomenon that
can devastate property and life – and prepare accordingly.
The Home Ignition Zone.
The
most effective ways to increase the protection of your home from
wildfire is to reduce the ignition potential of your home and
surrounding landscape.
Home
ignition zones are those areas of your home and outbuildings that
are the most susceptible to ignition. There are three sources of
ignition. Heat can be moved from one piece
of fuel to another by conduction. Larger fuels must usually
be in contact with, or close to each other for conduction to
transfer enough heat for kindling to occur. A home with a well
defined and well maintained defensible space will be nicely
protected from surface fires that are moving via conduction.
A second type of ignition occurs when radiation
contributes to the fire spread by preheating and drying small fuels
to their ignition points. Radiation can occur with both surface and
crown fires, and can ignite structures from up to 100 feet if
conditions are extreme.
A third phenomenon, convection,
preheats surface and vertical fuels, and contributes greatly to fire
spread by transporting embers which can ignite spot fires ahead of
the main burn. Most homes ignite by convection from burning
brands and embers that fall onto the roof of a house, a deck, or an
outbuilding. New research has shown that in many fires this is the
number one source of home ignitions.
Your Home.
In Figure 1 you will see
three zones. Zone 1 includes your home. Steps have been taken to
decrease and/or eliminate the ignition potential of your home.
Particular attention is paid to nonflammable roofing materials,
enclosing decks, soffits and overhangs, and removing debris from
roofs and gutters.
Figure 1. Home Ignition
Zones.
Zone 1.
Zone 2.
Zone 3.
If
you have not built yet, try to place structures on flat ground.
Fires burn uphill more rapidly than down or across a flat. Avoid
draws, as they can serve as a chimney, creating more intense fires
that spread rapidly with uphill drafts.
Use fire resistant
materials to build or to replace flammable materials. Tile, metal or
asphalt roofing materials and brick or stucco walls are the most
fire resistant. Untreated or poorly treated wood shake shingles are
the least fire resistant and in many cases, offer almost certain
ignition of your home.
Enclose the undersides of
decks and porches, eaves, soffits, and fascia with a nonflammable
material - cement products work well. Screens should be constructed
from noncombustible materials and vents should be screened to
prevent firebrands or other flammable objects larger than ¼” from
entering the space. Vents should also be boxed in with
noncombustible materials to reduce their size. PVC and vinyl
products should be avoided as they melt or burn at low temperatures.
Double pane windows and
protective shutters or fire-resistant window treatments (blinds,
drapes) will help insulate the inside of your house from the heat of
a fire, lessening the chance of the interior becoming overheated and
igniting.
Make sure your chimneys
are screened and construct covers for all attic and basement
openings. Pay attention to places where combustible materials meet
each other – a vine covered wooden fence leading up to your wooden
stairs can act like a trail of gunpowder leading to a barrel of
explosives. Also remove shrubs and combustible fencing from around
propane tanks and woodpiles. Park boats, campers, and other
flammable recreational vehicles in an enclosed area or away from
your home.
If possible, have power
lines buried to protect them from fire and prevent them from
igniting vegetation. If burying the lines is not possible contact
your power company to make sure trees and branches are trimmed 10 to
15 feet away from lines.
Your Landscape.
In Zone 2, approximately 100
feet around the home is surrounded by a
greenbelt of well-watered
and maintained plant materials. Perennials, groundcovers, and
annuals are planted in groupings with individual trees and shrubs.
These islands of vegetation are surrounded by rock or brick
retaining walls and well-watered turf. This zone requires removing
undergrowth and dry debris on the ground every three to five years
and pruning trees. Firewood is stored on a gravel pad and is also
surrounded by well-watered turf.
To prepare and maintain zone 2:
•
Remove highly flammable brush from around each home for at least 100
feet.
•
Remove shrubs at the base of structures.
•
Keep tree branches at least 15 feet away from chimneys and
stovepipes, utility lines and roofs.
•
Store firewood 30 to 100 feet from any structure and create a
defensible space around the pile.
•
Remove dead shrubs and trees.
•
Thin shrubs growing 100 feet and further from each house into
individual plants or remove them entirely.
•
Eliminate “ladder fuel” configurations in vegetation (ladder fuel
refers to the plant growth structured like the rungs of a ladder –
leaves, grasses, small shrubs, large shrubs, and trees). Removing
these “rungs” helps prevent destructive crown fires.
•
Reduce the chance of surface fire climbing into tree crowns by
pruning the base of the crown 6 to 15 feet from the ground.
•
Reduce lateral movement of fire between crowns by cutting branches
that span between crowns to 10 feet, or more, apart.
•
Prune all dead branches.
Beyond 100 feet.
Zone 3 (beyond 100 feet) is
composed of native plants that are thinned. If possible, highly
flammable vegetation is removed and replaced with less fire-prone
species. However, you do not have to be as aggressive in reducing
f
uels in these areas as you would immediately next to your house.
Leaving green branches or lopping them into small pieces will help
recycle nutrients to your trees. Coarse woody debris (wood larger
than 3 inches in diameter), has relatively low fire risk – leaving a
small amount of it, laying flat on the ground benefits forest growth
and wildlife. To avoid bark beetle problems, avoid cutting pines
larger than 3 inches in diameter in the winter and spring (or
destroy or peel the bark of stemwood pieces that size). For areas
with steep slopes or windswept exposures greater defense distances
will be needed.
Life in the wildland/urban
interface is enjoyable, but not without danger. In western forest
environments, wildfire should be anticipated and planned for, not
unexpected and dismissed. You have a choice – if you take
precautions to protect your property it will increase your chances
of escaping serious damage from wildfire.
For additional
information and informative figures and photos, email the
UI Extension Forestry office
and request a copy of Protecting and Landscaping Homes on the
Wildland Urban Interface. by Yvonne C. Barkley, Chris
Schnepf, and Jack Cohen. Station Bulletin No. 67, January, 2005.
Idaho Forest, Wildlife and Range Experiment Station, Moscow, ID.
