According to a publication by the Washington State
Department of Natural Resources, "Living with Fire, A Guide for the
Homeowner,"
"Defensible
space is the area between a house and an oncoming wildfire where the vegetation
has been modified to reduce the wildfire threat and to provide an opportunity
for firefighters to effectively defend the house. Sometimes, a defensible space
is simply a homeowner's properly maintained backyard."
When evaluating the risk of wildfire, firefighting professionals look at three components:
1. Weather- Hot temperatures can lead to
dry plants easily catching fire and wind can spread the fire quickly over a
large area.
2. Topography- Steep slopes spreads fires
more quickly than flat land.
3. Fuel- In the case of wildfires, fuel is
living vegetation (trees, shrubs, grass, wildflowers) and dead plant material
(dead trees, dried grass, fallen branches, pine needles, etc.). Houses can also
add fuel with the materials such as untreated wood shakes and shingles.
The component that can be controlled the easiest is the fuel
around the house.
The aim of defensible space is to change the vegetation
around the home by:
•
Increasing the moisture content of plants.
•
Decreasing the amount of flammable vegetation.
•
Shortening plant height.
• Altering
the arrangement of plants.
In order to do this, firefighting professionals rely on the
three R's:
1. Removal- Taking away trees and shrubs
that are dead or are most volatile in a fire such as junipers.
2. Reduction- Removing dead wood from
trees and shrubs, low tree branches, and mowing dead grass.
3. Replacement- Replacing flammable plants
for plants that are not as flammable.
30 foot and 100 foot
zones. Create two zones where you clear flammable material.
Zone 1- This zone is 30 feet from your house. In it you only
have small amounts of flammable vegetation, no dead vegetation or flammable
debris such as twigs, branches, dried grass.
Plants in this zone are well maintained and irrigated. Also, be sure
that your roof does not have dry debris such as needles or branches. Any tree
branches near your house should be at least 10 feet away from your chimney.
Zone 2- This zone is between 30 and 100 feet from your
house. Where you can thin trees so that they are at least 10 feet apart on flat
land. Between a 20-40% slope, trees should be 20 feet apart. If there is a 40% or steeper slope, thin
trees to at least 30 feet apart. Shrubs should be spaced double the size of the
shrub on flat land, 4 times the size on 20-40% slopes and 6 times the size on 40% or greater
slopes. For example, on flat land if shrubbery is 6 feet in diameter, keep them
12 feet apart.
Ladder effect.
Fire tends to climb like up a ladder. So if shrubs that are next to trees catch
fire, the fire will jump to the trees.
Firefighters recommend that there be a vertical separation of three
times the height of shrubs to the lower branches of adjacent trees. For example, if shrubbery next to trees is 3
feet tall, prune away the branches of the trees to 9 feet high.
Comment: Raising concerns about wildfire danger is highly
unusual. Normally, we have wet Junes until July 4. Summer weather starts on
July 5 and only lasts until the end of September. But, last year we saw a dry
June, followed by a hot and dry June this year. Long range forecasts apparently
say that this summer will continue to be hot and dry. At least one local fire
official has said that forecasts predict another hot and dry summer for 2016
with relief taking as long a 2017 to arrive.
Our forest land on the west slopes of the Cascades have
traditionally been moist enough to allow for lush forests and undergrowth. With
this long term dry spell, homeowners and communities need to assess whether or
not they need to re-adjust their landscaping to protect their homes. Some
communities may have little that they can or need to do. Others may need to
clean away flammable material to ensure that buildings are protected. If you
have any questions about fire safety around your home, contact your local fire
district.
Department of Natural Resources:
KING TV:
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