Defensible space (fire control)
Encyclopedia
In the context of fire control
, Defensible Space is the natural and landscaped area around a structure that has been maintained and designed to reduce fire danger, sometimes called 'Firescaping'. "Defensible space" is also used in the context of wildfire
s, especially in the wildland-urban interface
(WUI). This defensible space reduces the risk that fire will spread from the surroundings to the structure and provides firefighter
s access and a safer area to defend it from. Firefighters sometimes do not attempt protecting structures without adequate defensible space, for personnel safety and their effort less likely to succeed.
. This area need not be devoid of vegetation by using naturally fire resistive plants that are spaced, pruned and trimmed, and irrigated, to minimize the fuel mass available to ignite and also to hamper the spread of a fire.
An important component is ongoing maintenance of the fire-resistant landscaping for reduced fuel loads and fire fighting access. Fire resistive plants that are not maintained can desiccate
, die, or amass deadwood debris
, and become fire assistive. Irrigation systems and pruning can help maintain a plant's fire resistance. Maintaining access roads and driveways clear of side and low-hanging vegetation can allow large fire equipment to reach properties and structures. Some agencies recommend clearing combustible vegetation at minimum horizontal 10 feet from roads and driveways a vertical of 13 feet 6 inches above them. Considering the plant material involved is important to not create unintended consequences to habitat integrity and unnecessary aesthetic issues. Street signs, and homes clearly identified with the numerical address, assist access also.
and native habitat
loss can result from some unskillful defensible space applications. The disturbance of the soil surface, such as garden soil cultivation
in and firebreak
s beyond native landscape zones areas destroy the native plant cover and expose open soil, accelerating invasive species
of plants ('invasive exotics') spreading and replacing native habitat
s.
In suburban and wildland-urban interface
areas the vegetation clearance and brush removal ordinances of municipalities for defensible space can result in mistaken excessive clearcutting
of native and non-invasive introduced
shrubs and perennials that exposes the soil to more light and less competition for invasive plant species
, and also erosion and landslides. Negative aesthetic consequences to natural and landscape areas can be minimized with integrated and balanced defensible space practices.
Fire control
control of fire 'control of fire' is the practice of reducing the heat output of a fire, or reducing the area over which the fire exists, or suppressing or extinguishing the fire by depriving a fire of fuel, oxygen or heat ....
, Defensible Space is the natural and landscaped area around a structure that has been maintained and designed to reduce fire danger, sometimes called 'Firescaping'. "Defensible space" is also used in the context of wildfire
Wildfire
A wildfire is any uncontrolled fire in combustible vegetation that occurs in the countryside or a wilderness area. Other names such as brush fire, bushfire, forest fire, desert fire, grass fire, hill fire, squirrel fire, vegetation fire, veldfire, and wilkjjofire may be used to describe the same...
s, especially in the wildland-urban interface
Wildland-urban interface
A wildland–urban interface refers to the zone of transition between unoccupied land and human development. Communities that are within of the zone may also be included...
(WUI). This defensible space reduces the risk that fire will spread from the surroundings to the structure and provides firefighter
Firefighter
Firefighters are rescuers extensively trained primarily to put out hazardous fires that threaten civilian populations and property, to rescue people from car incidents, collapsed and burning buildings and other such situations...
s access and a safer area to defend it from. Firefighters sometimes do not attempt protecting structures without adequate defensible space, for personnel safety and their effort less likely to succeed.
Criteria
- A first concept of Defensible Space for most fire agencies' primary goal of fuel reduction is a recommended or required defensible space around a structure to extend for at least 100 feet (30.5 m) in all directions.
- A second concept of Defensible Space is "Fuel Reduction." This means plants are selectively thinned and pruned to reduce the combustible fuel mass of the remaining plants. The goal is to break up the more continuous and dense uninterrupted layer of vegetation.
- A third concept of Defensible Space is "Fuel LadderFuel ladderA fuel ladder is a firefighting term for live or dead vegetation that allows a fire to climb up from the landscape or forest floor into the tree canopy. Common fuel ladders include tall grasses, shrubs, and tree branches, both living and dead...
" management. Like rungs on a ladder, vegetation can be present at varying heights from groundcovers to trees. Grounds fuel 'rungs' such as dried grasses, can transmit fire to shrub rungs, which then transmit up tree branch rungs into the tree canopy. A burning tree produces embers that can blow to new areas spreading and so making it more difficult to control a wildland fire. One guideline is for a typical separation of three times the height of the lower fuel to the next fuel ladder. For example, a 2 foot (0.6096 m) shrub under a tree would need a spacing of 6 feet (1.8 m) to the lowest limbs of the tree. Since wildfires burn faster uphill than on flat land, fuel ladder spacing may need to be greater for slopes.
Landscape use
The term Defensible Space in landscape ('firescape') use refers to the 100 feet (30.5 m) zone surrounding a structure. Often the location is in the wildland-urban interfaceWildland-urban interface
A wildland–urban interface refers to the zone of transition between unoccupied land and human development. Communities that are within of the zone may also be included...
. This area need not be devoid of vegetation by using naturally fire resistive plants that are spaced, pruned and trimmed, and irrigated, to minimize the fuel mass available to ignite and also to hamper the spread of a fire.
- The first 30 feet (9.1 m) is the "Defensible Space Zone," of a defensible space around a structure. It is where vegetationVegetationVegetation is a general term for the plant life of a region; it refers to the ground cover provided by plants. It is a general term, without specific reference to particular taxa, life forms, structure, spatial extent, or any other specific botanical or geographic characteristics. It is broader...
is kept to a minimum combustible mass. A guideline used in this zone can be "low, lean and green." - The second distance of 30 to 100 ft (9.1 to 30.5 m), is the "Reduced Fuel Zone" of a defensible space around a structure. In this area of the defensible space, fuels/vegetation are separated vertically and horizontally depending on the vegetation type. This is done by: thinning, pruning, and removal of selected vegetation; and limbing up trees from lower vegetation and the lateral separation of tree canopiesCanopy (forest)In biology, the canopy is the aboveground portion of a plant community or crop, formed by plant crowns.For forests, canopy also refers to the upper layer or habitat zone, formed by mature tree crowns and including other biological organisms .Sometimes the term canopy is used to refer to the extent...
. types.
An important component is ongoing maintenance of the fire-resistant landscaping for reduced fuel loads and fire fighting access. Fire resistive plants that are not maintained can desiccate
Desiccation
Desiccation is the state of extreme dryness, or the process of extreme drying. A desiccant is a hygroscopic substance that induces or sustains such a state in its local vicinity in a moderately sealed container.-Science:...
, die, or amass deadwood debris
Coarse woody debris
Coarse woody debris is a term used in English-speaking countries for fallen dead trees and the remains of large branches on the ground in forests. Some prefer the term coarse woody habitat . A dead standing tree is known as a snag and provides many of the same functions as coarse woody debris...
, and become fire assistive. Irrigation systems and pruning can help maintain a plant's fire resistance. Maintaining access roads and driveways clear of side and low-hanging vegetation can allow large fire equipment to reach properties and structures. Some agencies recommend clearing combustible vegetation at minimum horizontal 10 feet from roads and driveways a vertical of 13 feet 6 inches above them. Considering the plant material involved is important to not create unintended consequences to habitat integrity and unnecessary aesthetic issues. Street signs, and homes clearly identified with the numerical address, assist access also.
- The slogan "Provide Defensible Space, be fire-safe and fire-smart" is used by agencies.
Unintended consequences
The unintended negative consequences of erosionErosion
Erosion is when materials are removed from the surface and changed into something else. It only works by hydraulic actions and transport of solids in the natural environment, and leads to the deposition of these materials elsewhere...
and native habitat
Habitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
loss can result from some unskillful defensible space applications. The disturbance of the soil surface, such as garden soil cultivation
Tillage
Tillage is the agricultural preparation of the soil by mechanical agitation of various types, such as digging, stirring, and overturning. Examples of human-powered tilling methods using hand tools include shovelling, picking, mattock work, hoeing, and raking...
in and firebreak
Firebreak
A firebreak is a gap in vegetation or other combustible material that acts as a barrier to slow or stop the progress of a bushfire or wildfire. A firebreak may occur naturally where there is a lack of vegetation or "fuel", such as a river, lake or canyon...
s beyond native landscape zones areas destroy the native plant cover and expose open soil, accelerating invasive species
Invasive species
"Invasive species", or invasive exotics, is a nomenclature term and categorization phrase used for flora and fauna, and for specific restoration-preservation processes in native habitats, with several definitions....
of plants ('invasive exotics') spreading and replacing native habitat
Habitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
s.
In suburban and wildland-urban interface
Wildland-urban interface
A wildland–urban interface refers to the zone of transition between unoccupied land and human development. Communities that are within of the zone may also be included...
areas the vegetation clearance and brush removal ordinances of municipalities for defensible space can result in mistaken excessive clearcutting
Clearcutting
Clearcutting, or clearfelling, is a controversial forestry/logging practice in which most or all trees in an area are uniformly cut down. Clearcutting, along with shelterwood and seed tree harvests, is used by foresters to create certain types of forest ecosystems and to promote select species that...
of native and non-invasive introduced
Introduced species
An introduced species — or neozoon, alien, exotic, non-indigenous, or non-native species, or simply an introduction, is a species living outside its indigenous or native distributional range, and has arrived in an ecosystem or plant community by human activity, either deliberate or accidental...
shrubs and perennials that exposes the soil to more light and less competition for invasive plant species
Invasive species
"Invasive species", or invasive exotics, is a nomenclature term and categorization phrase used for flora and fauna, and for specific restoration-preservation processes in native habitats, with several definitions....
, and also erosion and landslides. Negative aesthetic consequences to natural and landscape areas can be minimized with integrated and balanced defensible space practices.
See also
- Fire controlFire controlcontrol of fire 'control of fire' is the practice of reducing the heat output of a fire, or reducing the area over which the fire exists, or suppressing or extinguishing the fire by depriving a fire of fuel, oxygen or heat ....
- Fire ecologyFire ecologyFire ecology is concerned with the processes linking the natural incidence of fire in an ecosystem and the ecological effects of this fire. Many ecosystems, such as the North American prairie and chaparral ecosystems, and the South African savanna, have evolved with fire as a natural and necessary...
- Firefighting
- Fuel ladderFuel ladderA fuel ladder is a firefighting term for live or dead vegetation that allows a fire to climb up from the landscape or forest floor into the tree canopy. Common fuel ladders include tall grasses, shrubs, and tree branches, both living and dead...
- WildfireWildfireA wildfire is any uncontrolled fire in combustible vegetation that occurs in the countryside or a wilderness area. Other names such as brush fire, bushfire, forest fire, desert fire, grass fire, hill fire, squirrel fire, vegetation fire, veldfire, and wilkjjofire may be used to describe the same...
- Wildfire suppression
External links
- CAL-FIRE: Homepage + Links Official CA State Board of Forestry and Fire Protection website.
- CA State Board of Forestry and Fire Protection: "General Guidelines for Creating Defensible Space"
- SBCFD Homepage + Links: "Defending Your Home and Hazard Reduction" Official Santa Barbara County Fire Department 'Wildfire' Website.
- Santa Barbara County Fire Department: "Landscape Checklist"
- Santa Barbara County Fire Department: "Homeowner Checklist"