Difference between revisions of "Wildfire suppression"

Revision as of 14:07, 15 September 2010 (view source) Citation bot (Talk) m (Citations: [186] added: isbn, postscript. Tweaked: url, pages, volume, journal, doi. Unified citation types. User-activated.)	Latest revision as of 20:36, 20 September 2010 (view source) Jontas (Talk | contribs) m (1 revision)
(No difference)

---

Latest revision as of 20:36, 20 September 2010

Part of a series on Wildland Firefighting
140px
Main articles
Wildfire  · Bushfire Wildfire suppression
Agencies
National Interagency Fire Center USFS  · BLM CALFIRE  · CALFIRE Aviation New South Wales Rural Fire Service  · Country Fire Authority, Victoria  · Country Fire Service, South Australia
Tactics & Equipment
Incident Command System Aerial firefighting Controlled burn Firebreak  · Fire trail Fire lookout tower Fire-retardant gel Fire fighting foam Fire retardant  · MAFFS Helicopter bucket  · Driptorch
Personnel
Handcrew  · Hotshots Helitack  · Smokejumper Rappeller  · Engine crew
Lists
List of wildfires Glossary of wildfire terms This box: view talk edit

Wildfire suppression refers to the firefighting tactics used to suppress wildfires. Firefighting efforts in wildland areas requires different techniques, equipment, and training from the more familiar structure fire fighting found in populated areas. Working in conjunction with specially designed firefighting aircraft, these wildfire-trained crews suppress flames, construct firelines, and extinguish flames and areas of heat to protect resources and natural wilderness. Wildfire suppression also addresses the issues of the wildland-urban interface, where populated areas border with wildland areas.

History

United States

Wildfire suppression in the United States has had a long and varied history. For most of the 20th century, any form of wildland fire, whether it was naturally caused or otherwise, was quickly suppressed for fear of uncontrollable and destructive conflagrations such as the Peshtigo Fire in 1871 and the Great Fire of 1910. In the 1960s, policies governing wildfire suppression changed due to ecological studies that recognized fire as a natural process necessary for new growth. Today, policies advocating complete fire suppression have been exchanged for those who encourage wildland fire use, or the allowing of fire to act as a tool, such as the case with controlled burns.

Canada

Canada has about 4,020,000 km² of forest land, of which the Boreal forest—characterized by its predominance of coniferous trees—makes up nearly three-quarters. More than ninety percent of forest land is publicly owned, and the provincial and territorial governments are responsible for fire-suppression activities. The Federal Canadian Interagency Forest Fire Centre (CIFFC) provides operational fire-control services and links to all provincial and territorial fire agencies.

During a typical year there are over 9,000 forest fires in Canada, burning an average of 2.5 million hectares (ha) or 25,000 square kilometres. The number of fires and area burned can vary dramatically from year to year. Average suppression costs are $300 million to $500 million annually.

In Canada, two-thirds of all forest fires are caused by people, while lightning causes the remaining third. Despite this, lightning fires account for over 85% of the area burned in Canada, largely because many of the lightning-caused fires occur in remote, inaccessible areas. Currently about ninety percent of forest fires are fought. Generally fires near communities, industrial infrastructure, and forests with high commercial and recreation value are given high priority for suppression efforts. In remote areas and wilderness parks, fires may be left to burn as part of the natural ecological cycle.^[1]

Australia

Wildland fire, known in Australia as bushfire, has played a major role in Australia due to arid conditions similar to those in the western U.S. Notable fire services tasked with wildfire suppression include the New South Wales Rural Fire Service, the South Australian Country Fire Service, and the Victorian Department of Sustainability and Environment and the volunteer Country Fire Authority.

Objectives

Safety

Protection of human life, both firefighters and civilians, is first priority. When arriving on a scene a fire crew will establish a safety zone(s), escape routes, verify communication is in place and designate lookouts (known in the U.S. by the acronym LCES, for lookouts, communications, escape routes, safety zones). This allows the firefighters to engage a fire with options for a retreat should their current situation become unsafe. Although other safety zones should be designated, areas already burned generally provide a safe refuge from fire provided they have cooled sufficiently, are accessible, and have burned enough fuels so as to not reignite. Briefings may be done to inform new fire resources of hazards and other pertinent information.^[2]

A great emphasis is placed on safety and preventing entrapment, or a situation where escape from the fire is impossible. Prevention of this situation is reinforced with a list of 10 fire orders and 18 watch out situations for firefighters to be aware of, which warn of potentially dangerous situations. As a last resort, many wildland firefighters carry a fire shelter. In this unescapable situation, the shelter will provide limited protection from radiant and convective heat, as well as superheated air. Entrapment within a fire shelter is called a burnover. In Australia, firefighters rarely carry fireshelters, (commonly referred to as "Shake 'N' Bake" shelters) rather training is given to locate natural shelters or the use of handtools to create protection. Or in the instance of 'burnover' in a Tanker or other fire appliance, 'fire over-run' training is used.^[3]

Hazards beyond the fire are posed as well. A very small sample of these include: unstable hazard trees, animals, electrical cables, unexploded ordnance, hazardous materials, rolling and falling debris, and lightning.^[2]

Resource protection

Other resources are ranked according to importance and/or value. These include but are not limited to human health and safety, construction cost, ecological impacts, social and legal consequences and the costs of protection. Defendability is also considered, as more effort will be expended on saving a house with a tile roof than one with a wooden-shake roof, for example.^[4][5]

Management

Managing any number of resources over varying-size areas in often very rugged terrain is extremely challenging. An incident commander (IC) is charged with overall command of an incident. In the U.S., the Incident Command System designates this as being the first on scene providing he has sufficient training. The size of the fire, measured in acres or chains, will later dictate the class-level of IC required. Incident management teams aid on larger fire incidents to meet more complex priorities and objectives of the incident commander. It provides support staff to handle duties such as communication, fire behavior modeling, and map- and photo-interpretation. Again in the U.S., management coordination between fires is primarily done by the National Interagency Fire Center (NIFC)^[6]

U.S. Fire Size Class[2]
A	B	C	D	E	F	G
0-1/4 acre	1/4-10 acres	10-99 acres	100-299 acres	300-999 acres	1000-4999 acres	5000+

Specific agencies and different incident management teams may include a number of different individuals with various responsibilities and varying titles. A fire information officer (IFO) generally provides fire-related information to the public for example. Branch chiefs and division chiefs serve as management on branches and divisions, respectively, as the need for these divisions arise. Investigators may be called to ascertain the fire's cause. Prevention officers such as forest rangers may patrol their jurisdictional areas to teach fire prevention and prevent some human-caused fires from happening to begin with.^[2]

Communication

Information may be communicated on fires in many forms. Radios, vocals, visual signals such as flagging and mirrors, literature such as an IAP or incident action plan, whistles and mobile touch-screen computer terminals are some examples.^[7] The USFS Visual Signal Code system provides symbols used to communicate from ground to air, while aircraft may use wing tilting, motor gunning or circling to communicate air-to-ground.^[2]

Tactics

Operating in the U.S. within the context of fire use, firefighters may only suppress fire that has become uncontrollable. Conversely, fires or portions of a fire that have previously been engaged by firefighters may, by management's decision, may be treated as fire use situation and be left to burn unfettered.

All fire suppression activities are based from an anchor point (such as lake, rock slide, road or other natural or artificial fire break). From an anchor point firefighters can work to contain a wild land fire without the fire outflanking them.

Large fires often become extended campaigns. ICPs or incident posts are temporary fire camps and are constructed to provide food, showers, and rest to fire crews.

Weather conditions and fuel conditions are large factors in the decisions made on a fire. Within the U.S., the Energy Release Component (ERC) is a scale relating fuel energy potential to area. The Burning Index (BI) relates flame length to fire spread speed and temperature. The Haines Index (HI) tracks stability and humidity of air over a fire. The Keeth-Byrum Drought Index relates fuels to how quickly they could ignite and to what percentage they should burn. The Lightening Activity Level (LAL) ranks lightening potential into six classes.^[2]

Fuel models are specific fuel designations determined by energy burning potential. Placed into 13 classes, they range from "short grass" (model 1) to "logging slash" (model 13). Low-numbered models burn at lower intensities than those at the higher end.

Direct attack

Direct attack is any treatment applied directly to burning fuel such as wetting, smothering, or chemically quenching the fire or by physically separating the burning from unburned fuel. This includes the work of urban and wildland fire engines, fire personnel and aircraft applying water or fire retardant directly to the burning fuel. For most agencies, the objective is to construct a fireline around all fire meant to be suppressed.

Indirect attack

Preparatory suppression tactics used a distance away from the oncoming fire are considered indirect. Firelines may be built in this manner as well. Fuel reduction, indirect firelines, contingency firelines, backburning and wetting unburnt fuels are examples. This method may allow for more effective planning. It may allow for more ideally placed firelines in lighter fuels using natural barriers to fire and for safer firefighter working conditions in less smoke filled and cooler areas. However, it may also allow for more burned acreage, larger hotter fires, and the possibility of wasted time constructing unused firelines.^[2]

Attempts to control wildfires may also include by controlling the area that it can spread to by creating control lines: boundaries that contain no combustible material. These may be constructed by physically removing combustible material with tools and equipment, or portions may be naturally occurring. Lines may also be created by backfiring: creating small, low-intensity fires using driptorches or flares. The resultant fires are extinguished by firefighters or, ideally, directed in such a way that they meet the main fire front, at which point both fires run out of flammable material and are thus extinguished. Additionally, the use of long-term fire retardants, fire-fighting foams, and superabsorbent polymer gels may be used. Such compounds reduce the flammability of materials by either blocking the fire physically or by initiating a chemical reaction that stops the fire.

Unfortunately, any method can fail in the face of erratic or high-intensity winds and changing weather. Changing winds may cause fires to change direction and miss control lines. High-intensity winds may cause jumping or spotting as burning embers are carried through the air over a fireline. Burning trees may fall and burning materials may roll across the line, effectively negating the barrier.

Mop-up

The threat of wildfires does not cease after the flames have passed, as smoldering heavy fuels may continue to burn unnoticed for days after flaming.^[8] It is during this phase that either the burn area exterior or the complete burn area of a fire is cooled so as to not reignite another fire.

Rehabilitation

Constructed firelines, breaks, safety zones and other items may damage soil systems, encouraging erosion from surface run-off and gully formation. The loss of plant life from the fire also contributes to erosion. Construction of waterbars, the addition of plants and debris to exposed soils and other measures help to reduce this.^[9]

Fires on the wildland-urban interface

"There are three categories of interface fire: The classic wildland/urban interface exists where well-defined urban and suburban development presses up against open expanses of wildland areas; the mixed wildland/urban interface is characterized by isolated homes, subdivisions and small communities situated predominantly in wildland settings; and the occluded wildland/urban interface exists where islands of wildland vegetation occur inside a largely urbanized area."^[10]

Expansive urbanization and other human activity in areas adjacent to wildlands is a primary reason for the catastrophic structural losses experienced in wildfires.^[11] Continued development of wildland-urban interface firefighting measures and the rebuilding of structures destroyed by fires has been met with criticism.^[3] Communities such as Sydney and Melbourne in Australia have been built within highly flammable forest fuels. The city of Cape Town, South Africa lies on the fringe of the Table Mountain National Park. In the western United States from the 1990s to 2007, over 8.5 million new homes were constructed on the wildland-urban interface.^[12]

Fuel buildup can result in costly, devastating fires as more new houses and ranches are built adjacent to wilderness areas. However, the population growth in these fringe areas discourages the use of current fuel management techniques. Smoke from fires is an irritant and a pollutant. Attempts to thin out the fuel load may be met with opposition due to the desirability of forested areas. Wildland goals may be further resisted because of endangered species protections and habitat preservation.^[12] The ecological benefit of fire is often overridden by the economic benefits of protecting structures and lives.^[13] Additionally, federal policies that cover wildland areas usually differ from local and state policies that govern urban lands.^[4][14]

In North America, the belief that fire suppression has substantially reduced the average annual area burned is widely held by resource managers and is often thought to be self-evident. However, this belief has been the focus of vocal debate in the scientific literature.

Equipment and personnel

Wildfire suppression requires specialist personnel and equipment. Notable examples include Smokejumpers (firefighters who parachute into remote areas) and Helicopter support.

Success of fire supression

20px	This section requires expansion.

The success of wildfire suppression techniques is debated amongst the scientific community. A number of studies (produced during the 1990s) using Ontario government fire records compared either the number of fires or the average fire size between areas with and without aggressive fire suppression policies.^[15][16] They found that the average fire size was generally smaller in areas of aggressive policy. One report, written in 1998 by Stocks and Weber, said; "Use of fire as a management tool recognizes the natural role of fire and is applied judiciously for ecosystem maintenance and restoration in selected areas."^[17] A later 2005 study concluded that "Fire suppression is (functionally) effective insofar as it reduces area burned".^[18]

Other studies have concluded that the 20th century change in the fire cycle is a result of climate change.^[19] A 1993 study by Bergeron & Archambault said: "post-'Little Ice Age' climate change has profoundly decreased the frequency of fires in the northwestern Québec boreal forest"^[20] Critics have also highlighted that small fires are virtually unreported in areas without aggressive fire suppression policies, where detection often relies on reports from settlements or commercial aircraft, leading to incorrect average fire size data for those regions.^[21]

See also

Citations

References

• de Souza Costa, Fernando; Sandberg, David (2004), "Mathematical model of a smoldering log" (PDF), Combustion and Flame (139): 227–238, retrieved 2009-02-06 
• Graham, Russell; McCaffrey, Sarah; Jain, Theresa B. (April 2004), "Science Basis for Changing Forest Structure to Modify Wildfire Behavior and Severity" (2.79MB PDF), Gen. Tech. Rep. RMRS-GTR-120, Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station: USDA Forest Service, retrieved 2009-02-06 
• Karki, Sameer (2002), Community Involvement in and Management of Forest Fires in South East Asia (PDF), Project FireFight South East Asia, retrieved 2009-02-13 
• Mitchell, Joseph W. (September 2006), "Wind-enabled ember dousing" (PDF), Fire Safety Journal, 41 (6): 444–458, doi:10.1016/j.firesaf.2006.04.002 
• Sayre, A. P. (1994), Taiga, Twenty-First Century Books, ISBN 0-0850-2830-7 Check |isbn= value: checksum (help) 
• Lua error in package.lua at line 80: module 'Module:Citation/CS1/Suggestions' not found.
• Lua error in package.lua at line 80: module 'Module:Citation/CS1/Suggestions' not found.
• Lua error in package.lua at line 80: module 'Module:Citation/CS1/Suggestions' not found.

External links

• The International Association of Wildland Fire
• Canadian Wildland Fire Information System
• The Canadian Interagency Forest Fire Centre (CIFFC)
• British Columbia Ministry of Forests Protection Branch -- FAQs
• United States National Interagency Fire Center
• Wildfire History and Ecology
• National Institute for Occupational Safety and Health - Fighting Wildfires
• Ballistic System for Fighting Forest Fire

es:Fuego prescripto

1. ↑ Forest Fire in Canada, Natural Resources Canada, 2008-06-05, retrieved 2009-05-01 
2. ↑ ^{2.0 2.1 2.2 2.3 2.4 2.5 2.6} Incident Operations Standards Working Team (Jan 2006), Incident Response Pocket Guide, PMS #461; NFES #1077, National Wildfire Coordinating Group (NWCG), pp. i–101 
3. ↑ ^{3.0 3.1} Our Trial by Fire, onearth.org, 12-1-07, retrieved 1-7-09  Check date values in: |access-date=, |date= (help)
4. ↑ ^{4.0 4.1} Interagency Strategy for the Implementation of Federal Wildland Fire Management Policy (PDF), National Interagency Fire Council, June 20, 2003, retrieved 2008-12-21 
5. ↑ Wildland Fire Policy, US Forest Service, retrieved 2008-12-21 
6. ↑ "An Integration of Remote Sensing, GIS, and Information Distribution for Wildfire Detection and Management" (PDF), Photogrammetric Engineering and Remote Sensing, 64 (10): 977–985, October 1998 
7. ↑ Hoose, Michael, Tech Tactics, Wildfire Magazine, retrieved 2009-01-21 
8. ↑ de Sousa Costa and Sandberg, 227.
9. ↑ Effects of Fire on Soils and Erosion: Erosion and Mass Soil Movement, eWater CRC's Bushfire and Catchments, retrieved 2009-01-08 
10. ↑ City of West Covina Natural Hazard Mitigation Plan: Section 9 Wildfire, City of West Covina (California, USA), retrieved 2009-07-14 
11. ↑ Wildfire Suppression: Strategies for Containing Costs (PDF), National Academy of Public Administration, September 2002, ISBN 1-57744-094-3, retrieved 2009-01-21 
12. ↑ ^{12.0 12.1} Are Big Fires Inevitable? A Report on the National Bushfire Forum (PDF), Parliament House, Canberra: Bushfire CRC, 27 February 2007, retrieved 2009-01-09 
13. ↑ Extreme Events: Wild & Forest Fire, retrieved 2009-01-07 
14. ↑ van Wagtendonk, Jan W. (2007), "The History and Evolution of Wildland Fire Use" (PDF), Fire Ecology, Association for Fire Ecology, 3 (2): 3–17, doi:10.4996/fireecology.0302003, retrieved 2008-08-24  (U.S. Government public domain material published in Association journal. See WERC Highlights -- April 2008)
15. ↑ Stocks, Brian J (1991), The extent and impact of forest fires in northern circumpolar countries, MIT Press 
16. ↑ Lua error in package.lua at line 80: module 'Module:Citation/CS1/Suggestions' not found.
17. ↑ Lua error in package.lua at line 80: module 'Module:Citation/CS1/Suggestions' not found.
18. ↑ Cumming, S.G. (2005), "Effective fire suppression in boreal forests", Canadian Journal of Forest Research, Can. J. For. Res., 35: 772, doi:10.1139/x04-174 
19. ↑ Johnson, Edward A (1996), Fire and Vegetation Dynamics: Studies from the North American Boreal Forest, Cambridge University Press, p. 144, ISBN 9780521349437 
20. ↑ Lua error in package.lua at line 80: module 'Module:Citation/CS1/Suggestions' not found.
21. ↑ Lua error in package.lua at line 80: module 'Module:Citation/CS1/Suggestions' not found.