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A bushfire (also known as a Wildfire in the USA and Canada) is a fire that occurs in the bush (collective term for scrub, woodland or grassland of Australia, New Zealandmarker, New Caledoniamarker). In south east Australia, bushfires tend to be most common and most severe during summer and autumn, in drought years, and particularly severe in El Niño years. Southeast Australia is fire prone, and warm and dry conditions intensify the probability of fire. In the north of Australia, bushfires usually occur during the dry season (April to September), and fire severity tends to be more associated with seasonal weather patterns. In the southwest, similarly, bushfires occur in the summer dry season and severity is usually related to seasonal growth. Fire frequency in the north is difficult to assess, as the vast majority of fires are caused by human activity, however lightning strikes are as common a cause as human ignited fires and arson.

History

The natural fire regime was altered by the arrival of humans in Australia. Fires became more frequent, and fire-loving species — notably eucalypts — greatly expanded their range. It is assumed that a good deal of this change came about as the result of deliberate action by early humans, setting fires to clear undergrowth or drive game.

Plants have evolved a variety of strategies to survive (or even require) bushfires, (possessing reserve shoots that sprout after a fire, or developing fire-resistant or fire-triggered seeds) or even encourage fire (eucalypts contain flammable oils in the leaves) as a way to eliminate competition from less fire-tolerant species. Many native animals are also adept at surviving bushfires.

Bushfire control

Key factors affecting bushfires

• Fuel: Anything that burns is fuel for the fire: litter on the ground (leaves, twigs, rubbish), undergrowth (shrubs, grass, seedlings), trees and other vegetation, structures (such as houses) and any other miscellaneous objects in the vicinity; gas bottles, piles of firewood, tyres, etc. Ladder fuels are low growing (30 cm to 2 metres) vegetation that offers a ladder for the fire to rise to the canopies of trees.

• Weather: Weather is a major contributor to bushfires. The hotter and dryer, the more likely it is for a bushfire to start and spread uncontrollably. High winds will reduce humidity, and cause an ongoing bushfire to spread more rapidly. Most bushfires start in the afternoon, when it is driest and hottest.

• Topography/slope: The topography of the terrain is a major factor in bushfire behaviour. Generally the fire spreads faster uphill. Conversely, fire going downhill advances more slowly. The superheated air is pushed in front of the fire drying and pre-warming the fuel for ignition. When a fire progressing downhill hits the flat at the bottom of the hill, the height of the flame can quadruple, when the fire hits the undulating slope opposite, the height may quadruple again. In other words, 1 metre flames going downhill can turn into 4 metre flames at the bottom of the hill, and to 16 metre flames starting to climb the next hill. While the height of the flame depends mainly on the height of the fuel, the former stands as a reminder that an innocent looking small bushfire can rapidly change into a life threatening fire.

Firefighting methods

In National Parks and reserves, bushfire fighting is carried out by professional staff, such as Rangers, Park Workers, Field and Technical Officers, with help from volunteers from rural areas. The rural areas have bush fire services, such as the CFA (in Victoria), the RFS (in NSW), largely staffed by volunteers, to help control bushfires. As with large fires on public land it is common for Parks staff and Rural or Country volunteers to work together on large rural fires. On some occasions urban firefighting professionals are also called in to assist. As well as the water-spraying trucks commonly used in urban firefighting, bushfire services often own or lease aircraft, particularly fire helicopters, that can douse areas inaccessible to ground crews. However, large fires are often of such a size that no conceivable firefighting service could attempt to douse the whole fire directly, and so alternative techniques are used.

Typically, this involves controlling the area that the fire can spread to, clearing control lines which are areas which contain no combustible material. These control lines can be produced by bulldozing, or by backburning — setting a small, low-intensity fire to burn the flammable material in a controlled way. These may then be extinguished by firefighters, or, ideally, directed in such away so that they meet the main fire front, at which point both fires will run out of flammable material and be extinguished.

Unfortunately, such methods can fail in the face of wind shifts causing fires to miss control lines, or because fires jump straight over them (for instance, because a burning tree falls across a line, or burning embers are carried by the wind over the line).

The actual goals of firefighters vary. Protection of life (both the firefighters and civilians) is given top priority, then private property according to economic and social value. In very severe fires, this is sometimes the only possible action. Protecting houses is regarded as more important than, say, machinery sheds, though firefighters, if possible, will try to keep fires off farmland to protect livestock and fences (steel fences are destroyed by the passage of fire, as the wire is irreversibly stretched and weakened by it). Preventing the burning of publicly owned forested areas is generally of least priority, and, indeed, it is quite common (in Australia, at least) for firefighters to simply observe a fire burn towards control lines through forest rather than attempt to put it out more quickly — it is, after all, a natural process.

The risk of major bushfires can be reduced by reducing the amount of fuel present. In forests, this is usually accomplished by conducting hazard reduction controlled burns — deliberately setting areas ablaze during favourable weather conditions in spring or autumn. Controlled burns can be controversial, both because they can be regarded as tampering with the forest ecosystem, and because serious fires can be started if a control burn gets out of hand. The Australian Aborigines used controlled burning to encourage new growth of plants in some areas.

Contrary to urban understanding of bushfire, rural farming communities are comparatively rarely threatened directly by them. They are usually located in the middle of large areas of cleared, usually grazed, land, and in the drought conditions present in bushfire years there is often very little grass left. However, urban fringes often spread into forested areas, and communities have literally built themselves in the middle of highly flammable forests.

On occasions, bushfires have caused wide-scale damage to private property, particularly when they have reached such urban-fringe communities, destroying many homes and causing deaths.

People living in fire-prone areas typically take a variety of precautions. These include building their home out of flame-resistant materials, reducing the amount of fuel near to the home or property, constructing firebreaks and investing in firefighting equipment.


Significant bushfires

Notable bushfire events

Fire Location Hectares Burned Date Deaths Properties Damaged
Black Thursday bushfires Victoria, Australiamarker approximately 5 million ha 6 February 1851 about 12 1 million sheep; thousands of cattle
Red Tuesday bushfires Victoria 260,000 ha 1 February 1898 12 2,000 buildings
1926 bushfires Victoria February – March 1926 60
Black Friday bushfires Victoria 2,000,000 ha December 1938 – January 1939, peaking 13 January 1939 71 3,700
1944 Bushfires Victoria estimated 1 million ha 14 January – 14 February 1944 15–20 more than 500 houses
1951-2 Bushfires Victoria Summer 1951–52 at least 10
Black Sunday Bushfires South Australiamarker 2 January 1955 2
1961 Western Australian bushfires Western Australiamarker January–March 1961 0
1962 bushfires Victoria 14–16 January 1962 32 450 houses
Southern Highlands bushfires New South Walesmarker 5–14 March 1965 3 59 homes
Tasmanian "Black Tuesday" bushfires Tasmaniamarker Approximately 264,000 ha 1967 62 1,293 homes
1969 bushfires Victoria 8 January 1969 23 230 houses
Northern Sydney bushfires Sydneymarker, NSW 1979
Ash Wednesday bushfires South Australia and Victoria 418,000 ha 16 February 1983 75 about 2,400 houses
1994 Eastern seaboard fires New South Wales 27 December 1993 – 16 January 1994 4 225 homes
Dandenongs bushfire Victoria 21 January 1997 3 33 homes
Lithgow bushfire New South Wales 2 December 1997 2
Linton bushfire Victoria 1998 5
Black Christmas New South Wales 740,000 acres 2001–02 0 121 homes
2003 Canberra bushfires Canberramarker, Australian Capital Territorymarker 2003 4 almost 500 homes
2003 Eastern Victorian alpine bushfires Victoria over 1.3 million ha 8 January – 8 March 2003 41 homes
Tenterden Western Australiamarker December 2003 2
Eyre Peninsula bushfire South Australiamarker 145,000 ha 2005 9 93 homes
2006 Central Coast bushfire Central Coast, New South Walesmarker New Years Day, 2006
Jail Break Inn Firemarker Junee, New South Walesmarker 30,000 ha New Years Day 2006 0 Livestock losses estimated to be over 20,000. Seven homes, seven headers and four shearing sheds destroyed. of fencing damaged.
Stawell New year fire Victoria December 2005 – January 2006
Grampians Bushfire Victoria January 2006 3
Pulletop bushfiremarker Wagga Wagga, New South Walesmarker 9,000 6 February 2006 0 2,500 sheep and 6 cattle killed, 3 vehicles and 2 hay sheds destroyed as well as 50 km of fencing.
2006-07 Australian bushfire season September 2006 – January 2007
Kangaroo Island Bushfires South Australia 95,000 ha 6–14 December 2007 1
Black Saturday bushfires Victoria 450,000+ ha 7 February 2009 – 14 March 2009 173 2,029+ houses, 2,000 other structures


Bushfire gallery

Image:Gippsland, Sunday night, February 20th, 1898.jpg|A painting depicting the Red Tuesday bushfires at Gippsland.Image:Wagga Wagga, Pulleytop bushfire, February 6th, 2006.jpg|The Pulletop bushfiremarker at Wagga Waggamarker.Image:UminaFire1.JPG|One of the blazes of the 2006 Central Coast bushfires on New Years Day, 2006. Photo taken at Umina Beachmarker.Image:Smoke_from_fire_near_holbrook_NSW.jpg|Smoke from the bushfire near Holbrookmarker on 2 February 2007.

See also

Notes and references

  1. Flannery, T. (1994) "The future eaters" Reed Books Melbourne.
  2. Wilson, B., S. Boulter, et al. (2000). Queensland's resources. Native Vegetation Management in Queensland. S. L. Boulter, B. A. Wilson, J. Westrupet eds. Brisbane, Department of Natural Resources.
  3. White, M. E. 1986. The Greening of Gondwana. Reed Books, Frenchs Forest, Australia.
  4. Black Thursday. Retrieved 10-2-2009.
  5. ABS. Retrieved 10-2-2009.
  6. Norther Daily Leader, "Some past bushfires in Australia, p.3, 10 February 2009


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