A Wildfires is an uncontrolled burning process that spontaneously arises and spreads in the natural environment. An emergency forest fire situation is a situation that has arisen as a result of a natural fire in a certain area, which may or may not have resulted in human casualties, damage to human health and (or) the natural environment, significant material losses and violation of living conditions.
The main causes of forest fires are: human activity (up to 90% of cases), lightning discharges, spontaneous combustion of peat chips and agricultural burns in hot weather conditions or in a fire-hazardous season (the period from the moment of melting snow in the forest until the appearance of green cover or the onset of sustained rainy autumn weather).
As a result of fires occurring in the natural environment, the protective and water protection properties of forests are reduced, forests are destroyed, the atmosphere is polluted, the heat balance is disturbed, and in some cases settlements are destroyed.
- Forest fires;
- fires of steppe and grain arrays;
- peat fires;
- underground fires of combustible minerals.
Forest fire – uncontrolled burning of vegetation, spontaneously spreading through the forest territory.
Features of large forest fires:
- occur during dry periods, most often with strong winds;
- pass against the background of a massive outbreak of small and medium-sized fires;
- lasts several days;
- spread at high speed;
- the nature of burning on the edge is very diverse;
- easily overcome various obstacles and obstacles (mineralized lanes, roads, rivers);
- cause extensive smoke pollution over large areas, which impedes the actions of aviation and ground extinguishing forces.
By the nature of burning forest fires are divided into the following types:
- individual fires (dispersed in time and area);
- mass fires (individual fires that occur simultaneously);
- solid fires;
- fire storm (especially intense fire, in the zone of continuous fire, with a rising column of a fire vortex column in the center).
By area covered by fire, forest fires are divided into six classes:
- 1) sunbathing – 0.1–0.2 ha;
- 2) small fire – 0.2-2.0 ha;
- 3) a small fire – 2.1–20 ha;
- 4) average fire – 21–200 ha;
- 5) large fire – 201–2000 ha;
- 6) catastrophic fire – more than 2000 hectares.
Depending on the nature of the fire and on which elements of the forest fire spreads, the fires are divided into lower, upper and underground (soil).
The intensity of forest fires are weak, medium and strong. The intensity of combustion depends on the state and supply of combustible materials, the slope of the area, the time of day and the strength of the wind.
According to the speed of propagation of fire, lowering and riding fires are divided into steady and fleeting.
Ground fires – fires spreading over the ground cover (fallen needles, leaves, bark, deadwood, stumps), covering the lower parts of tree trunks and roots protruding to the surface; make up about 90% of the total number of forest fires. The speed of propagation of a weak ground fire does not exceed 1 m / min, the average is 1–3 m / min, and the strong one is above 3 m / min. The height of a weak ground fire is up to 0.5 m, an average is 1.5 m, and a strong one is over 1.5 m.
Lowland forest fires can be fluent and resilient. A quick ground fire is characterized by the fiery burning of the forest floor, vegetation cover, the bark of the lower part of the trees, bare roots, bushes and undergrowth. Depending on the strength of the wind, the speed of this fire ranges from a few hundred meters to 1.5 km / h; the height of the flame can reach 2 m. Stable ground fires spread slowly and are distinguished by complete flameless burning of the soil cover; sites untouched by fire, inside the fire does not remain.
High fires arise, as a rule, from grassroots, which are the initial stage of their further development. The emergence of highland fires is largely due to droughts and strong winds. A weak riding fire has a speed of up to 3 m / min, an average fire is up to 100 m / min, and a strong one is over 100 m / min.
High fires, as well as low, have a clearly defined edge, and in the wind, in addition, the rear (edge of fire moving against the wind), flanks (firing edge advancing perpendicular to the wind) and front ( firing edge most rapidly propagating in the wind direction).
The speed of propagation of riding fires reaches 25 km / h with the formation of a large mass of sparks and ignited material, flying in front of the front of fire. Mounted fires, as well as grassroots, can be steady and fleeting. With steady mounted fires, the fire moves in a solid wall from ground cover to tree crowns at a speed of up to 8 km / h, and the tree crowns burn as the edge of the lower fire advances. With a runaway riding fire, which occurs only with a strong wind, the fire spreads to the trees’ jumps, “jumping”, jumping across rivers, roads, treeless tracts, ahead of the front of the lower fire.