Grassroots call a fire when it burns. Horse fire. Origin, distribution, methods of extinguishing. Leaving the fire zone
1. Classification of fires by zones of distribution
From the point of view of the production of work related to localization, fire extinguishing, saving people and material values, the classification of fires is carried out in three main areas:
- individual fires
- massive and continuous fires
- fires and decay in rubble.
Natural fires are:
As indicated above, the priority areas, as the most vulnerable, are located at the junction between urbanized areas and wooded areas. Better prevention should consist in stricter control of land use and urbanization. The second aspect of prevention in these areas is the creation or maintenance of agriculture or pastoralism that will support rain-fed areas. But the preservation of rural activity, and therefore of the population, has social costs.
What is true for forest fires is also designed to prevent flood or avalanche risks. Is the direct cost of such an incentive related to direct compensation for natural disasters? This is a sustainable development issue. But what political personalities will have this courage when the only resilience to which they are attached is their mandate?
- forest
- peat
- steppe (field)
All forest fires are extremely dangerous, since by the beginning of localization they, as a rule, have time to cover large areas, and the means of struggle are not enough. Especially terrible are the massive fires that occur in dry weather, and their total area is hundreds of thousands of hectares. In this case, there is a threat of destruction by fire settlements and objects of the national economy located in forests, as well as strong smoke and gas pollution even in large settlements far from forests.
Forest fire prevention is based mainly on the provisions of the Forest Code and a number of other specific texts. The provisions of the Forestry Code, which are of an administrative and repressive nature, do not in any way prejudice provisions of general interest or urgency that fall under the General Code of Local Authorities or the Country Code.
These documents document the measures already taken to protect forests from fire and assess their effectiveness. The texts arising from the Forest Code do not allow acting on the basis of soil law. They were established by law on February 2. These include old plans for areas susceptible to forest fires.
Zone of individual fires is an area where fires occur on selected sites... Such fires are dispersed throughout the area, so there is a possibility quick organization their mass extinguishing.
Zone of massive and continuous fires- an area where there are so many fires and fires that it is impossible for the relevant units to pass or find in it without carrying out localization or extinguishing measures; and the conduct of rescue operations is practically out of the question.
Such zones arise under certain conditions: continuous development of a forest, a large amount of combustible materials, etc.
The resulting normative map is a synthesis of these two maps. Fighting moderate forest fires is generally satisfied with conventional forestry equipment. But this equipment turns out to be inadequate in the event of large fires, strongly fueled by strong winds. To fight these great fires, green spaces or battle lines must be prepared in advance. Moreover, these hardware are expensive when to build them and much more when they need to be maintained. For example, clearing should be updated periodically; this operation is time-consuming and labor-intensive, regardless of the technique used, and ultimately offers only limited protection.
A special form of continuous fire is a firestorm.
It is characterized by flows resulting from the combustion of a large amount of materials and forming a convection flow (column), towards which air masses rush at a speed of more than 15 m / s.
The formation of a fire storm is possible when following conditions:
- the presence of building or spreading flammable liquid on an area of at least 100 hectares.
- relative humidity less than 30%
- availability a certain amount of combustible materials on the corresponding area - in terms of wood, about 200 kg / m2 on an area of 1 km2.
In addition, in the long term, clearing provides negative impact on the stability and regeneration of some forest formations. Here are some of the reasons why foresters come up with solutions that rely more on informed and adapted forestry practices.
Existing, for example, pruning of low branches that do not participate in photosynthesis, by removing the relay between the shrub or grass layer and the tree layer, give nice results... The tree can be spread up to 60% of its height without slowing down its growth. Deciduous trees will be flanked to the trunk, resinous, due to the risk of resin loss, will be flanked up to 10-20 cm from the trunk. Maintaining undergrowth with mechanical equipment or controlled burning is facilitated on a well-groomed stand.
The zone of fires and smoldering in the rubble is characterized by strong smoke and prolonged (over 2 days) burning in the rubble. The use of the relevant units is limited due to the danger to human life due to thermal radiation and the release of toxic combustion products.
Such smoke is considered dangerous on open area, at which the visibility does not exceed 10 m. The concentration of carbon monoxide in the air of about 0.2% causes fatal poisoning within 30-60 minutes, and 0.5-0.7% - within a few minutes.
It was found that the fueling of the stand was highly dependent on the density of the canopy. The dense coating reduces flammability and combustibility by acting on two factors: microclimate and vegetation structure. The dense forest cover creates a forest atmosphere characterized by low wind speeds on the ground. For example, with a dense cover of green oaks, even in a strong mistral, the air is calm. If the current fire penetrates under such a stand, it will not be blown up by the wind and it will be easier to fight.
In addition, in a dense canopy, humidity on the ground or air remains high, which favors the growth of Skeaphile species, which are usually not very flammable. It happens that even a fire is self-extinguishing, when it penetrates such masks, both grassy and muscle layers are not very easily ignited.
Features of large forest fires:
- occur during dry periods, most often with strong winds
- take place against the background of a massive outbreak of small and medium fires
- last for several days
- spread at high speed
- the burning behavior at the edge is very varied
- easily overcome various obstacles and obstacles (mineralized strips, roads, rivers ...)
- cause strong smoke in large areas, which impedes the actions of aviation and ground forces.
Finally, little solar radiation penetrates under the dense canopy. During periods of persistent drought, undergrowth plants suffer much less drying out and are therefore less flammable. The forest environment created by the dense canopy has an important influence on the structure of the vegetation. Firstly, the biomass of Sophilic stands is usually low, then due to the content of a certain moisture, the litter decomposes better and faster, finally, low branches, devoid of light, destroy, thereby contributing to the natural pruning of woody vegetation.
Forestry regeneration. In the immediate aftermath of a fire, soils without vegetation are at risk of severe erosional events that could render them unsuitable for reforestation. The first priority is to ensure that the soil does not suffer too much during the first rains, especially if the grass cover has not yet settled. Most effective method soil protection, especially on slopes, is the implementation of fascines, in situ, with burnt vegetation. These foci, by trapping materials carried by the rains, will create reserves of deep and mobile soil favorable for transplanted species.
2. Types of forest fires and their distribution
Depending on the nature of the fire and on which elements of the forest (forest composition) the fire spreads, forest fires are subdivided into:
- grassroots
- - riding
- underground (soil)
A grassland fire is a forest fire that spreads over the soil cover.
The second priority is sanitary, as the passage of fire usually affects only the smallest branches. The first task of foresters is to check for fire damage to the cambial layers of the trunk and large branches, and if they are severely damaged, it is better to collect deciduous trees that will discard stumps or continue, if planting is only achieved in certain areas, to the healing size of the affected parts. For those who do not drink stumps, they need to be killed. To do this, some of them, as a result of survival, can produce cones and seeds and act as seeds for the last time.
Ground fires are of two types: fugitive and sustained.
A fire is called a runaway, in which the ground cover, fallen leaves and needles burn ..
A sustained fire is a fire in which after the burning of the cover litter, stumps, dead wood, etc. It usually develops in the summer, burning continues for a long time. Conditions for the development of crown fires can develop here. For grassland fire characteristic elongated shape fires with an uneven edge. Smoke color in a ground fire is light gray.
In the long term, trees affected by fire suffer and, like all diseased trees, their defenses are weakened. Phytosanitary risk becomes predominant. Trees that are prey to xylophages or fungi must be carefully monitored. These diseased trees can become hotbeds of epidemics that can spread to healthy trees in neighboring areas.
What is a wildfire?
Of course, it will need to be renewed. Natural supersaturation has limitations and, above all, can hardly offer spontaneously a duality covered with a tight lid, durable. In addition to forests in the strict sense, fires concern small subcontract formations, mainly tree formations or secondary formations.
At night, the rate of fire propagation is slower than during the day.
The rate of spread of ground fires in all directions is not the same and depends on the speed and direction of the wind, the uneven distribution of combustible materials, their moisture content, and other factors. The wind speed almost completely determines the contour of the fire. The stronger the wind, the more elongated the fire contour in its direction.
As a rule, the most favorable period for forest fires is southern winter due to the combined effect of drought and low soil moisture, the influence of trade winds. The prefectural order prohibiting fires within 200 m of the forest establishes a sensitive period from August 15 to January 15.
Fire can take three forms depending on the characteristics of the vegetation and climatic conditions in which it develops. The so-called "bonfires" or "bonfires" burn the organic matter contained in the litter: they usually interfere with the stands of tamarind or brands and may be interested in the thickness of almost half a meter, Incandescent lamps with burning, their propagation rate is low, sometimes undetectable, and a delay in re-emergence surface fire can range from hours to weeks, making it difficult to fight.
By the speed of propagation and height of the flame, ground and top fires are divided: strong, medium and weak (Table 2)
table 2
Fire parameters |
Values of indicators of fire strength |
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middle Surface fires burn the lower layers of vegetation, that is, the upper part of the litter, herbaceous layer and low wood mass, and are usually propagated by radiation with sufficient energy to communicate the fire to the upper layers of vegetation. The crown fire burns the top of the trees and forms a crown of fire. They tend to emit a large number of energy and have very high propagation speeds. They are all the more intense and difficult to control because the wind is strong and the fuel is dry. Consequences for people, property and the environmentThe rate of fire propagation is slow in soil, medium to high on the surface, and much higher in tree crowns. Populations and assets are currently at low risk of wildfire, although this risk increases with increasing urbanization. However, there is a problem with the intervention conditions, which are sometimes technically difficult in access conditions that are not suitable for driving. |
strong |
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Grassland fire |
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Flame height m |
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Horse fire |
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Fire propagation speed m / min That's why natural environments most vulnerable to this risk: the biological diversity of plants and animals in the Réunion environment undoubtedly has a very high generic value and constitutes a controlling stake. But the forest presents other problems. Soil erosion by limiting direct erosion. Risk of bushfire on Reunion IslandPreservation of water retention capacity. Conservation of landscapes and the potential for public recognition and ecotourism. Contribution to the woodworking industry through the production of wood-based material. The risk of fire depends on the nature of the vegetation as well as the climatic conditions. In general, the average high risk level applies to 60% of the forest area. |
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Underground fire |
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Burning depth, cm |
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Riding forest fires are characterized by the combustion of the above-ground cover and the forest stand. These fires arise from grass-roots as a further stage of their development, and the grass-roots fire is part of riding fire.
In Reunion, the greatest potential risk is in the western region, where the most tall trees and the most flammable plant species. This is largely due to the nature of the climate, as this is the area where rainfall is least abundant on the island and where the dry season is long and very noticeable.
On average 10 fires a year and a big fire every 20 years. The area covered by fires is 56 hectares in case of occurrence, reflecting the poor strong disparity between regions: the ominous western average is 250 hectares, while elsewhere it lies between 3 hectares and 88 hectares.
Dense coniferous young stands are most susceptible to riding fires. Strong winds and steep slopes contribute to their occurrence if a ground fire spreads uphill. Riding fires are more likely to occur in summer when drought is combined with winds.
Distinguish fugitive and sustained crown fires.
At sustained fires tree crowns are burned as the edge of the ground fire advances. Combustion does not advance independently along the canopy. Such fires can be called rampant.
The average fire is 7 ha, ranging from 1 ha to 700 ha. The number of fires per year is on the order of: Thus, during this period, there is a noticeable progress compared to the one that precedes it, thanks to the implemented equipment and better coordination of interventions. But at the same time, there has been a noticeable increase in the number of shooting in urban or suburban areas.
In the event of forest fires, there are two zones: the leeward zone and the wind zone. 
It stretches from Saint Denis to Tampon and is very sensitive to fires. Most sensitive areas. Coastal areas where most fires start and develop over large areas.
At runaway riders In case of fires, the spread of combustion along the canopy can outpace the advance of the edge of a ground fire. In windy weather, mainly runaway top fires occur, when the fire spreads over the forest canopy and outstrips the base fire.
Riding fires are accompanied by the release of a large amount of heat. Therefore, crown fires affect the atmosphere much more strongly than ground fires. Heated air and combustion products cause upstreams and the formation of convective columns several hundred meters in diameter. Their forward movement coincides with the direction of advancement of the fire front. The flame in the middle of the column can rise to a height of 120 m. The convective column increases the air flow into the fire zone and generates wind, which intensifies the fire. This particular form of continuous fire is called fire storm.
Forest soil (underground) is the flameless combustion of the upper peaty soil layer. The stand is completely destroyed due to exposure and burning of tree roots. Soil fires are observed in areas with peaty soils. The accumulation of peat in a certain area in the form of layers that are homogeneous or different in nature and thickness is called a peat deposit.
Peat- a young geological formation, arising as a result of the withering away of marsh vegetation with an excessive amount of moisture and insufficient air access. Peat gradually decomposes under the influence of temperature, humidity and other factors. The higher the degree of decomposition of peat, the more it is subject to fire
Peat can ignite throughout the year, but most often in the second half of summer, when it dries up. Spontaneous combustion of peat occurs as a result of self-heating, as well as ignition due to sparks from fire sources and operating machines, lightning discharges, etc.
Depending on the depth of burning underground fires are divided into strong, weak and medium (table 2).
A natural disaster in which fire is almost impossible to control and which spreads over forest areas is called a forest fire. Forest fires it is customary to divide into natural and anthropogenic. The most common fires are those caused by lightning strikes. Forest fires are sometimes so large that they can be seen even from space. Fires caused by lightning strike most often occur in old forests, as old trees have much more dry branches than young ones. Therefore, in young forests, there are practically no fires from a lightning strike. Thus, a kind of balance existed in nature long before the appearance of man. Old forests burned down, and young green ones grew in their places. This was the ecological role of forest fires.
According to statistics, the share of natural forest fires in the world is 7-8% of total mass natural fires. Most forest fires are related to human activities. So there is an urgent need to work fire services, monitoring compliance fire fighting equipment safety and compliance with fire safety laws.
Controlled fires are called fires that are artificially caused. The purpose of such fires can be: the fight against insects and forest diseases, the preparation of the forest for the further planting of seedlings, the removal of logging waste, as well as deliberate arson of the forest for the purpose of its subsequent felling.
Fires are divided into ground and top fires.
At grassland fire forest litter, lichens, mosses, grasses, branches that have fallen to the ground, etc. are burned. The speed of movement of such a fire is 0.25-5 km / h downwind. The height of the flame reaches 2.5 m. The combustion temperature is about 700 ° C (sometimes higher). Ground fires are fugitive and persistent: at the first, the upper part of the ground cover, undergrowth and undergrowth burns out. Such a fire spreads at high speed, bypassing places with high humidity, therefore, part of the area remains unaffected by fire. Second, runaway fires mainly occur in the spring, when only the uppermost layer of small combustible materials dries out. A riding forest fire covers leaves, needles, branches, and the entire crown, can cover (in the event of a general fire) the grass-moss cover of the soil and undergrowth. Propagation speed from 5-70 km / h. Temperature from 900 ° C to 1200 ° C. They usually develop in dry, windy weather from a ground fire in stands with low-shed crowns, in stands of different ages, as well as in abundant coniferous undergrowth.
Horse hurricane fires arise from strong wind, they are very dangerous for their enormous propagation speed, which can reach a maximum speed of 70 kilometers per hour. An indiscriminate fire is dangerous in that it burns out the forest completely, as the fire spreads in a vertical wall from the soil to the very tops of the trees. The speed of such a fire is approximately 8 kilometers per hour.
Crown fires are very dangerous and very difficult to extinguish, since a large number of sparks are formed on the tops of the trees, which fly ahead of the main fire and form ground fires hundreds of meters in front of the main focus.
Forest fires can occur as a result of the draining of swamps due to peat fires. Such fires are called underground or soil, the speed of such fires is 1 kilometer per hour. Such fires can spread to a depth of several meters, as a result of which they are hardly noticeable. The difficulty in extinguishing such a fire is that peat can burn under water and without air access. We need preliminary reconnaissance for such forest fires.
