Forest Research Institut Baden-Württemberg (FVA)
Department of forest economics
Tel: +49 761 4018 231
Fax: +49 761 4018 333
Forest Fire Handbook
The objective of fighting a forest fire is the prevention of damage to people, property and assets. In addition it significantly contributes to environmental protection. Fundamentally, the protection and safety of the operational fire fighting force is of prime importance. Necessary fire fighting measures, which could put the rescue personnel in danger, should be limited as much as possible.
If a forest fire is first reported to fire service headquarters, they notify the rescue services and inform the forest authorities as well as forest owners.
By means of the modern sensory equipment used in forest fire early warning systems, forest fires can be quickly and accurately located. This head start can be decisive in the resulting size of a forest fire. For about 75% of forest fires in Brandenburg, 20 minutes elapses between detecting the fire and starting to put it out.
|Fig. 1: Forest fire. Photo: State of Brandenburg|
Local fire brigades extinguish most forest fires at their first attempt. Weak points in the alarm system or a breakdown in cooperation between the fire service and the forest authorities can have an impact on the size of the blaze and the amount of damage caused. Therefore regular forest fire drills, in which all the actors get to know each other and practise working together, are an essential part of forest fire fighting and prevention.
If a fire can not be extinguished at the first attempt then additional personnel and resources must be notified and brought to the site of the fire. If the extent of the fire makes it necessary to split the fire fighting forces into divisions, then an operational headquarters is established. The operational manager is the fire chief who is the first to arrive at the scene.
Fire fighting is coordinated through the operational headquarters (emergency services centre or operations centre) from a central location (command vehicle or previously determined space), which is not directly located at the endangered site. The manager directs all actions to combat threats, in particular the effective deployment of fire fighters at often unknown locations. Hence, the manager must quickly ascertain and evaluate the situation. S/He has to be able to rely on information and recommendations from the operational headquarters. The relevant local forest official must also be part of the operational headquarters team, as s/he has precise knowledge of the forest area.
The operational headquarters has the following duties:
In contrast to building fires, the priority in forest and wild fires is to prevent the fire from spreading. In the rarest of cases, sites can be completely extinguished. The fire fighting strategy predominantly aims to contain the fire.
Fig. 2: A fire on a hillside has
|Fig. 3: Ground fire. Photo: S. Kaulfuß|
Forest and wildfires typically form roughly in the shape of an ellipse. Burning only occurs in the area of the perimeter of the ellipse. The fire flanks found to the right and left of the wind direction spread noticeably slower than those in the direction of the wind – the so called fire front or hot spot. If the wind changes direction, the flanks can quickly become the fire front.
It is important to assess fires on terrains such as mountainous areas. Along with the danger that fire personnel could fall, fire fighting on slopes and in valleys demand particular expertise. Generally a forest fire in a mountainous terrain spreads uphill very rapidly. This is caused by the upward flowing hot air and warm thermals. Higher growing, stunted vegetation is readily desiccated by the approaching fire. Furthermore, fires can be rekindled again and again by rolling and burning forest material.
The most important objective is to prevent the fire jumping from the ground into the tree canopy and hence starting a crown fire. It is possible to fight flame lengths up to 1m above the ground with fire beaters. Fire perimeters with flames the height of a person (1-2m) are fought with water jets along with backpack sprayers and shovels. Putting out flames higher than 2-3m is not possible using hand held equipment. With flames greater than 3m there is a danger of an aerial fire and therefore an increased risk of fire islands caused by firebrands. Due to the rising hot air, sparks of pinecones, moss, charcoal or birch bark tar can be lifted up and carried to ignite new fires up to 400m ahead of the fire front. In this manner flying sparks allow even wide strips of deciduous forest to be jumped.
In order to fight a forest fire successfully, a thorough survey of the site is a must. The key focus areas are determined according to the following tactical priorities:
When investigating the type of fire (crown, ground or surface fire), geographic and topographic particulars (main direction of spread of blaze, terrain specifics, entry and escape points for water tenders, wind direction and any expected changes) also play an important role. Conclusions can also be drawn about the fire by observing the column of smoke (already when driving to the site). The colour and form of the column of smoke provides information about the fire’s behaviour.
Based on all this information a decision is made during the operational planning about how the fire will be fought. A defensive or offensive method of fire fighting is possible.
Common fire fighting practice in Germany is a direct offensive attack on a fire front by means of fire fighting crews, fire engines and/or air tankers. An approach against the wind at the fire front is the most effective, but because of the difficulty in predicting the speed at which the fire is spreading, is not without risks. This method can only be applied at low flame heights. The danger to people is high if the speed of the fire and flame lengths has been falsely estimated. Increasing wind speeds and hard to manage topographical conditions can lead to fire services being enclosed by fire. Furthermore fire crews are exposed to the heat of the fire and smoke.
If a direct attack is not possible, because the flames are too high to tackle or the surface is contaminated with ammunition, then these blazes are fought defensively. By creating fire breaks (fire lines) or using existing fire resistant barriers (streets, paths) the fire should be able to be halted. Fire breaks can even be laid in advance allowing straight fire lines to be created. Along with the positive benefit of working without heat or smoke stresses, this method also has disadvantages. They include the increased workload and the danger posed to the fire crews by working without visual contact with the fire perimeter. Furthermore fires are able to jump these fire breaks and surveillance of the land lying behind them is required. It is important while fire fighting (defensive as with offensive) to monitor the surrounds and immediately put out any fire islands caused by sparks or firebrands.
Establishing firebreaks is generally only sensible when intensive aerial fires are to be stopped. In most cases the immense personnel and material effort required (clearing tools, staff etc.) can be more effectively used in an offensive procedure. However, their establishment can always be seen as a Plan B in order to safeguard the operational success of an offensive approach. Coordination with the relevant forest officials and forest owners must occur before their construction. Creating firebreaks usually requires using large equipment. Forestry and agricultural machinery as well as bulldozers or military armoured recovery vehicles can be used to undertake the scarification (exposing the mineral soil layer). Firebreaks are always created in two pieces with a vegetation free scarified strip and an observation area lying behind it. The scarified strips should be so created that they are twice as wide as the expected flame length.
must be adhered to when extinguishing fires on military training areas (current
or former) and on former battlefields (e.g. WWII). Fire accelerants and
explosions increase a fire’s intensity. Close cooperation between the fire
service and local and expert advisers like the army and forest personnel is
important. Fire fighting on ammunition contaminated takes place at a safe
distance or at strategically important points. In most cases these fires are
fought indirectly or from the air. One waits until the fire reaches “non-dangerous”
areas and then it is extinguished there. Areas contaminated with ammunition
which are ablaze can not be driven over with conventional fire engines. Hence,
specially protected fire engines are used in such fire fighting. Active
military exercise areas have their own fire service and/or some armoured
vehicles which can be deployed.