The target system is the system that is target of the emergency
The main parts of the target system in the forest fire-fighting
domain are the fire and the environment in which the fire is burning.
To be able to extinguish a forest fire the staff need to
have knowledge about the phenomena that control the fire.
Examples of knowledge about the forest fire are forest fire concepts,
forest fire classifications, and forest fire behaviour predictions.
Forest Fire Concepts
When a fire starts to burn out from the position where it originally ignited,
it resembles a burning doughnut shape, see figure 1.
The forest fire will act as a moving line of fire rather
than a single unit.
A forest fire can be separated in some main areas,
the head, left and right flank, and the rear.
Figure 1. Forest fire part names.
There exist four basic types of forest fires: ground fire, surface fire,
mid-level fire and crown fire. See figure 2.
The staff need to know the behavioural characteristics of these
different types of fires to be able to command a successful
Is fire in grass, bushes and other small non-decomposed
martial on the ground surface.
Surface fuels are the most common carrier of forest fires.
Grass fires can spread more rapidly than fires in any other natural fuel.
Is fire in shrubs and trees either less than two meters in total
height or taller plants that have branches or foliage within
one meter of the ground surface.
A mid-level fire generates a lot of smoke and heat,
and has been the cause of much property destruction and loss of life.
A mid-level fire in a young pine tree can spread very rapidly
and develop into a dangerous situation for the fire fighters.
Is fire in the foliage, twigs and smaller branches of the overstory vegetation.
A crown fire can have a high fire spread rate.
Is fire in fallen materials and roots that are highly compacted and
partially decomposed. Ground fire spreads slowly with little or no flaming,
but with a glowing combustion that is persistent and very difficult to extinguish.
For example, dry rotten wood can glow or smoulder for weeks until it
combusts or ignites into a flame fire.
Sometimes it necessary to dig up ground fires.
Fire smoke from a ground fire can come up from the ground at a position
that is far away from the glowing or smouldering materials.
Figure 2. Fire Classification.
Forest Fire Behaviour
The ability to predict fire behaviour often marks the distinction
between the successful forest fire-fighter manager and an unsuccessful one.
Fire predictions or a fire behaviour forecast is an
estimate of the rates of spread, directions,
and other forest fire behaviour characteristics to be expected
from a particular fire and over some future time period.
The behaviour of an established fire depends principally
on the characteristics of the fuelbed,
and on the heat transfer processes influenced by wind and slope.
Forest chemistry varies markedly by species, geographic area,
season, and so on. The greatest variations are found between species.
The fuelbed can be described by fuel loading, size and moisture.
Available fuel loading is the amount of fuel that is expected to
burn under specified fire and weather conditions.
It is a valuable and often used term for planning prescribed
fires where the weather conditions are specified.
The fuel size for dead fuels larger than 1 to 2 cm in diameter have
a little influence on the fire's rate of speed, although they do
contribute their proportionate share to boust connective
intensity and reaction intensity.
Living fuels larger than 2 to 5 cm in diameter seldom burn
at all but act as heat sinks, tapping energy that otherwise
would increase fire spread.
The fuel moisture content is overwhelmingly crucial to forest fire behaviour.
On sunny days, even on well-watered sites,
leaf moisture contents will decrease in the afternoon and
recover rapidly after sunset.
Besides the fuel characteristics the weather and geography
also influence the fire behaviour.
If a fire is burning under windy conditions or on a slope,
the fire rapidly assumes an oval shape, as shown in figure 1.
The wind can be described using the classes given in figure 3.
Smoke rises nearly vertically.
Trees of pole size in the open sway gently.
The wind moves scraps of paper.
3 - 8
Trees of pole size in open sway very noticeably.
The wind extends small flags.
Dust is raised in the road.
8 - 11
Branches are broken from trees.
Inconvenience is felt in walking against wind.
11 - 14
Tree damage increases with occasional breaking of
exposed tops and branches.
Intense stress on all exposed objects.
Very difficult to walk into the wind.
Figure 3. Modified Beauford scale for estimating wind speed.
Some rules of thumb on fire behaviour phenomena that are observable for the fire-fighters are:
The greatest variations of fuel type characteristics are found between species.
Example, Young pine trees have a large rate of fire spread,
while birch trees have a slow rate of fire spread.
Fire in fuel with a diameter less that 0.5 cm have a large rate of fire spread.
Fire in fuel with a diameter larger than 2 to 5 cm have very slow rate of
Both rates of spread and flame height will vary linearly with fuel
loading in the same fuel type; when fuel loading doubles,
the rate of spread and flame height will also double.
At fuel moistures below 5 percent, fires in fine and large fuels tend to
spread at equal rates. At fuel moisture between 5 and 10 present,
fires in fine fuels spread more rapidly than those in large fuels.
Rate of fire spread will double for each 4 meters per second
increase in wind speed, in the same fuel type.
The rate of fire spread doubles for every 15° increase
in slope up to 30° and every 10° thereafter, in the same fuel type.
In an emergency organisation the staff’s subordinates are the staff’s
tool in their task of controlling the target system.
Examples of subordinate units in the fire-fighting domain
include fire-fighting vehicles, fire-fighting persons,
reconnaissance persons, and others.
The structure of a fire-fighting organisation depends on the country,
fire department, situation and many other details.
Most fire-fighting organisations are usually
a hierarchy with at least tree levels.
Typical levels are the staff, some middle level
chiefs and some operational units.
See figure 4.
The subordinate units always have a person who is responsible
for the unit's activities, for example a middle-level chief of foreman.
The middle-level chiefs can be responsible for some large
part of the organisation and located some distance from the forest fire.
The staff are usually located at a position some distance from the forest fire.
Figure 4. A three level fire-fighting organisation.
The information they get about the fire comes from some the subordinate
units or some external information sources such as weather services,
police or civilians.
An important factor in the staff’s work is the
external organisations and persons.
They are not in the fire-fighting organisation hierarchy
but can often contribute with important resources and information.
In major crisis situations the fire-fighting organisation
usually acts as a subpart of a larger emergency organisation.
The three levels in a fire-fighting organisation can be described
using Rogalski & Samurçay's (1993) view on the information
flow and task distribution in an emergency management organisation.
See figure 5.
The staff should be trained so that they can collect proper
information and co-ordinate the subordinate units so that they
can regulate the target system.
This means that the staff need to know the
characteristics of the organisation.
They must know what resources exist and how they are
related to the tasks that can be performed in the organisation.
The controlling system structure differs form organisation to organisation.
Figure 5. Operational flow and task distribution in emergency management
Examples of the kind of knowledge the members of a staff
should have about the controlling system include:
What resources exist in the organisation, what tasks can they perform,
their needs (fuel, water, etc.), their responsibilities, and so on.
Understanding the structure of the emergency organisation,
how to exchange information with other persons in the organisation,
the other persons’ information needs and goals,
and to understand the importance of shared frameworks and shared goals.
One important task is to collect information about the situation.
The staff has the responsibility to collect and distribute
information about the current situation.
The staff have the responsibility of acquiring an overall view of the situation.
They should be able to give this view to the fire-fighting organisations.
Communication in an organisation is often critical.
It is important to know the communication standards,
such as map co-ordinates system, etc.
It is important that the staff understand that in their task of
commanding and controlling they must consider the current
status of the fire-fighting units and personnel.
They must also learn to understand the social aspects in the organisation.
The commander's task in a staff is to command and control the
This means that they should collect information about the
target system and the status of the fire-fighting so that
they acquire a situation awareness and understanding of the risk status.
On this basis they should define the task,
plan and transmit orders to its subordinates in order to direct
and co-ordinate actions between the fire-fighting unit.
One way to describe the staff’s decision-making is to
use the Method for Tactical Reasoning (MTR) by Samurçay & Rogalski (1993).
Figure 6 illustrates some steps in Samurçay & Rogalski’s MTR.
Figure 6. Decision-making in the Method for Tactical Reasoning.
Perhaps more than any other single skill,
the ability to accurately predict fire behaviour marks
the distinction between the successful forest
fire-fighter and the unsuccessful one.
Beginning with a situation description from the first fire-fighter on the scene,
the tactical decisions and the disposition of forces
will be based on estimates of the future spread and intensity of the fire.
An accurate fire behaviour forecast results in fire-lines being prepared
in the right places at the right times with a minimum of resources,
thus minimising both cost and damage.
In the situation awareness process the decision maker seeks more
information to the point where he or she has enough information to
create proper situation awareness. See subpart of the RPD model by Gary A Klein (1993). figure 7.
Situation awareness depends strongly on the knowledge that the
decision maker has available.
An experienced fire fighter seeks the right information and knows
when he has enough information and how to interpret the information.
Figure 7. Situation Assessment steps in the RPD model.
When the staff receives information about the fire scene,
they size up the situation to create situation awareness.
This process can be described by three states:
analyse the current state,
analyse possible evolution, and risk analysis.
The current state consists of information such as, fire position,
geographical environment, weather, and the fire-fighting units'
positions and status.
Possible evolution describes what areas may start burning in the future.
The risks analysis connects the processes of analysing possible
fire evolution and the goal for the fire-fighting operation.
It is important for the staff to have the ability to analyse
the situation and identify the risks that exist in the
current situation or risks that may occur in the near future.
Typical factors in the situation assessment are:
The fire position and current spreading direction and speed.
Vegetation, weather and geography.
The fire-fighting units' location and status.
Positions of important objects to be saved, such as people and houses.
Positions of strategic important areas, such as areas of fast or slow burning vegetation.
Definition of Tasks
To be able to command and control the fire-fighting units,
the decision makers need to define the goals and tasks for
the nearest future activities.
The task definition contains mainly a goal definition and
the identification of possible means of achieving it.
In all systems that have complex goals there exist some priorities among the goals.
This means that the staff need to understand how they handle
the priorities in the decision process.
The basic goals in the fire-fighting domain have the following prioritisation.
Save 1) lives, 2) fire units and equipment, 3) buildings, 4) environment.
Knowledge of Method
This describes how the fire-fighting units can be used to achieve the goals.
Here are examples of knowledge about tactic and fire extinguishing techniques.
There are two basic extinguishing techniques
- use water or not, i.e. ‘the wet method’ or ‘the dry method’.
The method which does not uses water is based on a fuel removal strategy.
Besides the techniques of using water or not,
there are various tactics such as, create a fire break, make a backfire,
or use a tactic where the fire fighters are attacking the fire from
the left and right flank and working their way towards the fire head
so that they can extinguish the fire.
It is important for the decision makers to know what is appropriate
and what the risks are in using these methods.
They should know when they should use these methods.
For example, one a rule of thumb is: To first attack the
head or fastest portion of the fire, if possible.
If the fire is too intense for a frontal attack, then the
rear should be secured and a line built along both flanks
simultaneously so that the head could be pinched off.
If there are few fire-fighting units available for a flank attack,
then the fire-fighters can drop back some distance from the head
of the fire and build a sufficient firebreak to stop the fire when
it reaches the firebreak. Selecting strategy is mainly based on
forward spread speed and available fire extinguishing methods.
The following references are used on this www page.
Chandler, C., & Cheney, P., & Thomas, P., & Williams, D., (1983).
Fire in Forestry: Forest Fire Behavior and Effects. John Wiley & Sons.
New York ISBN 0-471-87442-6
Erlandsson, U. (1990).
Skogsbrand. SBF Brandförsvarsföreningen, Ystad.
Gestrelius, K. (1993).
Pedagogik i simuleringsspel : Erfarenhets-baserad utbildning med överinlärningsmöjligheter.
Pedagogisk Orientering och Debatt 100. Lund University, Sweden.
Gestrelius, K. (1998).
Simulation and training games : Experiential Learning Saab Training Systems AB.
Klein, G. A. (1993).
A Recognition-Primed Decision (RPD) Model of Rapid Decision making.
In Decision Making in Action: Models and Methods,
G. A. Klein, J. Orasanu, R. Calderwood, and C. E. Zsambok (eds.),
ISBN 0-89391-794-X, pp. 138 - 147, 1993.
Rogalski, J.,& Samurçay, R. (1993).
Analysing communication in complex distributed decision-making.
Ergnomics, 36, pp. 1329-1343. 1993.
Samurcay, R., Rogalski, J. (1993).
Cooperative work and decision making in emergency management.
In Le Travail humain, tome 56, nr.1, pp. 53-77. 1993.