Geoscience Reference
In-Depth Information
Canadian index. Several different indexes were developed in the world, in the
1990s. All of these different indexes have one point in common and that is that they
incorporate the same physical phenomena into the indexes, but the physical
phenomena are expressed differently. The different phenomena used include:
energy, temperature, the presence of water in the air (relative humidity, the water
deficit, saturation deficit etc), wind, and the water stress that is experienced by
vegetation. What makes the indexes different from one another is the way in which
their different variables are combined: they can be added together or multiplied,
which sometimes has a strong impact on the results that are produced.
In the 1990s, European Community research programs were developed so that
research into fires could be carried out, and as a result lots of progress was made in
this field. Some of the research programs focused on the meteorological risk indexes
during which the indexes were tested and compared with one another by
recalculating the indexes after a devastating fire. Regarding the Minerve and
MEGAFiReS research programs [VIE 94; BOV 98], they both concluded that the
Canadian index produced the best results. The problem that has hampered the
research in this field is the fact that the validation criteria used to test indexes are
taken from real fires, and mainly based on the surface area of the fire. We know that
the overall surface area of a fire depends on how violently the fire burns and also on
many other factors that have nothing to do with climate, such as position and
extension of the forest, methods used to fight a fire, and the time that has elapsed
between the start of the fire, the alert being raised, and the arrival of help, etc.
The best method to test an index is to create authentically sized test fires on
similar patches of land. However, this is not very easy to do, especially when it
comes to trying to gather information for the dangerous values of the index, which
is a dangerous process as it could lead to the creation of a fire that might go out of
control, thus leading to the necessity to get many firemen and equipment to protect
against the fires. This method is, nevertheless, the only method that can be used to
validate an index without intervention of external factors which are not part of the
specific domain that the index is supposed to represent.
8.3. Using geographical information to work out the meteorological risks
associated with forest fires
8.3.1.
The spatial model of a risk: a methodological choice
8.3.1.1.
Spatial stakes
It is not always possible to verify the accuracy of a particular index, the major
challenge that exists today is to find a solution that can be used to work out a way to
represent the location of the risks, in other words to give a spatial representation of
risk, that allows mapping.
