Geoscience Reference
In-Depth Information
The soil's water reserve has also been recreated as part of our research carried
out on July 5, 2005 (Figure 8.10). Regarding this variable, it is only possible to
work on a daily level as it is only calculated once a day, in the evening of D-1 (after
all of the water has been removed by the process of evapotranspiration during the
day). The amount of water that has evaporated during the night was judged as being
not important, and that explains the D morning reserve is equal to the D-1 evening
reserve. The map highlights the low altitudes and the proximity to the sea as two
factors that greatly influence the way in which the soil remains dry, because the
summer rainfalls falling in the region are caused by the thunderstorms resulting
from the convection currents that occur in the relief of the hinterland of the Nice
area, far from the sea. In this example, the water reserve of the soil in the French
Riviera only reaches a third of its maximum capacity of 150 mm. This is a real risk
that could lead to the creation of a fire.
(mm/150 mm)
under 40
40-60
50-60
60-70
70-80
80-90
90-100
Figure 8.10.
Recreation of the ground's water reserve, by environmental
regression, recorded in the early morning of July 5, 2005
By combining the three maps shown in Figures 8.8-8.10 and by using the risk
index equation, the result is the creation of the meteorological risk map, which can
be seen in Figure 8.11. The risk of a fire occurring ranges from zero to average
values in this case, depending on the area in question. This risk increases the closer
towards the sea the area is, or in the southwest of the department (near the towns of
Valbonne and Cannes) where it increases to severe owing to the stronger winds that
