Flood risk in France and the different types of floods in Inond’Act
In France, floods are one of the most impactful natural risks, more than 18.5 million people are exposed to it. According to the Caisse Centrale de Réassurance (French public insurer for natural catastrophes and exceptional risks), 59% of the compensation awarded since 1982 under the natural disasters scheme is due to flooding (€24.8 billion).
Considering the increasing intensity and variability in weather events due to climate change, costs are expected to rise in the future. This is why it is important to understand the types and dynamics of a flood.
River Overflow
When the water level of a river rises significantly, it can cause the river to leave its bed and flood the surrounding land. Water enters buildings from the basement, from doors, windows and other openings in the walls. This is the most common case.
In Inond’Act, there are 2 types of overflowing: Quick overflowing, when the water level rises and lowers in a short timespan, and Slow overflowing, when the process takes more time.
Flash Flood
Whenever there is intense precipitation, low-lying areas can be flooded by the runoff of water. Flash floods usually last less than ten hours and are particularly dangerous in heavily artificialized areas (cities, industrial districts, etc.). Water enters buildings in the same way as river overflow.
In Inond’Act, flash floods are described as Runoff.
Rising Groundwater
After prolonged precipitations and flooding, the groundwater table, the part of the aquifer that contains the most water, can be saturated and rise to the surface. In this case, clear water fills basements and infiltrates into the walls.
In Inond’Act, this scenario is Rising groundwater.
Coastal Flooding
On the coast, unfavorable weather conditions and high tide can contribute to raise the level of the sea and flood coastal areas. Moreover, coastal flooding has different dynamics and damages than freshwater flooding.
For the moment, Inond’Act does not take it into account.
Different types of flood have different associated damages.