CARDS. Climate risks: which are the most exposed areas in mainland France?

April 4, 2019 by No Comments

Not only does global warming provide the conditions for unstable weather, it also increases the frequency of serious events.


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“We will be there.” Emmanuel Macron puts his hand on the shoulder of the victims, shocked and exhausted. To those who lost their homes, swept away by the flooding of the Vésubie or Roya, innocent rivers of the Nice hinterland transformed into monsters of mud by the record rains of the storm Alex, the President of the Republic promised Wednesday October 7 “several hundred million euros”. To rebuild. “Very quickly.” The same morning, 55 municipalities were declared in a state of natural disaster. Five people died. Around twenty are missing or “supposedly missing”. Traumatized, some want to leave their valley. Many have no other choice.

Storms, erosion, land movements, heat waves, drought, avalanches … The vast majority of the territory, in metropolitan France as well as overseas, is exposed to one or more natural risks likely to have serious consequences on a territory , its people and its economy. While climate change provides the conditions for unstable weather, franceinfo has focused on three indicators that affect disparate regions of mainland France: floods, forest fires and land movements.

To find out the risk (s) to which your municipality is exposed as well as its exposure index, enter its name in the search engine below.

Multiple risks throughout the territory

In January, the Ministry of Ecological Transition released a report on France’s vulnerability to climate risks (PDF), based on data for the year 2016. At the time, six in ten French people were exposed to at least one of these risks: iflooding, forest fires, avalanches and atmospheric phenomena.

The risk of flooding is the most widespread: it concerns 64% of the municipalities, in particular because of the“historic settlement of towns along waterways, then used as transport routes and reinforced since”. A finding that “also applies to coastal areas, faced with ever increasing urbanization, in connection with tourist pressure”.

The flood risk map:

The risk of forest fires mainly concerns the municipalities of Provence-Alpes-Côte d’Azur, Corsica, Languedoc-Roussillon, Drôme, Ardèche and the Aquitaine region.

The forest fire risk map:

In addition, 55% of municipalities are exposed to a risk of land movements. Clay soils are particularly vulnerable when they are weakened by the alternation of drought and rainfall. As widespread as it is little publicized, because less spectacular than a mudslide rolling down a valley or a wall of flame licking the surroundings of a seaside resort, this clay shrinkage-swelling phenomenon affects both the north of France and Brittany, the Grand-Est and the south of the country.

The risk map of land movements:

Population density, land use planning, socio-economic context, demographic profile and, of course, the occurrence of an extreme meteorological episode are all factors likely to transform a hazard (a major rainfall phenomenon, for example ) in disaster. “It is a conjunction of elements”, explains Agathe Euzen, deputy scientific director at the CNRS Ecology and Environment Institute.

It is obvious that an extreme event, such as a storm, which occurs in a territory which is not inhabited has much less consequences than in the territories occupied by human activities, dwellings, infrastructures … which tend to develop and are therefore more vulnerable.Agathe Euzento franceinfo

Therefore, heavy rains are not enough to cause flooding. Likewise, a heat wave or drought cannot be the only ones responsible for forest fires.

“By nature, a risk is unpredictable”, replies the climatologist Hervé Le Treut, president of AcclimaTerra, the regional committee on the climate in New Aquitaine. “On the other hand, we are able to determine which areas are exposed to which dangers. For example, where the water flows in a very narrow pass, it is water that can go very fast and be very violent. there is always an element of the unexpected, that’s the difficulty. “

Saint-Martin-Vésubie, a town partly destroyed by the bad weather of October 2, benefited from a “low” risk index. It was even “very weak” at Bollène-Vésubie, where the river washed away the road on which a car was traveling with two firefighters on board. Likewise, a phenomenon can affect one region one year and another the next, making it difficult for residents and local authorities to perceive this risk.

More intense and frequent events

The climatologists interviewed by franceinfo are categorical: the risks are increasing due to climate change, including on French territory, as evidenced by data from the Ministry of Ecological Transition. The January report indicates that the annual frequency ofaccidents very serious “which caused more than 10 victims and / or more than 30 million euros of damage – has almost quadrupled in 20 years: from one event per year between 1950 and 1996, we went to 3.6 over the period 1997- 2017. However, since the collection of these data, hurricanes Maria and Irma swept through the West Indies, the city of Cannes again found itself under water, France has experienced several scorching episodes (sometimes in the same summer), a flood of the Aude caused significant damage …

“All the territories will have to live with greater uncertainties than before”, abounds Antoine Nicault, écologist and paleoclimatologist, member of GREC-Sud, the regional group of experts on climate in the Provence-Alpes-Côte d’Azur region. In his region, the rise in the temperature of the Mediterranean coupled with the rise in the air temperature was able, with the presence of a southwest flow, to create the ideal conditions for the exceptional precipitation observed this autumn in the Cévennes and the Nice hinterland.

“We have a doubling of the frequency of events that exceed 200 mm of rain per day, the limit from which we speak of a Mediterranean episode. We also observe an increase in the intensity of these episodes of the order by 22% “, notes Antoine Nicault.

These events have always existed. Except that with climate change there is pressure on certain variables at the origin of these phenomena.Antoine Nicaultto franceinfo

Likewise, the rise in sea level increases erosion and the risk of submersion in the event of a storm, in New Aquitaine, near Hervé Le Treut.

“France is a very interesting observatory because we know both the problems of the countries of the Mediterranean basin and those of the countries of the North”, notes in turn the geographer Magali Reghezza-Zitt, member of the High Council on the climate. In a city, “We are observing a ‘Mediterraneanization’ of France with, for example, fires north of the Loire. That is new.”

Firefighters in the northern half of France have long sent forces over the summer to the south to fight the fires. From now on, they can be called upon to intervene on forest fires at home.Magali Reghezza-Zittto franceinfo

In March 2019, the National Conference on Natural Risks estimated that the forest fire season could lengthen from three to six months by 2050, now exposing the Pays de la Loire, Val-de-Loire and Brittany. Worrisome forecasts that put the question of adaptation on the table.

“We are not going to rebuild identically”, Emmanuel Macron warned Wednesday from the Vésubie valley. Some houses too close to the river will have to be evacuated and development work will have to be carried out, so as to limit the artificialization of the soil. Because the mistakes made in the past in terms of development pay dearly, according to the experts contacted by franceinfo. It is urgent to adapt, they warn, without forgetting to fight against climate change. Reducing greenhouse gas emissions is still the best way to reduce the risk of natural disasters.

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