After the high summer heat, the arrival of autumn is particularly risky this year. Meteorologists and communities have been on alert for several weeks.
Red alert. Météo-France had placed Gard and Hérault in absolute vigilance at the start of the evening this Tuesday, due to “stationary thunderstorms» and exceptional rainfall volumes. In the two southern departments, where crisis units have been activated, “stationary thunderstorms are well established» et «the exceptional intensity of the precipitation observed requires a passage in red vigilance“, had announced the meteorological service. Before returning to an orange alert for these two departments in the middle of the evening.
The storm that devastated Corsica in August heralded the start of the stormy season which affects south-eastern France and the Mediterranean region every year. And 2022 could be a historic vintage according to meteorologists, due to the exceptionally high temperatures of the sea and the soil. “The Mediterranean Sea temperature anomalies observed this summer are one of the factors that could aggravate the intensity of these Mediterranean rainfall phenomena this year.“, warns the Ministry of Ecological Transition. The government has also launched an awareness campaignin the 15 departments around the Mediterranean on the risks of Mediterranean phenomena».
This threat, the municipalities of the region have become accustomed to living with. “We are already on the block every year“, we underlined at the end of August at the town hall of Saint-Laurent-du-Var. Same tone in Vaison-la-Romaine: “There is a relative fear“, detailed Jean-François Périlhou, the various right mayor. Admittedly, the scorching summer called for caution, but this elected official preferred to highlight the force of habit and the high degree of preparation of the region in the face of these annual episodes. “We are broken, it’s cultural“explained the bravado elected.
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As every year at this time, the waterways have been cleaned to remove obstacles to the proper flow of water and exercises are held regularly. But no major work has been specifically planned. “An arrangement is a long time», justifies Eric Ménassi, PS mayor of Trèbes, in Aude. “We need preliminary studies, co-financing because the municipalities cannot support them alone…».
The long development time
His city was seriously affected in 2018, six people had died, “an indelible trauma“. Since then, 600,000 euros have first been invested in channeling runoff water in the north of the city. In the south, 52 houses were preempted by the State and destroyed because they were in a dangerous zone. But it is only at the end of this year that a broader work of redevelopment of the riverbed will begin. “It is necessary to lateralize the watercourse, the dykes are not a solution because they accelerate the speed of the watercourse“explained the city councilor.
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These major works, planned over several years, are detailed in the PAPI (Flood Prevention Action Program). That of Ouvèze was thus spread out from 2017 to 2023 and provided for 27 measures for a total of 6 million euros.
Vital precautions but not always sufficient. In case of danger, the municipality knows how to react quickly: “We have water measurements 30 minutes and one hour upstream, explained the mayor of Vaison-la-Romainein case of too high a rise I can launch an automatic call to 200, 300 or more people for an emergency evacuation». «At constant flow (those of 1992 Editor’s note), the human and material consequences will be lower“, he felt confident, but”with the river, there are no limits».
Inevitable epiphenomena
What to head for a disaster foreshadowed? Not necessarily, tempered Régis Crépet: “Certainly the heat of the soil and water is the driving force behind such extreme phenomena, but they do not automatically guarantee them.“. Indeed, a trigger is needed to cause the creation of climatic instability: the arrival of a mass of cold air. It is the encounter with the lower heat that causes a breakup and the creation of clouds.
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Not enough to reassure the mayors concerned, such as that of Vaison-la-Romaine where 30 years ago, the floods had led to the death of 38 people, plus 4 missing. “According to the ancients, he underlined”in 1992 not a drop of water fell during the summer, just like this year».
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