Loire-Atlantique in red vigilance: what does this maximum alert level correspond to? – LCI

After the Gard in mid-September, Météo-France placed Loire-Atlantique on red “rain-flood” vigilance this Saturday, from 8 pm to 6 am, due to a “episode of long-lasting and sustained rains” to “exceptional character”. This is the first time that this department has been subjected to such a level of alert. 80 to 100 mm of rain are expected on “the central half of the department and could locally reach 110 mm”, specifies the meteorological institute while 22 departments are also in orange vigilance. It’s a little over a month of rain that could fall in about fifteen hours …

This type of classification remains rare on the part of Météo France, which set up this vigilance mechanism in 2001, after the storms of 1999.

Last month, the Gard had suffered a historic Cevennes phenomenon in its intensity, bringing to 26, the number of times it was triggered for rain-flooding, including ten due to heavy rainfall. In 2020, it had been issued three times between May and October. But what does this alert threshold, the fourth and last on the scale used, actually mean? Red vigilance is declared when “an episode of long-lasting and sustained rains requires particular vigilance because of its exceptional nature”, indicates Météo-France in its bulletin.

During this time, “Absolute vigilance is required. Dangerous phenomena of exceptional intensity are expected“, indicates Météo-France on its site, also calling “to absolutely respect the safety instructions issued by the public authorities”.

The meteorological institute then draws up a list of possible consequences, including “Very significant floods are possible, including in areas that are rarely subject to flooding, in all the hydrological basins of the departments concerned”. “Road traffic conditions can be made extremely difficult throughout the network”, indicates Météo-France, citing risks “overflow of sewerage networks” and “more or less long power cuts may occur”.

At each red alert, the Ministry of the Interior publishes via Twitter, in particular a list of instructions to be followed: among the recommendations for caution, it is asked to stay upstairs and not to go down into the basements, but also not to go downstairs. under no circumstances, on foot or by car, on a submerged path. In addition to informing citizens, vigilance is also intended for civil security services and health authorities, who can thus alert and mobilize, respectively, intervention teams, professionals and health structures.