how France has learned the lessons (but not all) of past disasters – L’Express

Waves of around six to eight meters on the Channel coasts, and eight to ten meters on the Atlantic should accompany these violent winds. The Basque Country is also affected, to the extent that gusts are expected “which risk exceeding 100 km/h on the coasts, a little less inland” and “an offshore swell between seven and nine meters”, as explained it at France Bleu Thomas Beauquesne, forecaster for Météo France. Six departments are also placed on yellow “rain flood” vigilance while thirteen others are also placed on yellow alert for flood risks, in the west and east of France.

Storm Ciaran should be less intense than the destructive winds of storms Lothar and Martin which shook France in December 1999: only “10 to 15%” of the territory should be affected by the disturbance. For comparison, storm Lothar “affected 56% of the territory with winds above 100 km/h and sometimes peaks at 160 km/h”, Lauriane Batté recalled this Tuesday during a press briefing, climatologist at Météo-France. Meteorologists and prefectures, however, are calling for caution: extreme phenomena are expected between Wednesday and Thursday. While lessons have been learned from previous large-scale disruptions, not all have yet been applied.

Progress has nevertheless been made since the trauma of 1999 and its “storm of the century”. At the time, Météo France had well predicted Lothar and Martin. Three days before their passage, the situation concerned forecasters enough for them to issue an alert bulletin intended in particular for Civil Security. But these precautions are not enough: gusts of winds cross Finistère, Brittany, Alsace and the Germany region, causing a heavy human toll. In France, 140 deaths have been reported. This episode generates a double awareness.

First, the need to better inform the general public about the precautions to take. “It was following the 1999 storm that the meteorological vigilance system was created,” explained Olivier Caumont, director of operations for forecasting at Météo France, during a press briefing on Tuesday. The first vigilance card with four levels (green, yellow, orange, red) to mark the level of risk was presented on October 1, 2001. Each color corresponds to different precautions for the departments concerned. These maps are enriched over the years and disasters: the risks of extreme cold or heatwaves were, for example, added after the summer of 2003 and its 71,000 deaths. In 2007, the “heavy precipitation” alert became “rain flooding”. In 2010, after the Xynthia storm, the map included the “waves-submersion” alert. This relay of information seems to have reached the public: according to a study carried out by the BVA institute and taken up by Météo France93% of French people surveyed said they were aware of the vigilance card in 2021.

Forecasting capabilities would also improve. “We are now able to make very high quality forecasts, which have considerably improved compared to the phenomenon we saw in 1999,” explains Robert Vautard, research director at the CNRS and co-chair of the working group. 1 of the Intergovernmental Panel on Climate Change (IPCC). At the time, we were less efficient in the quality of observations, but also in the resolution of the models, which gave less precise forecasts than today. hui.” The increased quality of technical equipment (whether satellites, radars or simulators) has enabled meteorologists to be more efficient. In his Vigilance report 2022, Météo-France indicates that “in nearly 9 out of 10 episodes, the dangerous meteorological phenomenon occurred in the department with the intensity and expected consequences”. In 2019, the organization indicated daily Release that risks were now detectable a day and a half earlier than they were twenty years earlier.

Since storms combine many variables, they remain difficult to predict. In October 2020, the ravages of storm Alex, which devastated the Roya valley, in the Alpes-Maritimes, were surprising, leading to ten deaths, eight missing and several hundred million euros of infrastructure destroyed. The deluge caused devastating floods in the Nice hinterland, cutting off around 13,000 inhabitants from the world. “We are today able to predict Alex-type storms, but we always remain surprised by the intensity of the trajectories of these winds,” says Pascal Yiou, researcher at the climate and environmental sciences laboratory, attached to the CNRS. and specialized in mathematics applied to climate. We are in the case of an explosive storm, which, instead of dying gently inland, strengthened by veering towards abnormally warm Mediterranean waters at this period of the ‘year”. Unlike temperatures, the frequency of storms does not seem to be affected by climate change. Their intensity, on the other hand, seems to be increasing. In its sixth report, the IPCC confirmed that episodes of heavy precipitation would intensify if global warming exceeds 2°C.

Failing to be able to prevent these phenomena, the authorities are therefore trying to limit their impact. After storm Alex, the public authorities had to develop crisis governance involving elected officials from the Nice metropolis and the prefecture, in order to better coordinate the safety of residents, the management of compensation procedures and the rehabilitation of infrastructure. With relative success. Three years after the storm, the precautionary principle seems to have been integrated. Before depression Aline passed last week, 760 firefighters from the department were pre-positioned to intervene, as well as 530 police officers. Public transport was interrupted in the valleys and shopping centers of more than 5,000 square meters were closed on Friday morning. But, on the infrastructure side, the results are much more mixed: the town of Saint-Martin-Vésubie, particularly affected by the storm, has not completed its reconstruction. Its cemetery, washed away by torrential rains, has still not been rehabilitated.

Beyond the particular case of the Roya valley, the question of infrastructure also arose after the devastation of storm Xynthia in February 2010. The phenomenon caused 47 deaths in France, including 29 at the seaside resort of Faute-sur-Mer, raising the question of coastal construction and development. “Today there are more than 200,000 people residing in low-lying areas, less than a kilometer from the coast, where the risks of marine submersion are greatest,” noted the researchers François Gérard and Michel Lang in an article published in 2020 in the International Water Reviewadding that the Atlantic coast had experienced strong urbanization “without real consideration of the risk of marine submersion, which led to a very significant increase in the stakes exposed and poor preparation in the event of submersion”.

Where 50 years ago, yesterday’s storms and floods only affected the entrance to a fishing village of a few dozen people, today’s storms are hitting towns with several thousand inhabitants, increasingly more advanced towards the sea. To reduce the risk, public authorities often try to provide a technical response, in particular through the construction of dikes. After Xynthia, the State released 22 million euros for that of Calais. In Dunkirk, the public authorities preferred to resilt the beach to protect the sea wall.

“But these structures, very effective in the face of average weather phenomena, risk failing in the face of the intensification of storms and floods,” notes Bruno Barroca, director of the Ville-Transports-Territoires doctoral school at the University of Paris. Est, who describes them as “maladaptation”. Today, on the Bay of Lancieux side, in Brittany, the various dykes erected since the 14th century are sometimes rendered ineffective by the rising tide, creating surprise floods. “The construction of the permanent dike is often the only response to rising water levels, deplores Bruno Barroca. Faced with the intensification of future phenomena, we will have no choice, we will have to think of other solutions , which notably involve a withdrawal of populations from certain areas of the coastline.”