The peak of the Garonne flood in Gironde was reached Thursday morning in La Réole, at 8.43 meters. “Since Thursday 8 am, her level has fallen, and by 6 pm she will be fully back in her bed” announces the mayor of La Réole Bruno Marty (PS).
We are therefore far from the 10.60 meters announced on Tuesday by the Vigicrues site. An error of appreciation which today makes the elected official jump. “This announcement created a wave of panic and many evacuated, transferred furniture to the floors … We saw clearly on the ground, and in particular with regard to the situation in Tonneins (Lot-et-Garonne), that this was not possible ”fulminates Bruno Marty.
Human error and technical bug
A flood at 10.60 meters would indeed have created immense damage, and certainly required the evacuation of many homes. Pierre-Paul Gabrielli, responsible for the natural and hydraulic risks of the Dreal (Regional Directorate for the Environment, Planning and Housing) who oversees Vigicrues, recognizes the error. “We produce at least two daily bulletins, at 10 am and 4 pm,” he explains. Tuesday morning, perhaps under the effect of fatigue, because the agents have been very mobilized for several days due to the situation in the Pyrénées-Atlantiques, the Landes, Les Hautes-Pyrénées and the Gers, there was a human error, first on the height, since instead of displaying 8.70 m we displayed between 10 m and 10.60 m, then on the temporality, since instead of announcing that the peak had to intervene Thursday morning, it was indicated Wednesday. “
That’s not all. “We quickly realized our error, but the update was not done, due to a server bug,” continues Pierre-Paul Gabrielli. So the correction did not appear until the 4 p.m. bulletin. “In the meantime,” the phones have exploded, assures Bruno Marty, even if I immediately reassured my constituents by saying that it was undoubtedly an error. “We understand the anger of the mayors who found themselves arrested” slips the head of Dreal.
“These are the mayors who had to deal with the wind of panic”
The mayor of La Réole admits for his part that “error is human. “” We could be wrong, but it would still be time to ask the mayors during these episodes of flooding, because there we were not even kept informed, while we are on the ground, and that the we know how the river works. The Garonne rarely rises more than 20 cm per hour, we have time to discuss, and to validate or not the forecasts. There, it was balanced on the site, and behind it is the mayors who had to manage the wind of panic. “
Bruno Marty also recalls that “Vigicrues was already wrong in 2019, by making an announcement at 10.40 m when we had reached 8.90 m, and in 2021 it was the opposite, they had largely underestimated the flood episode, even though I had warned about the danger. “
Flood phenomena “will become more and more recurrent”
La Dreal recalls that these forecasts are drawn up “with precipitation data from Météo France, and flow propagation calculations that are transformed into height. “Pierre-Paul Gabrielli evokes” bad luck “for this episode, but ensures that” in general the system works. “” We make forecasts seven days a week, 365 days a year, and in the vast majority of cases our forecasts are good, even though, unfortunately, there are more and more flood events. “
Vigicrues thus finds himself more and more exposed. “For three years, we have had one flood every winter, or even two or three, while statistically there is a one in ten chance per year of suffering from it,” analyzes Yann Lacaze, head of the Vigicrues department for the Gironde, Adour and La Dordogne. We can imagine that we are therefore in the trend announced by the IPCC of a strengthening of extreme phenomena, even if for the moment we are only in a short time. “
Concretely, “this leads to increased demands on the part of users, which is normal, continues Yann Lacaze, and we are working to develop new tools, with artificial intelligence, to better anticipate these phenomena which, we fear. , will become more and more recurrent. We must also prepare for events that we have not yet experienced. We are not immune to encountering an upcoming event that exceeds anything that we have recorded.
In Tartas in the Landes, last winter we experienced the strongest flood recorded since 1852. ”
Start of the city clean-up
While waiting for the improvement of the systems, the Dreal recognizes that it “must progress in terms of communication”. “And we are obviously listening to elected officials, adds Yann Lacaze, in particular to get feedback from the field on the consequences of the events. This is valuable for integrating these elements into the models and maps that can later be used for crisis management. “
For his part, the mayor of La Réole mobilized on Thursday around twenty agents and elected officials, to begin cleaning the city’s docks and the interiors of the houses. Because at 8.43 m, the Garonne will still leave traces before slowly withdrawing.