Deadly floods of November 1999: in Aude, how new technologies contribute to informing the general public about flood risk

“In 1999, we estimated the rain that fell using rain gauges“, recalls Florence Vaysse, from Météo France. A symbol of the passing of time, and the opportunity to recall that the organization takes full advantage of progress in science and new technologies to improve its forecasting capabilities: “Today, water mark readings, with constantly recalibrated calculations, are valuable tools for forecasters. Many things have changed, thanks to new tools: we are installing more and more radars, particularly in mountainous areas, we have been increasing the number of measurements, benefiting from the contribution of satellites, since the 2000s.”

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Progress also made available to the general public: “We must also not forget mobile phones: the Météo France app, for example, allows you to be notified as soon as the forecaster launches a vigilance, even before the prefecture fulfills its alert role by broadcasting it. is a tool that can be used anytime, anywhere, even on vacation, since you can locate yourself. I will also mention the Heavy Rain Warning at the municipal level (APIC): it is also. an important tool, which, by subscription, allows prefectures, town halls, intercommunities and operators to follow the evolution and location of the rainy episode or current floods (with Vigicrues Flash, on the same platform) to know the number of affected municipalities, and therefore to implement prevention and safety measures.

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Significant progress in the calibration of falling rain via a tool for merging radar data and rainfall measurements

And if, in September 2022, targeted communications for mayors were carried out in Aude to encourage these APICs subscriptions, Florence Vaysse recalls that “the general public can also have access to a simplified version”. If, since 1999, big steps have been taken, Florence Vaysse also specifies that post-October 2018 has brought its share of progress. Recently requested by the Aude prefecture to summarize the developments and new tools available for six years, the territorial referent provides a list of the improvements identified, citing “significant progress in the calibration of rain falling via a tool for merging radar data and rainfall measurements (Antilope)”. Enough to allow municipalities “eligible for heavy rain warnings” to benefit from calculated water levels “every 15 minutes”.

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A modeling finesse which should also soon concern Arome, one of Météo France's numerical forecast models, for which the passage from a grid of 1.3 km to 500 meters is “currently being tested by forecasters (France Weather) from the southeast”. So many materializations of the benefits of new technologies, hoping to make the best of what can sometimes combine the worst: Météo France is thus banking on social network monitoring tools for a “better real-time data tracking”.