Episodes of heavy rain in autumn are one of the characteristics of the Mediterranean climate. That of this October 17, 2024 surprised by its intensity, which ranks it among the most important of the last twenty years. Here are the notable episodes, the most recent recorded by the Weather Channel.
High annual variability
THE Cévennes episodes et Mediterraneans are likely to occur every year, especially between September and November. Some years are less active than others, a bit like hurricane seasons. On average, one year out of two is active in France, and very significant episodes occur once every three years. Sometimes, several years follow each other with strong activity. Since the beginning of the 2000s, we have identified a group of active years between 2000 to 2005, then between 2008 and 2011. The year 2014 was also intense. Then, the episodes lost intensity and geographical area.
– September 2020: this is the latest violent episode to date. Although brief and not extensive, this episode caused torrential rains in the Cévennes with up to 550 mm in 24 hours in Valleraugue (Gard). There were two victims swept away by the waters.
– September 2014 was marked by an intense, but brief episode on the Hérault, up to Montpellier, flooded, with 300 mm, causing a flash flood of the Lez.
– November 2011: a large-scale Mediterranean episode occurred in the first decade, lasting and very widespread from the Cévennes to PACA. This episode presented values higher than those recorded on October 17: up to 936 mm in Valleraugue (30) and 642 mm in Villefort (48). The Hérault river experienced a major flood.
– End of October and beginning of November 2008: a situation quite similar to the one we have just experienced occurred in the Cévennes, with accumulations reaching 428 mm in Villefort (48). There too, the watercourses descending from Haute-Loire experienced a major flood, exceeded this time, at Rive-de-Gier. The Loire River experienced a major flood which is still a reference.
– September 2002: a major disaster with the floods of Sommières (Gard). A particularly intense Cévennes episode hit Gard and part of Hérault. In 24 hours, it fell to 543 mm in Saint-Christol-les-Alès (30) and even 687 mm over the entire episode in Anduze (30).
These are episodes that have occurred in this geographic area since the 2000s. In the past, major disasters, sometimes much worse than these, have occurred, with for example 30 victims in Gard in September 1958 following torrential rains. The archives also show us catastrophic and deadly floods in the 19th century, such as in September 1890 when 971 mm fell in 5 days in Montpezat (Ardèche), causing 50 victims. We can think that territorial planning measures and especially prevention measures (alerts, social networks) nowadays favor mobilization and caution, thus limiting the number of victims.
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