While 2020 will be remembered by the whole of humanity for the global Covid-19 epidemic, it is also rooted in the memories of many people in the Mediterranean Arc due to four successive weather events that marked this extraordinary year. In January, Storm Gloria struck, while in June, sudden floods hit some parts of Ajaccio (see p.86). In September, rivers at the foot of Mont Aigoual caused major flooding and in October, heavy rains from Storm Alex triggered flash floods in the hills behind Nice.
Storm Gloria flew in on 22 January 2020 and battered the coastlines of Occitanie, PACA and Corsica.
Apart from the gusts of wind that caused direct damage it also triggered storm surges and sizeable wave trains that can flood coastal areas.
Coasts are honeypots of human activity where tourism infrastructure or holiday complexes and are especially vulnerable.
Ever since Storm Xynthia and the Faute sur Mer disaster, in the Vendée, on 27 and 28 February 2010, coastal flooding has risen up the public authority agenda, in terms of land management.
Seafront homes at Racou Beach,
Argelès-sur-Mer (66), once again
overcome by the waves and sea foam.
Torrential rain in the Cevennes
On 19 September, unusually heavy rain fell on an area below Mont Aigoual. Valleraugue (30) topped the charts with 720 mm of rain in 24 hours, 360 mm of which fell in just 3 hours. While it is noteworthy, this cumulative rainfall record falls short of even higher figure recorded in the same area in 1900, when 950 mm fell in 10 hours.
The biggest floods were in the upper catchments of the Hérault and Gardon de St Jean rivers. They caused huge damage to roads and two people lost their lives
Exceptional flooding in the Alpes Maritimes
On 2 October, while Storm Alex battered Western Europe, heavy rain fell on the foot slopes of the Mercantour mountains, behind Nice. The highest cumulative rainfall recorded was 500 mm in 24 hours, at St Martin Vésubie.
Two tributaries of the Var River (the Tinée and the Vésubie) and a coastal river (la Roya) became gorged with water and caused unprecedented levels of destruction. In this rugged landscape, the rivers burst or eroded their banks, damaging or completely destroying more than 1,600 homes and over 35 km of roads. Eight bridges were washed away, while in places, the rivers totally reshaped their floodplains.
One month later, eight people were confirmed dead while eleven were still missing.
The Vésubie River caused huge damage at St Martin de Vésubie (where the Madonne and Boréon meet to form the river), Roquebilière, Lantosque and St Jean la Rivière.
The height and speed of the water rose sharply where the river passes through narrow, rocky gorges while elsewhere, it severely eroded the soft rock riverbanks formed by ancient glacial moraine deposits. In places, the riverbank scouring washed away several dozen metres of land, uprooting everything in its path and sweeping it away. Here, at St Martin Vésubie, floodwaters from the Boréon River sliced through a house from the inter-war period, while another came within a few metres of suffering the same fate.
Meanwhile, the Roya wrought havoc on Tende, St Dalmas de Tende, Fontan, Breil sur Roya and all the way the sea at Ventimiglia.
As with the Vésubie River, the whole area, which is connected to the coast by a narrow road corridor was completely cut off. Only a constant stream of helicopters and the intact railway line, built on an embankment, provided a link to the outside world for some weeks.
At Breil sur Roya, muddy floodwaters from the river buried these cars parked alongside the church in the Place Biancheri.
Photo: Florent Adamo – CEREMA*
As with areas further down the valley, Tende saw bridges and sections of the RD 6204 road that links the town to the coast, washed away.
Photo: Florent Adamo – CEREMA*