At the end of the 1939-45 war, one of the many problems that the Var Conseil Générale had to solve concerned water. The greatest need was in the south of the department, a region experiencing fast growth in tourism and agriculture – the fruit and vegetables from Fréjus already enjoyed an international reputation.
The Ministry of Agriculture, in a decision on 3 August 1950, agreed to build a dam on the Reyran river on the Malpasset site.
Malpasset means bad passage, a place where travellers and merchants were attacked by highwaymen. Reyran in Provençal comes from “Riaio” (torrent) and “Ran” (abundance). The valley is dry three quarters of the year, but when the rains came it could cause serious flooding on the Fréjus plain.
Taming the Reyran was therefore important. The water reservoir that would be created, would bring essential water to the ever-increasing population, water the thirsty land, help develop the tourism and protect the Esterel forests from fire. The dam was the work of the Var Conseil Générale. Professor Corroy of the Faculty of Sciences in Marseille was consulted and gave a favourable preliminary geological report on the locality: Malpasset.
The firm of André Coyne, president of the Association Internationale des Grands Barrages was approached by Conseil Générale to conduct the preliminary study on the dam project. He was the most famous of the engineers specializing in vault dams. His greatest achievements included Tignes and Bort-les-Orgues in France and the dam on Lake Kariba in Zambia, one of the largest dams in the world.
The type of dam chosen was an arch dam. The arch on the dam is designed so that the force of the water against it presses against the arch, compressing and strengthening the structure as it pushes into its foundation or abutments. This type of work means the banks receiving the bulk of the pressure have to resist any test. On the left bank the lack of a shoulder to serve as a stop meant an artificial abutment in reinforced concrete had to be built.
Construction started on 1 April 1952 and was completed in 1954. Characteristics of the dam:
Maximum height – 59 m
Cap – 225 m
Total holding capacity – 49,300,000 m3
Wall thickness: base 6.78 m, top 1.50 m, which made it the thinnest dam in Europe.
In autumn 1959, torrential rain fell in the region for three weeks.
There is no possible means of controlling the first filling of the dam, the most critical phase in its life. Filling began at the end of 1954, but due to delays in expropriations the reservoir had not exceeded 95%.
At 6:00 pm on 2 December 1959, the order was given to open the drain valve.
The consequences were dramatic. There were officially 423 dead, 7,000 victims, 79 orphans. In 1970 the damage amounted to more than 100 million francs.
Malpasset, built for the glory and wealth of the region unfortunately brought disaster and despair in its wake. The “Pink Valley had gone forever”.
It took 8 years for the causes of the disaster to be clearly established and recognized:
In the ruling delivered by the Court of Cassation on 7 December 1967:
“No fault, at any stage, has been committed”
The expulsion of the rocky dihedron on which the foundations of the left bank vault abutment sat appeared to be the cause of the dam breaking. The Malpasset accident led to the technical regulations being strengthened with in 1967 the establishment of a Permanent Technical Committee for Dams.