Malpasset Dam

The Malpasset Dam was an arch dam (convex surface facing upstream) on the Reyran River, north of Fréjus on the French Riviera. It collapsed on 2 December 1959, killing 423 people in the resulting flood. The breach was caused by a tectonic fault in the impermeable rock base, which had been inadequately surveyed. Nearby road-building works, using explosives, may also have contributed to the disaster. The structure was a doubly curved, equal-angle, arch-type dam with variable radius. It was built to supply drinking and irrigation water for the region. Construction began in April 1952 and was finished in 1954. Another source reported that construction began as early as 1941. Delays due to lack of funding and labor strikes interrupted construction a few times. The project was led by well-known French engineer André Coyne. Construction cost 580 million francs (by 1955 prices), and was funded and owned by Var département. Concurrent with the dam construction, the A8 autoroute was also being built further down the course of the Reyran from the dam location. The dam was supposed to regulate the rate-of-flow of the river that it was near and to store 50 million cubic metres of water for agricultural and domestic use and for the tourism sector of the area. The dam was in width and high, and had a thickness of at the base and at the rim. Signs of an imminent collapse began in November 1959; a "trickle of clear water [was] observed high on the right [side]" and then cracks were noticed later in the month in the concrete apron at the dam toe. The dam was breached at 21:13 on December 2, 1959. The break was partially due to rainfall and thus the rising level of water; by noon on 2 December 1959, the reservoir had reached its maximum level. The guardian André Ferro asked for permission to release the excess water and was denied the ability to do so until 18:00 of that day. By then, the amount of water was so high that it took three hours to release only a few centimetres of water. The entire wall then collapsed with only a few blocks remaining on the right bank.