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^{[citation needed]}. 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 1,400 m (1,500 yd; 0.76 nmi) 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 222 m (728 ft) in width and 66 m (217 ft) high, and had a thickness of 6.78 m (22.2 ft) at the base and 1.5 m (4 ft 11 in) 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 2 December 1959. The break was partially due to rainfall and thus the rising level of water; by noon on 2 December, 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. Pieces of the dam are still scattered throughout the area.

The breach created a massive dam-break wave, or wall of water, 40 m (44 yd; 130 ft) high and moving at 70 km/h (38 kn; 43 mph), destroying two small villages, Malpasset and Bozon, the highway construction site, and in 20 minutes, still standing 3 m (3.3 yd; 9.8 ft) high, reaching Fréjus. The water was recorded traveling at speeds up to 70 km/h (38 kn; 43 mph) with large chunks of the concrete wall some weighing up to 600 tonnes (590 long tons; 660 short tons). Various small roads and railroad tracks were also destroyed, with water flooding the western half of Fréjus and finally reaching the sea.

The death toll of the dam breach was reported as 423, with 135 children under the age of 15, 15 minors between 15 and 21 years old, 134 men, 112 women, and 27 individuals who were never identified. Additionally, 79 children were orphaned and 83 people were injured. Other damage included 155 buildings destroyed, 796 buildings damaged, and 1,350 hectares (3,300 acres) destroyed, the amount of destruction totaling about 425 million euros in 2010 terms. The damage amounted to an equivalent total of US$68 million. The event also ushered in the practice of posthumous marriage in France for civilians, as many women who lost their fiancés were granted the right to marry them after death.

Some 1959 postage stamps had a flood surcharge imprinted on them, to raise money for flood victims.