A bit a recent history of the region includes the disaster of the Malpasset dam (barrage de Malpasset), which broke on the night of 2 December 1959 and killed over 420 people, possibly even more than 500. On the map, the blue area above the dam was the "lake" area created by the dam. (The southern edge of the current Lac St Cassien is at the top edge of our map.) The blue area below the dam shows the area flooded when the dam broke.
"Malpasset" translates roughly to "passes badly" or "doesn't go very well". Although that turned out to be an appropriate name for the ill-fated dam, the area was really named after a local version of Robin Hood, one Gaspard de Besse who attacked all the passing stage coaches (diligences). He was said to take from the rich and give to the poor, although the rich could have been anyone with something worth stealing.
The Reyran river runs south about 15 km through the hills to Fréjus where it empties into the Mediterranean along with the Argens river. The Reyran is a mercurial river, completely dry during the hot summer months and a raging torrent in the winter and spring.
To tame the river and provide year-round agricultural water to the region, it was decided to build a dam in the valley about half way between Lac St Cassien (not yet a lake) and Fréjus. Geological studies were done in 1946, but even then there was some disagreement about the suitability of the land.
André Coyne was selected to build an arched dam (barrage-voûte) across the valley. He had already built similar dams in India, Marocco, Rhodesia and at Tignes and Bort-les-Orgues in France. An arched dam is arched in the upstream direction and isn't completely rigid, so the pressure of the water actually distorts the dam and forces the dam more tightly against the sides. This type of dam is extremely reliable, as long as the terrain at the sides and bottom is very solid.
From the round-about by the Fréjus autoroute exit, follow the signs for "Malpasset", along the small D37 road, about 4 km. There's a first parking area, for walking/hiking in the natural park; the road becomes dirt-gravel, crosses the stream at a ford and goes about 500 m to pass under the autoroute and arrive at the "barrage" parking.
The hills here seem low and tame today, sitting along side the autoroute A7 as it passes near Fréjus. Walking up from the parking area you pass a pretty and calm little river [photo-1], and when you see the dam you realize how big it really was. It stood about 60 m high and arched about 400 m across the valley.
On the right bank of the river (your left as you go up the valley), enough of the dam remains [photo-3] to give you a good idea of its size and shape, with the broken cement wall stepping down towards the bottom. The opposite side of the dam was completely torn away from the banks. The extreme end of the dam, with its iron railing still visible, sits at the top [photo-5], and one huge segment lays "head-down" on the hillside [photo-6].
Walking back down the stream, after seeing the dam, you'll be more aware of the huge cement blocks, weighing hundreds of tons, that washed kilometers downstream in the raging flood waters.
A number of factors that probably contributed to the disaster seem obvious today. The geological condition of the rock was either not understood or not appreciated. Anthracite (hard coal) was then being mined at Boson just 4 km below the dam site. The thin coal deposits were mixed with gray schists and shale, and with large areas of soft white flourite. The different types of rock had incompatible qualities, especially for a region with such weather extremes. In the summer, both the complete dryness and the constant sun baked the ground, with different rock reacting differently. In the winter, torrential rains pounded the area, and some of the rock absorbed the water. Because of under funding, the geological study of the rock was not thorough enough.
The dam took 30 months (two and a half years) to build -- the Empire State building took just over a year. Started on April-fools day in 1952, the construction halted several times because of lack of funding and labor disputes, leaving long periods for parts of the cement to harden completely before work resumed and new cement was added. This could have resulted in a non-homogeneous structure.
Following the construction of the dam, the A8 autoroute was being built across the hills only 200 meters away. Local lore has it that the explosions ocurring to build the autoroute shifted the earth and rock at the dam. This could have loosened the critical attachment of the dam to the shoulders of the rock, precipitating the failure. The explosions could also have shifted the concrete within the dam itself, opening hollows or unseen cracks.
The dam was completed in December 1954, and gradually filled up over the next five years. With the autumn rains of November 1959, the water was still 7 meters below the top when small leaks were discovered along the right bank of the dam. The leaks grew rapidly, indicating a serious danger, but the population was not notified.
A tidal wave hit the Mediterranean coast on the 2nd of December, making the population nervous and expecting another tidal wave even while the rains were coming down. There was nearly 50 cm of rainfall from the 19th of November to the 2nd of December, with 13 cm in the last 24 hours.
And the dam filled for the first time, to the brim and overflowing. The guardian of the dam set out on his mobylette to warn the authorities, the phones not working because of a telephone-company strike. He wanted to open the valves to release some of the water pressure but, to prevent damage to the new bridge pylons being built for the autoroute, permission was refused.
The First Wave
Following more inspections in the afternoon, the valve was finally opened at 18h00 and the water level began dropping a few centimeters. It was too-little too-late. At 21h13, while the guardian of the dam was at home with his wife and 3-year-old son 2 km down-stream, the dam burst and a 40-m high wall of water came down the valley at 70 km an hour.
Below the Dam
Immediately below the dam were a couple of isolated houses, the hamlet of Malpasset, the Bozon mining hamlet and the autoroute construction site. When the dam burst, the mass of water tore through here along with much of the dam itself, carrying 600-ton blocks of cement as far as 1.7 km downstream and destroying and killing all in its path. Most of the residents here died, including all the Malpasset hamlet and the construction workers; it's thought that there may have been as many as 100 unregistered workers who perished, undiscovered or unidentified in the final count.
The waters roared down the valley, spreading out as they hit the plains at the mouth of the Argens and flooding across the western half of Fréjus and into the sea. The western part of the town, including the Roman amphitheater, was completely flooded, as was the southern part of town, including the rue Henri Vadon and Ave de Verdon, along with the railway station and the entire coastline.
Kilometers of railway line were torn out and twisted and the land was devastated. Roads were destroyed completely and many hundreds of houses, farms and factories were wiped out. The cost of lost lives was enormous, with entire families being eliminated and others suffering the pain of lost relatives. Many were washed out to sea and some found a week later 60 km away at Port-Cros. An unknown number of others were never found.
Keeping the valves closed during the day didn't save the fresh cement of the autoroute pylons after all. The entire section of the new autoroute was ripped away and the precious pylons were broken and scattered through the hills like toys.
A two-thousand year old Roman aqueduct followed the hills along the east side of the dam, and the vestiges can be seen there today. One pretty section crosses a small valley only about 700 meters below the dam, on the east side of the autoroute [photo-7]. A sign of a much sturdier construction or the luck of the location?
IGN (1/25,000) #3544 ET "Fréjus, St-Raphaël, Corniche Esterel"
Didier Richard (1/50,000) #26 "Pay d'Azur"
Didier Richard (1/50,000) #25 "Maures Haut-Pays Varois"
• Latitude, Longitude: 43.640815, 7.008553