Malpasset

Aerial view of the dam ruins in 1988

Coordinates: 43°30′43.48″N 6°45′23.40″E / 43.5120778°N 6.7565°E / 43.5120778; 6.7565

Malpasset was an arch dam on the Reyran River, constructed approximately 7 km north of Fréjus on the Côte d'Azur, southern France, in the Var département. It collapsed on December 2, 1959, killing 421 people in the resulting flood. Various sources indicate death numbers of 361, 400, 423, 429 or 510. The damage amounted to a total of $68 million.

Construction

The dam, which was a doubly curved equal angle arch type with variable radius, began construction in April 1952 and finished in 1954 to supply water and irrigation for the region. Delays due to lack of funding and labor strikes halted construction a few times. Another source reports that construction began as early as 1941. Construction cost 580 million francs (by 1955 prices), and was led by well-known French engineer André Coyne. The project was funded and owned by Var département. Concurrent with the dam construction, the A8 autoroute was also being built 200 meters away from the dam location.

Disaster

The dam was breached at 21:13 on December 2, 1959. The entire wall 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 metres (130 ft) high and moving at 70 kilometres (43 mi) per hour, destroying two small villages - Malpasset and Bozon, the highway construction site, and in 20 minutes reaching Fréjus, still standing 3 metres (10 ft) high. Various small roads and railroad tracks were destroyed as well, water flooding the western half of Fréjus and finally reaching the sea.

Cause

Geological and hydrologic studies were conducted in 1946 and the dam location was considered suitable. Due to lack of proper funding, however, the geological study of the region was not thorough. The lithology underlying the dam is a metamorphic rock called gneiss. This rock type is known to be relatively impermeable meaning that there is no significant groundwater flow within the rock unit, and it does not allow water to penetrate the ground. On the right side (looking down the river), was also rock, and a concrete wing wall was constructed to connect the wall to the ground.

Weeks before the breach, some cracking noises were observed, but they were not examined. It's hard to determine when the cracking noises started. The right side of the dam had some leaks in November 1959.

A tectonic fault was later found as the most likely cause of the disaster. The water collected under a wall, unable to escape through the rocks. The water pressure was aimed diagonally towards the dam wall, and was not found initially. According to a source, explosions during building of the highway might have caused shifting of the rock base of the dam.

Between November 19th and December 2nd, there was 50cm of rainfall, and 13cm in 24 hours before the breach. The water level in the dam was only 28cm away from the edge. Rain continued, and the dam guardian wanted to open the discharge valves, but the authorities refused, claiming the highway construction site was in danger by flooding water. 5 hours before the breach, at 18:00 hours, the water release valves were opened, but with a discharge rate of 40 m³/s, it was not enough to empty the dam in time.

Until the Malpasset incident, only 4 other incidents of arch-type dam breaches were recorded:

• Manitou dam, Manitou Springs, Colorado, 1924 at 38°52′35.47″N 104°59′38.30″W / 38.8765194°N 104.993972°W / 38.8765194; -104.993972 (Manitou dam))
• Moyie dam, Moyie Springs, Idaho, 1926 at 48°44′1.28″N 116°10′30.61″W / 48.7336889°N 116.1751694°W / 48.7336889; -116.1751694 (Moyie dam)), which is still in use, generating electricity.^[1]
• Lake Lanier, North Carolina, 1926
• Purisima dam, California, 1930

See also

• List of natural disasters by death toll - Floods and Landslides
• List of wars and disasters by death toll - Flood disasters
• Sarez Lake

References

1. ^ http://www.fwee.org/news/getStory?story=1297

• J. Bellier, Le barrage de Malpasset, 1967
• Max Herzog, Elementare Talsperrenstatik, 1998
• Max Herzog, Bautechnik 67 Heft 12, 1990
• Application of the Method of Characteristics to the Dam Break Wave Problem, Journal of Hydraulic Research, 47 1: 41-49 (DOI: 10.3826/jhr.2009.2865)

External links

• The Malpasset Catastrophe in 1959 French language article with images
• Cracking of dams
• Chanson, H. (2009) Application of the Method of Characteristics to the Dam Break Wave Problem Journal of Hydraulic Research, IAHR, Vol. 47, No. 1, pp. 41-49 (DOI: 10.3826/jhr.2009.2865) (ISSN 0022-1686)
• Website dedicated to the disaster of Malpasset