Vajont Dam is a dam completed in 1961 under Monte Toc, 100 km north of Venice, Italy. It was one of the highest dams in the world measuring 262 metres (860 ft) high, 27 metres (89 ft) thick at the base and 3.4 metres (11 ft) at the top.
Construction of the Vajont Dam
The management of SADE (Società Adriatica di Elettricità
), the company building the dam, told the public that the geology
of the gorge
had been studied, including analysis of ancient landslides, and that it was believed to be sufficiently stable. However, shifts in the rock were noticed during filling and there had been a lesser landslide of under a million cubic meters on November 4, 1960. As a result the water level behind the dam was lowered and the reservoir allowed to refill under controlled monitoring. Thus the reservoir was filled and slowly emptied three times, with movement of the ground being monitored and assessed to determine the dam's safety and to attempt controlled slippage of the potential landslide mass.
Landslide and megatsunami
On October 9, 1963 at approximately 10:35pm, the combination of the third drawing-down of the reservoir and heavy rains triggered an enormous landslide
of about 260 million cubic metres of forest, earth, and rock, which fell into the reservoir at up to 110 km per hour (68 mph). The resulting displacement of water caused 50 million cubic metres of water to overtop the dam in a 250-metre high wave, or megatsunami
. Despite this, the dam's structure was largely undamaged — the top metre
or so of masonry
was washed away, but the basic structure remained intact. However, the flooding caused by the landslide destroyed the villages of Longarone
, killing 1,450 people. Many small villages in the territory of Erto e Casso
and the village of Codissago
, near Castellavazzo
, were largely wrecked. Almost 2,000 people (some sources report 1,909) perished in total. Damage was also caused by the air displacement from the immense "splash" in surrounding villages.
Subsequent analysis of the disaster has focussed on the cause of the landslide. There remains ongoing debate about the contribution of rainfall, dam level changes and earthquakes as triggers of the landslide, as well as differing views about whether it was an old landslide that slipped further or a completely new one.
In 2001, a movie was released about the Vajont disaster, "Vajont, La diga del disonore" ("Vajont, the dam of dishonour") or "La folie des hommes" (in France), starring Michel Serrault and Daniel Auteuil. It has also featured in the documentary series Disasters.
- Franco Mantovania and Claudio Vita-Finzi, 'Neotectonics of the Vajont dam site', Geomorphology, Vol. 54, Issues 1-2, 2003, pp 33-37.
- David Petley, Landslide information: The Vajont (Vaiont) Landslide, 2001, retrieved January 2008.
- Suburban Emergency Management Project (SEMP), 'Epic Vajont Dam Disaster, Italy, 1963: Manmade or Natural?', Biot #373: June 17, 2006, retrieved January 2008.