Vajont Dam

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The Vajont Dam as seen from Longarone today, showing approximately the top 60-70 metres of concrete. The 200-250 metre wall of water (megatsunami) that over-topped the dam would have obscured virtually all of the sky in this picture.

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.

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; calculations ordered by management showed that catastrophic failure was unlikely and the valley side could be stabilized over time in this manner. Thus the reservoir was filled and slowly emptied three times. However, Italy was in the process of nationalizing electric utilities (today all electricity is provided by ENEL) and SADE was very anxious to sell the dam and its generators to the newly formed state-owned electric company.

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. 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, Pirago, Rivalta, Villanova and Faè, 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 caused from the immense "splash" in surrounding villages.

In 2001, a movie was released about the Vajont disaster, "Vajont, La diga del disonore" (Italy) or "La folie des hommes" (France), starring Michel Serrault and Daniel Auteuil.