Vajont Dam - Landslide and Wave

Landslide and Wave

On 9 October 1963, engineers observed trees falling and rocks rolling down into the lake where the predicted landslide would take place. Prior to this, the alarming rate of movement of the landslide had not slowed as a result of lowering the water, although the water had been lowered to the recommended safe level to accommodate a catastrophic landslide suddenly occurring. With a major landslide now imminent, engineers gathered on top of the dam that evening to witness the tsunami.

At 10:39 pm, a massive landslide of about 260 million m3 of forest, earth, and rock, which fell into the reservoir at up to 110 km per hour (68 mph) completely filled up the narrow reservoir in front of the dam. The landslide was much faster than predicted, taking just 45 seconds, and the resulting displacement of water caused 50 million m3 of water to overtop the dam in a 250-metre-high (820 ft) wave.

The flooding from the huge wave in the Piave valley destroyed the villages of Longarone, Pirago, Rivalta, Villanova and Faè, killing around 2,000 people and turning the land below the dam into a flat plain of mud with an impact crater 60 metres deep and 80 wide. Many small villages near the landslide along the lakefront also suffered damage from a giant displacement wave. Villages in the territory of Erto e Casso and the village of Codissago (it), near Castellavazzo, were largely wrecked.

Estimates of the dead range from 1,900 to 2,500 people, and about 350 families lost all members. Most of the survivors had lost relatives and friends along with their homes and belongings.

The dam itself was largely undamaged — the top metre or so of masonry was washed away, but the basic structure remained intact and still exists today.