Vajont disaster, what happened on October 9, 1963

Sixty years ago the tragedy in which 1,910 people died, including 487 minors. The town of Longarone and the surrounding municipalities were hit

On the evening of 9 October 1963 at 10.36 pm, in the artificial hydroelectric basin of the Vajont torrent, on the border between Friuli-Venezia Giulia and Veneto, a gigantic landslide (over 270 million cubic meters of rock) fell from the slope of Monte Toc above into the waters of the Alpine basin causing the overflow of the water contained in the dam reservoir. The waves, one of which exceeded the crest of the dam by more than 250 m in height, first hit Erto and Casso, towns close to the lake shore, and then flooded and destroyed villages on the Veneto valley floor, including Longarone. The victims were 1,910, including 487 minors.

The construction of the dam

Construction work on the dam, designed by the engineer Carlo Semenza, began in 1957 and the slope above the dam was immediately kept under control. For three years, in fact, various experts were consulted: however, none of them managed to identify the paleolandslide (accumulation of loose material along a slope due to a landslide that occurred in ancient times) which would later be seen as the determining cause.

The first alarms

Before the great landslide there were two signals: the first in 1959when 3 million m3 of rock collapsed in the Pontesei basin, one of the basins of the Grande Vajont system without however causing damage, the second instead November 4, 1960, when a small landslide occurred in the Vajont dam basin and caused a two-meter wave. Despite these warnings, the concern of Carlo Semenza himself and the involvement of experts, it was not possible, through the evaluation and interpretation of the territory, to prevent the tragedy that occurred three years later.