Italy Vajont disaster: The man-made Pompeii of Northern Italy

Oct 9, 20193 min read

How the Vajont Dam dam flood wiped away the Piave valley and its citizens

Fifty-six years ago Europe woke up to news of a disaster that struck a mountain valley, 100km north of Venice. A land slide caused an overflow of the 260m higher artificial Vajont lake and flooded with heavy force the small town of Longarone. In just a few seconds, over 2000 people where killed. Whole families and communities were married under mud.

The view of Pirago. Miraculously, the village's bell tower survived. Photo: Ispettorato Vigili del Fuoco

September 1959. We’re in Longarone, a town on the West side of the Piave Valley linking Veneto with Austria, in the middle of the Dolomites. On the other side of the valley, there is a steep gorge leading to the mountain villages of Casso and Erto. In this narrow gorge, the Italian Società Adriatica di Elettricità (Adriatic Energy Corporation) manages to build the tallest dam in the world after almost 3 years of construction. Measuring 261.6 metres in height and 191 metres in width, it could held up some 168,715,000 cubic meters of water. It was a mayor construction in the bigger ‘Grande Vajont’ project that would generate 220MW, enough to power about 50 000 homes these days.

The early signs of disaster

However, the glory didn’t last long. Only 9 months after they started filling the bassin, a landslide of about 800,000 cubic metres collapsed into the lake on November 4th 1960. At the time the water level in the reservoir was at about 190 metres of the planned 262 metres. Several studies had already shown that the region was geologically unstable and a landslide at the nearby Pontesei dam had created a 20-meter high wave that killed one person only a year before. Geologists stated that the whole side of The Vajont lake could collapse once ‘its feet’ would be put under water. Instead of listening to the geologists, the constructor SADE assured that the mountain was stable and sued the Italian journalist Tina Merlin for spreading fake news in order to create panic and to abolish the economically very important project of which the plans and authorisation were made in 1943, right after the fall of Mussolini, by a post-fascist government during the second world war.

After the first landslide however, SADE stopped the filling, lowered the water level by about 50 metres, and started to build an artificial gallery in the basin in front of Monte Toc to keep the basin usable even if additional landslides (which were expected) divided it into two parts. After one year, in October 1961, the gallery was completed and they refilled the bassin up to 215 meters. Even though in April and Mai 1962, 2 earthquakes of grade five were reported, SADE as authorized to fill the bassin to its maximum capacity.

In March 1963, the dam was transferred to the newly constituted government service for electricity: ENEL. During the following summer, with the basin almost completely filled, slides, shakes, and movements of the ground were continuously reported by the alarmed population. On 15 September, the entire side of the mountain slid down by 22 centimetres. On 26 September, ENEL decided to slowly empty the basin to 240 metres, but in early October the collapse of the mountain's south side looked unavoidable: On October 9th 1963 at 10:39 PM, 260,000,000 cubic metres of forest, earth, and rock fell into the reservoir at up to 110 kilometres per hour.

One of the biggest Tsunamis in history

This mass, which could only be transported by 9 million big dump trucks, caused a 250m high wave that first touched the lower houses of Casso, located 250m higher on the other side of the lake Casso. Forty-five seconds later, the water made its way down the gorge, towards Longarone.

The wall of water pushed an air pocket before it. It was more powerful than the Hiroshima bomb. So strong, in fact, that almost all the victims were found naked, their clothes blown off by the blast.

The dam survived but 80% of the inhabitants of Longarone and its satellite villages did not. In all, 1909 people are known to have died - but the final death toll will never be known. About 446 bodies were never recovered and another 761 never identified.