In 1943, the Adriatic Society of Electricity, SADE, founded in 1905 by Giuseppe Volpi, received the state concessions to kick start the construction of a dam on the shore of the river Vajont. The Vajont dam was going to be among the biggest in the world at that time.
The idea of using as hydroelectric basin the valley of river Vajont was realized by the Hydroelectric Veneta Company, then absorbed by SADE, particularly active at the end of the nineteenth century and the first half of the twentieth century in the electrical distribution in northeastern Italy (before nationalization of the electricity sector implemented through the creation of a National Agency for Electric Energy: ENEL).
The reservoir is created for storing up the waters of the River Piave after their passage in the dam center Cadore, through which arrives in the tank of Vajont through pipes with minimum altitude.
The company proceeded to carry out in record time the land expropriations necessary for starting the work, sometimes using excessive pressure and force toward local inhabitants. Within a few years, of the 5,200 acres of township, 3,000 had become property of SADE.
Since the arrival of SADE on Mount Toc, local residents claimed their rights to territoriality, fighting against the expropriation of land and exposing potential flaws in the project. They formed two committees (Committee for the Defense of the Municipality of Erto and Civil Consortium for the Re-birth of Val Ertana) whose requests and complaints were never heard.
On March 22nd 1959, a landslide collapsed in the water basin of Pontesei, in Forno di Zoldo. The landslide further alarmed the inhabitants of Erto, that on May 3rd called for a meeting for the "Civil defense and the revival of the valley of Erto". Tina Merlin, a journalist and activist of the Communist Party, who was reporting from the area, was summoned for spreading false information and for contributing to public disorder. Meanwhile, the Consortium had been mobilized, demanding that "the work being done for the advancement of the nation does not lead to destruction of the local economy or endanger the safety of its citizens.”
On March 1963, the plant had officially become property of the new National Agency for Electricity, today's ENEL. In the meantime, the friction between the local authorities and the SADE had become very serious. A danger warning came in with a strong earthquake, estimated at around 7 degrees on the Mercalli scale, which caused the collapse of some houses, while others were seriously damaged.
On October 9th 1963, the landslide of the slopes of Mount Toc, already in progress, took a hasty movement. The slide caused a wave surge up to 200 meters, and flooded the valley of Piave. On it’s course, the wave broke in and swept away entire towns along the river valley: Longarone, Pirago, the banks of Fornace, Villanova, Faè and Castellavazzo; also, it damaged areas of Soverzene and Belluno.
The final count for the accident was 1,917 victims of which 1,450 in Longaronem, 109 in Codissago and Castellavazzo, 158 in Erto and Casso and 200 from other municipalities.
Immediately after the disaster, the issue of the reconstruction of houses and towns became very urgent and sensitive. The intent of the institutions was to relocate local population and houses, rebuilding this way social structure of communities. This plan was heavily criticized by the people and caused huge unrest and led to civil disobedience and organized demonstrations, which however led to poor results. The community of Erto was deported near Maniago, a neighboring town, and the Municipality of Longarone, the most affected, suffered the same fate. Another center called New Erto was built in Ponte nelle Alpi (Province of Belluno). However, despite economic aid, communities could not reconstruct their structure and the whole geography of the area was disrupted.
February 21st 1968 began the First Instance trial where the prosecution asked for charges of 21 years for all defendants for culpable disaster of landslide and flood disaster, aggravated by the anticipation of the event and multiple aggravated manslaughter. Biadene, Batini and Violin were sentenced to six years, guilty of failing to warn about the potential danger and of not starting proper evacuation on time; all others were acquitted. The predictability of the landslide was not recognized. In 1997, Montedison (which had acquired SADE) was ordered to compensate the municipalities affected by the disaster. The affair ended in 2000 with an agreement for the distribution of the burden of compensation between ENEL, Montedison and the Italian government (33.3% each).
In February 2008, during the International Year of Planet Earth declared by the General Assembly of the United Nations, in a session dedicated to the importance of proper understanding of Earth Sciences, the Vajont disaster was mentioned, along with four other events, as an exemplary case of "avoidable disaster" caused by «the failure of engineers and geologists to understand the nature of the problem they were trying to deal with».