The Vajont Dam disaster’s huge reservoir wave occurred in Italy. The dam and reservoir were in the Vajont Valley in northeastern Italy, near Longarone and Erto e Casso.
On 9 October 1963, a massive landslide from Monte Toc plunged into the reservoir. The impact displaced roughly 115 million cubic metres of water and produced several waves. One surged over the dam crest in a wave estimated at about 250 metres, then raced into the Piave Valley and devastated Longarone and nearby communities.
The concrete dam itself remained largely intact, which is why the disaster is often misunderstood as a dam failure. The catastrophe instead resulted from the unstable mountainside, reservoir filling and failures to act adequately on geological warnings. Official figures record 1,917 deaths, though some accounts give slightly different estimates.