A dam, and not only a normal dam, one of the highest dams of its time, that’s a very prestigious project, and even more so, it is an enormous investment.
Imagine a mid-sized valley in the Italian Alps, the river Piave running through it from north down to the Adriatic Sea. Not much north of the provincial capital of Belluno, a small valley, the valley of river Vajont, joins it from the east, narrowing to a gorge where it meets the Piave. Just there, smug to the hillside, on the opposite shore of the Piave, lay the village of Longarone. 1500 people, a church, a train station, hardly worth a stop.
The first two images, the Image of the Day and the historic photography (about 1950), were taken from approximately the same point. On the left side of each, you see the cleft in the mountains, the gorge of the river Vajont.
A dam is a big investment, and when you see that the project goes awry, when you get first indications of a coming landslide, and when a first landslide occurs, and when all experts tell you that there is more to come, much more, what do you do?
You may be lucky, they may be wrong, and your investment is saved. On the other hand, when they’re right, you’ve lost nothing more than you lose when you cancel the project in face of the warnings. Thus if you persist, you have some chance to get away with your money. If not, well, what’s the difference?
Such may have been the thoughts of the managers of SADE (Società Adriatica di Elettricità), and purely from an economic point of view they were right, but the difference were between 2000 and 2500 lives.
Initial reports of landslides were suppressed, journalists were sued by the company and by the government, local protests were suffocated, and even the dire warnings of an imminent landslide on the day before the catastrophe were ignored, and even worse, the people down in Longarone were kept ignorant as well. 
It is very likely that it would have been possible to at least partially evacuate the people in the danger zone, it is very likely that it would have been possible to at least begin to empty the storage lake, but nothing was done.
Finally, on 9 October 1963 at approximately 10:35pm, the whole side of mountain Toc came loose and slid down at an enormous speed of up to 110 km per hour (68 mph). 
An enormous landslide, 260 million cubic meters, crashed into the almost full storage lake, squeezing out about 50 million cubic meters of water, producing a wave that destroyed the lower houses in the village Casso on the opposite bank, 260 meters above water level, and then overtopped the dam by about 245 meters, a fuming inferno of water and mud, that crushed down upon the sleeping residents of Longarone, within an instant killing everyone but a few children, who survived by freak chance.
Wikipedia has more background information and you may also want to read the original report in Time Magazine. See the analysis of Dr David Petley for a more scientific view of the event. Marco Paolini has made a famous TV film, half theatrical recount, half documentary, showing much original footage. It is available via Google Video. Finally the Italian movie “Vajont - La diga del disonore” tries to reconstruct the events.
Now, if you expect the most dire consequences for those responsible, don’t be a fool. Too much money was involved and too many men in highest positions. In the end everybody went free.
One engineer committed suicide, and that’s ironic in itself, because the work of the engineers was sound, the dam never broke. The fault can’t be blamed to the geologists either. Their reports were correct, but ignored. It was a matter of greed and irresponsible management that led into disaster.
All images, along with those of the previous entry, were taken on Friday afternoon, a mostly sunny, partially overcast day. I used the Tokina 11-16/2.8 and the Nikon 70-300 VR. Two images were taken from Longarone up, two from the landslide, over the dam, down to Longarone, and one from just below the village of Casso, i.e. from the opposing side of the valley, down onto the aftermath of the landslide. With some images I have taken more liberties than with others 🙂
The Song of the Day is the “Dies iræ” from the 1995 recording of Verdi’s “Requiem”, directed by John Eliot Gardiner. YouTube has a video with the Berlin Philharmonic Orchestra under Claudio Abbado. Not a bad choice either.