NARRATOR: 1957.
70 miles from Venice, amid the cliffs and gorges
of Italy's Vajont River Valley, work begins on the Vajont
Hydroelectric Dam.
Crucial to the dam's operation is
a vast reservoir that can hold 44 billion gallons of water.
Ever since the filling of the reservoir in early 1960,
enormous cracks have begun appearing on Mount Toc,
above the dam.
LUCIA FILIPPIN (IN ITALIAN): People
could sense that something big was about to happen
because the ground was moving and suddenly,
new cracks would appear, very deep and very large.
NARRATOR: Then, in late 1960, another warning sign.
This time, it's a landslide.
Though relatively small, it prompts a flurry
of scientific research.
What it confirms is shocking.
As a direct result of filling the reservoir,
Mount Toc has become waterlogged,
dislodging a 720 million ton chunk of rock that
is now slowly slipping down the mountain towards the lake
below.
And so, in 1962, the authorities lower
the water by over 70 feet.
At that level, they are confident the dam can't
be overtopped, provided the landslide falls
into the reservoir at the speed they expect.
Even as locals grow uneasy, officials
remain confident that the threat is minimal.
FRANCESCO NICCOLINI (IN ITALIAN):
No one had been warned in Longarone.
There were no official warnings.
There were just the warnings coming from the mountain.
NARRATOR: October 9, 1963.
Traveling at over 60 miles an hour, three times faster
than expected, the mile and a half wide chunk of rock
is finally unleashed.
In its sights-- the enormous Vajont reservoir.
FRANCESCO NICCOLINI (IN ITALIAN):
How can you imagine nine billion cubic feet of rock
breaking away from a mountain and falling into a basin
filled almost to the brim?
NARRATOR: It sends two giant waves in opposite directions,
one towards the dam, the other towards the village of Erto.
Traveling in over 30 miles an hour,
the first wave engulfs farms and houses all along the shore,
killing most of their occupants.
Shielded by a spur in the mouth, the village of Erto
is miraculously spared the worst of the wave.
At the opposite end of the reservoir,
the second tsunami is now hurtling
towards the Vajont Dam.
It sends more than 275 million tons of water over the edge
and into the valley below.
In its crosshairs, nearly 5,000 inhabitants of Longarone,
with nowhere to run.
The town is gone, reduced to little
more than mud and rubble.
Of the town's 372 buildings, just 22 are still standing.
The rest flattened and washed away down the Piave River,
towards Venice.
ELISA DI BENEDETTO: Longarone was not there anymore.
They could see that Longarone didn't exist anymore.
There was only mud and water and ruins.
No life at all.
NARRATOR: The violent disaster claimed almost 2000 lives,
making it one of the worst man-made disasters in history.