Vaiont Dam Disaster, Italy

Vaiont Dam, Dolomite Mountains, Italy

This landslide pushed a reservoir over Europe's tallest dam and killed over 2000 people in 1963. 

Why Visit?
This place moved me as much as any other I've visited in Italy, including Pompeii and the Vatican. There is such personal tragedy attached to this landslide, you can feel it when you visit. This was a bizarre and tragic event that taught the world new science and forever changed the way reservoirs are chosen. In a majestic and beautiful setting, it's also convenient to all of NE Italy's best destinations including Venice and Cortina (site of the 1956 Winter Olympics).

Travel to Longarone

Logistics: This is a good add-on to your trip to northeastern Italy to Venice, Padua, Vicenza, Trieste, or the Dolomites.
Vehicle: You'll need to rent a car at Mestre or wherever your other travels have led you. Don't worry - driving in the Italian countryside is not the demolition-derby-terror of driving in the cities! But you will encounter a lot of fast, enthusiastic drivers on the mountain roads, so keep your eyes open and don't dawdle! If you rent a car in Mestre, get a GPS unit in your car (they're pretty standard), have them teach you how to use it, and follow it religiously! Mestre is incredibly confusing.
Lodging: Longarone is off the tourist-beaten path, so your best bets for lodging are to the south at Vittorio Veneto, the Venice-Mestre area, or in the mountains at Cortina d'Ampezzo. Reasonable rates can be found at all these areas.
Time: Minimum 2 hours to see the dam and landslide. My group of geologists spent all day, of course!
Food: Longarone is not a tourist area, so look for the hometown eateries or do like we did and explore the grocery store!
Difficulty: Easy for anyone. You can even drive onto the landslide and see a lot from your car.

Geology of the Disaster

The Vaiont Dam is located east of the town of Longarone in the Piave River valley directly north of Venice in the Dolomite Mountains (the eastern Alps). The dam is called "Diga del Vajont" on the Google Map above. The Alps and Dolomites were created during collision between the European and African tectonic plates. Former continental shelf rocks were piled on top of each other in great, thick slabs. Deformation and metamorphism are less in the Dolomites than in the western Alps, creating a distinct landscape characterized by layered earth-tone cliffs and rocky slopes. The mountains have been deeply eroded by streams and glaciers to create the deep valleys and majestic, steep mountains we see today. And that's what set up this disaster!

The dam site was a natural choice - a very narrow, deep canyon with storage space for a reservoir. But the canyon had a fatal geologic flaw that no one realized the implications of - the bedrock on the south side is tilted down toward the valley. Some say that in addition, an ancient landslide was sitting on this tilted slope. Over time, the river had undercut the lower parts of the landslide and the tilted bedrock layers, leaving them hanging on the slopes only by friction. 

This cross-section shows an ancient landslide perched on tilted bedrock above the reservoir. Existence of the ancient landslide is debated among geologists.  From Earth Magazine, Oct. 2013   

During filling of the reservoir, small landslides were noted, but they were surficial material and gave no hint at the deep-seated bedrock landslide that was to follow.

On October 9, 1963 at about 10:28 p.m., the Vaiont landslide gave way. 270 million cubic meters of rock filled the valley and the reservoir, sending a gigantic wave up the mountainside and over the dam. It hit the town of Longarone with devastating force and continued down the Piave River valley in the darkness. In just a few minutes, over 2000 people were dead, including over 750 children. 

Investigations in the subsequent years taught geologists and engineers the importance of pore pressure. It had been known for decades that injecting water into bedrock deep in wells could substantially weaken the rock, causing it to fracture. This is what's known as "fracking" today in oil and gas wells. What was not known in 1963 was that filling a deep reservoir could create sufficient pore pressure to weaken bedrock enough to cause it to fail. That's what happened at Vaiont - filling the reservoir injected water into the bedrock under high pressure, causing it to weaken significantly and fall into the reservoir. The landslide slid on a thin layer of shale, only 5 to 15 cm thick, but it was tilted down toward the reservoir, and that made all the difference.

More than 2000 people died. More than 350 families lost all members. Over 750 children perished.

The drive up the Piave River valley is quite pleasant! The Vaiont dam is in the deep notch below the snow-capped peak.

Longarone is a quiet little town in a majestic setting.

Memorial to those from Longarone who died in World War I. That's Vaiont canyon behind it.

The Vaiont Canyon and dam from Longarone. While we were at this spot, an elderly gentleman told us all about the flood. He was in another town seeing a movie with friends, and his entire family was lost. His voice was colored with painful acceptance of loss.

I asked him how high the flood wave got, and he pointed to that house high on the hill. "It got all the way up there," he said.

The road to the dam has switchbacks north of Longarone, then goes through tunnels to get above the dam. See the tunnel windows?

You'll drive through a series of tunnels to get up to the dam. Stop lights allow traffic in one direction at a time.

The Vaiont Dam is promoted on this travel website:  Click Here. The memorial chapel overlooks the dam and the landslide.

This touching statue at the memorial chapel looks mournfully at the landslide.

The dam survived the landslide, which came within about 100 meters of hitting it. Half of the 240 meters (800 foot) dam is buried in mud. For scale, can you see the man on the dirt road?

We visited in 2013, the 50th anniversary of the disaster. Each flag has the name and age of a child who was killed in the flood. The flags go all the way down to the memorial chapel. It was truly moving.

This sign greeted us, reminding us to never forget the children under 15 who died in the flood.

Each flag, a life cut short.

At the chapel, you can see the landslide where the reservoir was (at left), the scar where the landslide came from (high left), and the dam.

The rock culprit - the thin layer of pinkish shale below the blue & orange stained cliffs was the glide plane for the landslide. This exposure is just north of the dam.

This sign at the visitor center explains the strata of the landslide (bracketed in orange). The shale is the thin zone with dashed lines (a symbol for clay).

A look at the landslide. Grasping the incredible size of this landslide is one of those things you really have to see in person to appreciate, like the Grand Canyon or Crater Lake. Where the reservoir was, a mountain now is. It's incredible!

From just up the canyon, the landslide (left) is hundreds of feet higher than the reservoir used to be. It not only filled the 800 foot (240 meter) canyon, it is now much taller.

This large section of the landslide shows that much of the bedrock is still intact, though folded and rotated. In that sense, it is truly a "slide," meaning a displaced block that is still intact.

This part of the landslide shows how the bedrock was broken up and tilted as it slid.

A panorama of the landslide scar. It is 2 km (1.4 miles) wide east-west and up to 610 meters (2000 feet) tall. In this picture you can see that the bedrock is tilted down toward the valley (in geologist terms, the bedrock dips north). 

A close-up of the west end of the scar, viewed from on the landslide east of the dam.

A view of the east half of the scar from on the landslide.

Looking down the valley past the dam from on top of the landslide. Where a deep reservoir once was, is now a series of lumpy hills. Longarone lies in the valley beyond the first, dark hills.

Looking north from on top of the landslide, you'll see the village of Casso, one of the most scenic mountain villages I've ever seen. The wave from the landslide reached the lower end of the village, 250 meters (820 feet) up. Due to ongoing geologic hazards in the area (see the avalanche debris to the right of the village?) it was evacuated in 1971 after being inhabited since 1558, and now lies empty except for special events.

The solid slabs are limestone below the landlide mass. The remnants being eroded and gullied are shaley or thin-bedded strata. Small landslides and debris flows are ongoing hazards here.

A close-up of the ongoing landslide and debris flow hazards.

The eastern end of the landslide clearly shows the tilted bedrock layers. The culprit clay was on those slopes, and when the rock below became overly weakened, the landslide slid down the shale.

Another view of the east end of the landslide. The green hills are the landslide.

This view shows how thick and massive the landslide is - it's everything between the camera and the bare scar.

There is hope in the canyon! View upstream from the east end of the landslide.

A view back toward Casso on the mountainside above the dam, seen from the high east end of the landslide.

Vaiont Lake is all that remains of the reservoir. The stream is now piped under the landslide down to the Piave River valley. View looking east, upstream.

View westward of the landslide and scar. From the bottom of the former valley here to the top of the landslide mass is over 425 meters (1400 feet). That's a thick landslide!

Now, while you're in the area...

It's worth a drive to Cortina d'Ampezzo. This charming village is on the way.

Cortina was the site of the 1956 Winter Olympics. It's a fantastic Alpine valley that will take your breath away any time of the year. It features world-class skiing in winter and world-class hiking and mountain biking in summer.

Related Pages:  Venice

Related Websites:
About the landslide
A simulation of the "tsunami"