Cold Open

It’s 5 PM, on the evening of October 9th, 1963 in Longarone, a small village in the Piave Valley in the Italian Alps.

12-year-old Micaela Coletti tries to enjoy a quiet dinner with her family, but there’s tension in the air. Rumors have been circulating around town about serious problems at the Vajont Dam where her father works. Three years ago, the dam was built in an area prone to landslides. And many speculate that disaster is just around the corner.

Over dinner, the discussion between Micaela’s parents turns heated. Her mother ominously suggests that it might be better to send the kids away but her father disagrees.

He slams his fist on the table and declares that if the dam collapses and the family must die, it would be better to die together.

Terrified, Micaela stays silent as her father abruptly stands up and walks out the front door, headed to the dam for a late shift.

Micaela wordlessly helps her mother clear the table, before walking to her room. As the hour grows late, she gets into bed and pretends to sleep, waiting for her mother to come kiss her goodnight.

But before her mother can arrive, Micaela jolts upright at what sounds like a large thunderclap, followed by an odd rumbling.

As the sound grows louder, Micaela’s grandmother enters the room and tells her a storm must be approaching.

She closes the shutters on Micaela’s window. And at that exact moment, all the lights in the house go out.

Then, without warning, Micaela feels her bed shutter. The floor is yanked out from under her and, suddenly, she’s thrust high into the air as a 246-foot wall of water engulfs the village, washing away the Coletti’s home and burying Micaela in debris.

Micaela Coletti will be one of only thirty children to survive the giant inland tsunami triggered by a landslide into the Vajont Dam’s reservoir. Preceding the wall of water will be an air pocket so strong that almost all its victims will be found naked, their clothes blown off by the blast. Though the dam will survive, Micaela’s parents, sister, and grandmother, along with 2,000 others, will not.

But this tragedy will not just be an unfortunate natural disaster. In its wake, old warnings regarding the dam’s poorly chosen location and the area’s well-known risk of landslides will take on a new gravity, and the devastating tsunami will instead be labeled one of the worst man-made environmental disasters, thanks to the destruction it wreaks on October 9th, 1963.

Introduction

From Noiser and Airship, I’m Lindsay Graham and this is History Daily.

History is made every day. On this podcast—every day—we tell the true stories of the people and events that shaped our world.

Today is October 9th, 1963: The Vajont Dam Disaster.

Act One

It’s November of 1960 in Northern Italy, three years before an inland tsunami will ravage Italy’s Piave Valley.

Italian engineer Carlo Semenza watches carefully as the water level of the reservoir behind the Vajont Dam begins to rise.

For the past three years, Carlo has been hard at work overseeing the construction of the Dam. But the project has been in development far longer.

Way back in the 1920s, Carlo started designing the structure. He wanted to build the tallest dam in the world, something capable of harnessing three of the region’s rivers to meet Italy’s growing demand for power and industrialization. But as the country fell into social and political turmoil under Dictator Benito Mussolini, the project was put on hold. It took until 1943 before the dam was approved by the Italian government, and until 1957 for construction to even begin.

Carlo has operated as the brains behind the operation, planning the miles of concrete pipes and bridges that will stretch across the Vajont Gorge. But it is actually the Adriatic Electric Company that has overseen the project.

Launched in the 1800s, this company is the brainchild of Italian engineering professor Giuseppe Colombo. Colombo, an admirer of Thomas Edison, successfully secured exclusive licenses to some of Edison’s patents and began using them to build power-generating projects around Italy. By the 1950s, the Adriatic Electric Company had grown into a monopoly, controlling power distribution across most of northern Italy. The Vajont Dam became one of its most ambitious projects, and the powerful Adriatic Electric Company was able to successfully acquire the land needed for it, despite resistance from residents of the valley communities below.

The locals were concerned because the Vajont Dam was to be built adjacent to Mount Toc, known to locals as the “walking mountain,” for its frequent landslides. But those concerns were overruled and the dam now stands as an impressive feat of engineering. At a height of 860 feet, it is the tallest dam in the world built to this point. And it’s sure to provide much-needed electricity for the fast-growing country and to become a major employer in the area. But still, there’s a problem.

As part of his engineering work, Carlo hired his son, Eduardo, to conduct research on the area’s geology. And in doing so, Eduardo discovered a significant ancient landslide that he believed was likely to repeat itself. He drew detailed maps, took photos, and presented his findings to his father, who in turn presented the data to the Adriatic Electric Company. But the Semenza's concerns were given little weight. Unfazed by the research, the Adriatic Electric Company instructed Carlo to proceed with the project.

So he did. And within three years in February of 1960, the dam was built and the Adriatic Electric Company received authorization to begin filling its reservoir.

But the potential hazards his son Eduardo revealed lingered in Carlo’s mind. Over the summer, Carlo and his team continued to observe landslides and earth movements, and the project began to attract the attention of journalists. The media’s scrutiny was quickly shut down by the Italian government, which pursued legal action for any unfavorable reporting. And since then, the project has moved full steam ahead. But there’s no denying the risks surrounding the structure that Carlo and many others hope will be a post-war economic miracle.

Today, Carlo watches as the reservoir is filled to testing levels. It should be an exciting landmark in the dam’s development, but Carlo is uneasy, and for good reason. As the water rises, a small landslide suddenly begins to fall from Mount Toc, it careens down a cliff side and right into the reservoir, where it generates a six-and-a-half-foot wave.

Fearing the worst, Carlo immediately calls for the reservoir to be drained. His team begins to take down the water level – slowly, so the removal doesn’t further destabilize the mountain. And once it’s down to a safe level, engineers begin building a drainage gallery in the basin in front of Mount Toc, to help redirect water in the event of additional landslides.

Carlo worries this won’t be enough to stave off disaster. It’s clear to him that the Vajont Dam still presents grave dangers to the residents below it. And over the coming months, Carlo will try to take further action, drawing his bosses’ attention back to the dam’s risks and advocating for greater safety measures. But it won’t be enough to prevent catastrophe.

Act Two

It’s the morning of October 9th, 1963, in the Italian Alps, three years after the Vajont Dam was completed.

In an area near the new dam, a group of engineers stand together as they begin to witness an unsettling series of events. Trees, which had once stood strong now tumble down the mountainside, while rocks roll into the reservoir behind the dam. Each splash and tumble forms an unnerving crescendo and a palpable sense of foreboding grips the engineers.

For years, researchers have warned of an impending landslide in this very location. And two years ago, the dam’s designer tried to intervene.

In 1961, Carlo Semenza submitted a letter to his superiors calling attention once again to the ancient landslide his son discovered, and to the small landslide that interrupted the reservoir’s test filling. For Carlo, this was enough evidence that landslides will occur in the future. And when they do, they could cause giant waves of water to rise over the dam and flood the villages below.

In response to Carlo's letter, the Adriatic Electric Company built a physical-hydraulic model to perform experiments on the effects of a landslide fall into the reservoir. In the first set of experiments, researchers used gravel to simulate a sliding mass. But they found it near impossible to reproduce the geological phenomenon of a landslide.

So, they turned to Carlo to make adjustments. As an innovative engineer, he came up with a number of solutions to help improve their research. But sadly, he didn’t live to see his recommendations implemented. With the stress of the project continuing to wear on him, Carlo suffered a cerebral hemorrhage and died in October of 1961, leaving his son Eduardo to take over the work on the Vajont Dam.

Experimental fillings of the reservoir continued through 1962. And initial testing confirmed Carlo’s hypothesis, demonstrating that the reservoir is indeed susceptible to landslides which could lead to a catastrophic tsunami wave if not addressed. So, the Adriatic Electric Company agreed to make even more changes. In July of that year, they decided to keep the reservoir’s water level 82 feet below the top of the dam. According to their testing, this was a safe level, low enough that a wave generated by a landslide could not breach the crest of the dam.

The following year, the nationalization of Italy’s power industries forced the Vajont Dam to change hands from the Adriatic Electric Company to the National Agency for Electricity. While Eduardo Semenza and local authorities in the Piave Valley continued to advocate for more research and push for preventive safety measures, the Italian government refused to take a step back. The dam was a major economic investment that they refused to abandon.

And as the project forged ahead, communication between government agencies, engineers, and local authorities reached an all-time low. In the absence of a leader like Carlo Semenza, numerous competing factions arose, vying for power and management of the dam. All of this was exacerbated by the government, who took steps to silence any journalists attempting to report on the realities and dangers of the project. The National Agency for Electricity continued its narrative that the dam was fine, and local residents have nothing to worry about.

But many of the valley’s villagers did not believe this. And as they started to notice more slides, shakes, and movements of the ground, the residents raised alarm bells over the summer. But their worries fell on deaf ears and achieved nothing. So even as tremors continued to shake the valley, the new engineers in charge of the dam assured the public that everything was under control.

But it quickly becomes apparent that it is not. The month prior an earthquake shook Mount Toc and the entire mountainside slid by almost 9 inches, a huge distance for a mass so big.

Now, the engineers cannot ignore the signs any longer. And today, a complete landslide looks inevitable. A sense of dread hangs heavy in the air as they grapple with the realization that a long-predicted disaster is unfolding before their eyes.

Quickly, word will begin to travel through the nearby villages that something is amiss. Officials will try to ease the alarm, claiming that the dam’s reservoir is low enough to prevent any major flooding. And uncertain of the dangers, most residents will stay put. No mass evacuations will take place. And though many will remain skeptical of their safety, few will predict the amount of damage and destruction that's coming.

Act Three

It’s the evening of October 9th, 1963.

At a pub in Longarone, patrons gather together to watch a European Cup soccer game between Real Madrid and the Glasgow Rangers. Right now, they have no idea that high above the valley, a 1.2-mile landslide containing forest, earth, and rock has begun to fall off Mount Toc.

But as the clock hits 10:39 PM, that quickly changes.

The landslide generates a seismic shock and within 45 seconds, the Vajont reservoir is overwhelmed. The water builds into a tsunami that sweeps through Longarone, destroying everything in its path. The patrons at the bar can hardly register what hit them as the water, filled with earth and debris, descends upon them.

Firefighters and rescue responders struggle to reach the valley with the primary road completely decimated by flooding. When relief workers do make it to Longarone, they find a community utterly destroyed. When the damage is finally surveyed, Longarone, and the surrounding villages, are left in shambles, reduced to a flat plain of mud with an impact crater 200 feet deep and 260 feet wide.

By the early morning hours, a major rescue is underway with 850 divers, land and helicopter teams, combat engineers, and firefighters working to find survivors. All told, an estimated 2,000 to 2,500 people will perish in the disaster.

The Italian government will attribute the tragedy to an unexpected and unavoidable natural event. But researchers and engineers like Eduardo Semenza know better. Ultimately, the larger share of the blame will fall on the Adriatic Electric Company and the National Agency for Electricity, who for years had seen, and ignored, research that suggested that a catastrophic event was likely.

Though the valley’s communities will eventually be rebuilt, they will be completely different from the old villages that were destroyed. Amidst the devastation, the Vajont Dam will stay standing. Ironically, it will be one of the few structures that survive the tsunami, though it will subsequently cease operations. Today, the dam is a tourist attraction, the sight of guided tours, a relic reminding observers of the immense loss of life that perhaps could have been avoided, if more warnings were heeded before the landslide that triggered a calamity on October 9th, 1963.

Outro

Next on History Daily. October 10th, 1970. In their fight for Quebec’s independence, members of a radical separatist group kidnap a government official in Montreal, sparking national panic.

From Noiser and Airship, this is History Daily, hosted, edited, and executive produced by me, Lindsay Graham.

Audio editing by Muhammad Shahzaib.

Sound design by Katrina Zemrak.

Music by Lindsay Graham.

This episode is written and researched by Scott Weiss.

Executive Producers are Alexandra Currie-Buckner for Airship, and Pascal Hughes for Noiser.