History Daily - The Vajont Dam Disaster

Episode Date: October 9, 2025

October 9, 1963. A long-predicted landslide in northern Italy triggers a tsunami-like wave to spill over the Vajont Dam, killing over 2,000 people and constituting one of the worst man-made environmental disasters in history.  This episode originally aired in 2023. Support the show! Join Into History for ad-free listening and more.History Daily is a co-production of Airship and Noiser.Go to HistoryDaily.com for more history, daily.

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This-huh. In fact, can-halloumit-Tortilla, now, 5 p.m. On the evening of October 9th, 1963, in Longarone, a small village in the Piavi Valley

in the Italian Alps. Twelve-year-old Mikhaila 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 Biont 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 Michaela'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, Michaela stays silent as her father abruptly stands up and walks out the front door, headed to the dam for a late shift. Mikaela 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 good night. But before her mother can arrive, Michaela jolts upright at what sounds like a large thunder clap, followed by an odd rumbling. As the sound grows louder, Michaela's grandmother enters the room and tells her a storm must be approaching. She closes the shutters on Michaela's window, and at that exact moment, all the lights in the house go out.

Then, without warning, Michaela feels her bed shudder. 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 Michaela in debris. Michaela Coletti will be one of only 30 children to survive that giant inland tsunami, triggered by a landslide into the Viant Dam's reservoir. Proceeding the wall of water will be an air pocket so strong that almost all its victims would be found naked, their clothes blown off by the blast. Though the dam will survive, Mikhaila'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 reeks on October 9, 1963. The next one-en-kerrocksenra bests, alcoed anteroomboimata, when his wholesome

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Puhlililililii. Pujliii and all-liteiteite On etunnnatt Elisan I'm Ed Olisiya. Before we get back to the show, a super quick announcement. You've probably heard another super quick announcement recently

that I'm hoping to hit the road with a History Daily Live show, and I told you to go to historydaily live.com to sign up for info. But that form was broken, and some of you received an error message. It had something to do with a misconfigured SSL certificate causing a 301 redirect loop, and if you understand that, I should have come to you when setting it up. But it's working now better than ever. So if you've tried before and did get an error message, please head to historydailylive.com and let me know your home city so I can plan this tour.

And if you haven't tried before, please head to historydaily live.com and let me know your home city so I can plan this tour. That's historydaily live.com. Let's make history live and in person, historydaily.com. From Noisor and Airship, I'm Lindsay Graham, and this is History Daily. History is made every day. On this podcast, every day, we teach. tell the true stories of the people and events that shaped our world. Today is October 9, 1963, the Viant Dam disaster. It's November of 1960 in northern Italy, three years before an inland tsunami will ravage Italy's Piabe Valley. Italian engineer Carla Semenza watches carefully as the water level of the reservoir behind the Viant 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, Carlos 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 Valyant 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, 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 Viant 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 Viant Dam was to be built adjacent to Mount Tau. 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 is 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. On phased 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 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 risk surrounding the struggle. that Carlo, 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 Talk. It careens down a cliffside 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 Talk 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 Bayot Dam still presents grave dangers to the residents below it. And over the coming months, Carlo will try to take further action, drawing his boss's attention back to the dam's risks and advocating for greater safety measures, but it won't be enough to prevent catastrophe. Five-and-sixtheaden in between, pickunoita pestess, alcoed anterrae hoomata, when his valetton huomions,

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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 had warned of an impending landslide in this very location, and two years ago, the dam's designer tried to intervene. In 1961, Carlos 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 the research. But sadly, he didn't live to see his recommendations implemented. With the stress of the project continuing to wear on him, Carlos suffered a cerebral hemorrhage and died in October of 1961,

leaving his son Eduardo to take over the work on the Viant 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 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 Viant Dam to change hands from the Adriatic Electric Company to the National Agency for Electricity. While Eduardo Semenza and local authorities in the Piabe Valley continued to advocate for more research and pushed for preventative 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 Carlos Amenzza, 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 had nothing to worry about. But many of the valleys 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 Talk and the entire mountain slides slid by almost nine 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 be.

remain skeptical of their safety, few will predict the amount of damage and destruction that's coming. It's the evening of October 9, 1963. At a pub in Langaroni, patrons gathered 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 Talk. But as the clock hits 1039 p.m., that quickly changes. The landslide generates a seismic shock, and within 45 seconds, the Viant Reservoir is overwhelmed.

The water builds into a tsunami that sweeps through Longorone, 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 a primary road completely down. decimated by flooding. When relief workers do make it to Long Gironi, they find a community utterly destroyed. When the damage is finally surveyed, Long Garoni 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 was 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 largest share of the blame will fall in 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 Viant Dam will stay standing.

Ironically, it will be one of the few structures that survives the tsunami, though it will subsequently cease operations. Today, the dam is a tourist attraction, the site of guided tours, a relic reminding observers of the immense loss of life that perhaps could have been avoided if more warnings were heated before the landslide that triggered a calamity on October 9, 1963. Next, on History Daily, October 10, 2014. Two years after being shot by a gunman, 17-year-old education activist Malala Yusufzai wins the Nobel Peace Prize. From Noisor and Ayrship, this is History Daily, hosted, edited, and executive produced by me,

Lindsay Grant. Audio editing by Mohamed Shazi, sound design by Katrina Zemrak, Music by Lindsay Graham. This episode is written in research by Scott Weiss. Executive producers are Alexandra Curry-Buckner for Airship and Pascal Hughes for Noisor.