Vajont Dam : The Deadliest Dam Tragedy in Human History

The Vajont Dam disaster was a catastrophic landslide that generated a massive tsunami, killing over 2,000 people. Although the dam itself was robust and survived the event, engineers and authorities disregarded warnings about the potential for landslides and prioritized the hydroelectric project, resulting in a preventable tragedy due to human negligence.

Dam Construction

• 00:00:41 The Vajont Dam was built in a narrow valley between two mountains, utilizing strong rock formations for support and maximizing cost savings. Despite local knowledge of landslides in the area, engineers were confident in the dam's design, including a double-curvature arch, and increased the dam's height to 260 meters, making it the tallest dam at the time.

Landslide Risk

• 00:02:30 Mount Toc, the mountain above the dam, had a hidden clay layer that acted as a slip surface, increasing the risk of landslides. Water from the reservoir percolated through the limestone, weakening the clay and exacerbating the instability, leading to a series of smaller landslides after the dam's construction began.

Engineering Experiments

• 00:04:00 Engineers conducted model-based experiments to assess the impact of a large landslide, concluding that a high-speed landslide could be catastrophic, resulting in a tsunami that could overtop the dam. These studies warned that the dam might survive but that downstream villages would be destroyed, but the warning was disregarded.

Water Level Management

• 00:05:53 Engineers attempted to control the landslide by manipulating the water level in the reservoir, believing they could control the rate of the landslide using drainage tunnels. Despite initial success in slowing down the landslide by lowering water levels, they later continued to fill the dam, increasing the risk of a large-scale landslide.

Landslide and Tsunami

• 00:08:53 On October 9th, 1963, a massive landslide occurred, moving 260 million cubic meters of rock at over 90 km/h. This created a 350-meter-tall tsunami that overtopped the dam, destroying the town of Longarone and several nearby villages, resulting in over 2,000 deaths. The disaster highlights the consequences of ignoring warnings and prioritizing profit over human safety.