5. Landslides

5.1. Italy

In Italy, slope failures occur every year, claiming lives, causing economic disruption, and producing different environmental problems. In Italy, intense or prolonged rainfall is the primary trigger of landslides, but also the hydrogeological instability due to human activities.

One of the major disaster was the Vajont dam, which happened on the evening on 9th October 1963.

It was caused by the fall of a 270 million m3 landslide from Mont Toc into the artificial lake, made by a 200m dyke.

This giant rock mass made the water into the bacin overflown.

After that the water caused the flood, the destruction of the city of the Venetian valley bottom, among which Longarone, and the death of almost 2000 people.

A lot of people also died in the district of Codissago and Castellavazzo.

Some aspects of human error that may have contributed to the landslide could have been due to the time in which this construction took place, as levels of technology were not well enough advanced to show accurate findings. When engineers knew that a tsunami could have been a possibility, they conducted a scale simulation to find out if the dam could hold back a tsunami wave if one did occur. They investigated this by changing the speeds at which a possible landslide could occur and observing whether the dam could hold back the height of the wave that these speeds could produce. However as this was not a computer simulation they could only estimate how long the landslide would take to fall. It is thought that if a computer simulation was possible at the time then a correct estimation of the size of the wave would have been produced, allowing the engineers to lower the reservoir levels accordingly. The Vajont dam disaster therefore was largely due to human errors, despite having an apparent natural cause, and if some of these errors could have been prevented, then although the landslide would have been likely to still occur, preventions could have been put in place such as evacuation, that would have saved the lives of those 2000 villagers below the dam. The volume of debris from the landslide was enough to destroy the reservoir, although ironically the dam itself still survives, with little damage.