Essay Sample on Vajont Dam: World's Tallest Dam in Northern Italy

Introduction

Vajont Dam is located in the Valley of Vajont River on the valleys of Monte Toc, Erto and Casso municipality in the northern Venice in Italy. The dam construction of the dam began in 1956 and was completed in 1960 on a steep and narrow limestone canyon. Vajont Dam remains the tallest dams in the world with a height of 860 ft. 520 ft. in length and a base of 27 Meters (89 ft.). The reservoir was designed as part of an extension of dams for use in hydropower generation by SADE (Societa Adriatica di Elettricita) [1]. On 9th October 1963, a massive landslide occurred at the reservoir, consisting of forest, earth and rock materials that significantly covered the reservoir, displacing huge amounts of water causing death and destruction of property in the nearby villages of Longarone, Pirago, Villanova, Rivalta and Fae [1]. The Italian government, who by the time of the accident owned the dam attributed the flooding disaster to the unpredicted and inevitable natural occurrence. The tragedy is both natural and man-made.

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Initial Warnings

The construction of Vajont Dam started in 1967 while it began filling in 1960. Initially, there were differing opinions regarding the safety of constructing the dam along Mount Toc, since there were ancient rockslides in the area. In November 1960, a rockslide occurred when the water level at the reservoir was a depth of 600 feet [2]. About 1 million cubic yards of rockslide resulted in a 7 ft. wave in the reservoir, however, there were no damages experienced. As a result, the water level was lowered from 600 feet to 450 feet through the construction of exploration wells and hydraulic models to monitor the dam's condition [1]. Moreover, a bypass tunnel was constructed to join the upper and lower sections of the reservoir in case of occurrence of another rockslide.

The reservoir resumed filling until November 1962, large precipitation that raised water levels to 780 feet, however, the levels were lowered in between December 1962 and March 1963 due to increasing earth movements within the basin of about 0.5 inches every day [2]. A risky pattern emerged when a 16 feet height was added to the reservoir in July 1963 when earth movement reoccurred of about 0.2 inches every day [1]. When water levels increased, the movements also increased in size, indicating a sign of disaster.

Through a model based experiment, SADE engineers reported a further risk of another landslide into the reservoir and they tried to control the landslides by monitoring water levels. When the basin was almost completely filled, movements were rampant within the area that worried the population. On October 9, 1963, a massive landslide occurred.

Destruction

Vajont Dam flood is considered as the most catastrophic rockslide in Europe because of the strong earth tremors that were felt up to Brussels. Moreover, the disastrous rockslide resulted in strong winds caused by the updraft of air and heavy flooding at the downstream. Very deep and high speed water caused a unique scale of fatalities. About 2056 people died with several injured, presenting minimal chances of rescue since the disaster occurred at night [3]. Majority of the survivors had lost all family members as well as their property. Structured within the area was either entirely destroyed or buried. At the time the rockslide occurred, their technical personnel at the site monitoring the dam, all who perished. Towns including Longarone, Pirago, Rivalta, Villanova, and Fae, which were located at the downstream were completely destroyed because of the high speed of the water. About 1,269 fatalities occurred at Longarone which was a well-known tourist destination, consisting of commercial and residential houses [2]. However, Vajont Dam was not significantly damaged although there was a combination of forces from the slide and the wave, hence it is still in existence though without water. Only the top section of the dam was damaged, indicating it was well designed.

Was Vajont Dam Flood A Preventable Disaster?

Before the construction of the dam, geologists studied the slope of Mount Toc and they learned of a shear zone that comprised of crushed rocks were seen during the construction of a tunnel. Geologists such as Eduardo Semenza cautioned of deep-seated landslides and smaller landslides that would compromise the functionality of the dam [3]. The small slides that occurred after completion of the dam in 1960 were anticipated. Based on the reservoir model, calculations done indicated a small landslide into the lake could produce a thirty meters high wave and an optimum water level of 700 meters was proposed, which was surpassed in 1963 by 10 meters [4].

There was a constant rejection of the worst scenario happening to the dam, despite early landslides, nobody faced up to abandon the whole project since it was pivotal to the economy, providing power to the nearby cities. There was little understanding of the large mass movements during the time by the electric company and authorities responsible for running the dam. Only a few professionals imagined that a whole mountain can collapse. Although there were conflicting interests in the project, engineers and geologists did not recognize the magnitude of the danger of such a huge landslide [5]. Past data is used to try and predict the future while standardizing observations. Complete removal of the dam or relocation of the population was the primary option with no other remediation option after the construction of the dam.

The government of Italy moved the survivors to newly built homes to the southeast and strongly discouraged those who wanted to return to mountain life. The government utilized the Vajont Dam flood disaster to stimulate the north-eastern part towards industrialization. A pumping station was set up at the basin of the dam to maintain the water levels at the lake constant. Moreover, a bypass gallery was extended beyond the dam to allow water to flow towards the Piave valley. However, the walls of the dam are still existing, it is not exploited and the dry basin is unrestricted for tourists. Vajont Dam flood was studied in the 2008 documentary series on a disaster of the century and UNESCO named it a "cautionary tale" make happen by "letdown by geologists and engineers".

Conclusion

A key takes away is that dam incidences and failures are primarily attributed to human-related errors. Public safety should be upheld while constructing dams. While previous risks of rockslides and their impacts were normalized, no clear warning messages were issued, endangering the life of the community around the dam. Very deep and high speed water caused a unique scale of fatalities. About 2056 people died with several injured, giving minimal chances of rescue since the disaster occurred at night.

References

[1] P. Paronuzzi and A. Bolla, "The prehistoric Vajont rockslide: An updated geological model", Geomorphology, vol. 169-170, pp. 165-191, 2012. Available: 10.1016/j.geomorph.2012.04.021. [1]L.

[2] G. Dangelo, M. Paolini, G. Vacis, T. Simpson, and Vajont, "The Story of Vajont," World History Today, vol. 75, no. 3/4, p. 208, 2001. Available: 10.2307/40156942.

[3] L. Superchi, M. Floris, M. Ghirotti, R. Genevois, M. Jaboyedoff, and D. Stead, "Technical Note: Implementation of a geodatabase of published and unpublished data on the catastrophic Vaiont landslide", Natural Hazards and Earth System Science, vol. 10, no. 4, pp. 865-873, 2010. Available: 10.5194/nhess-10-865-2010.

[4] B. Voight and C. Faust, "Frictional heat and strength loss in some rapid landslides: error correction and affirmation of mechanism for the Vaiont landslide", Geotechnique, vol. 42, no. 4, pp. 641-643, 1992. Available: 10.1680/geot.1992.42.4.641.

[5] D. Norbert, "Beyond failure: forensic case studies for civil engineers", Choice Reviews Online, vol. 46, no. 11, pp. 46-6218-46-6218, 2009. Available: 10.5860/choice.46-6218.