Volcanoes and Volcanic Eruptions
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CASE STUDY VAIONT LANDSLIDE, ITALY Monica Ghirotti1, Doug Stead2 1 Alma Mater-University of Bologna, Bologna, Italy 2 Simon Fraser University, Burnaby, BC, Canada
Synonyms Vajont landslide Definition The Vaiont landslide (northern Italy) is one of the best known and most tragic examples of a natural disaster induced by human activity. On October 9, 1963, a catastrophic landslide occurred on the northern slope of the Mount Toc; a rock mass of approximately 270 million m3 collapsed into the reservoir at velocities up to 30 m/s generating a wave that overtopped the dam and swept into the Piave valley below, with the loss of about 2,000 lives. Introduction Landslides, as major natural hazards, account for extremely significant property damage/losses in terms of direct/indirect costs, especially in hilly or mountainous areas. Triggering factors can be intensive rainfall, earthquake shaking, groundwater changes, or rapid stream erosion promoting a sudden decrease in the shear strength and stability of slope-forming materials. Landslides induced by reservoir impounding can also damage dams and result in considerable loss of life. The Vaiont reservoir landslide is one of the best-known examples of a natural disaster induced by human activity.
Many questions have been posed and remain concerning the legal, economic, social, and scientific issues associated with the history of the dam and in particular emergency management of the instability in the Vaiont reservoir slope up to the time of catastrophic failure. The global impact of the event has been to stimulate a large body of research on the stability of natural rock slopes and in particular the development of geotechnical risk protocols for the construction of hydroelectric projects in mountainous topography. The 1963 Vaiont rock slide represents a dramatic example of the consequences of limitations in available data (parameter uncertainty) and our understanding of slope failure processes (model uncertainty). It provides a clear example of the importance of fully understanding the complex mechanics and dynamics of large rock slope instabilities.
Chronology of events The Vaiont Dam, constructed between 1957 and 1960, is located on the Vaiont River in northern Italy, about 100 km north of Venice. The double-curved arch dam, at 265.5 m above the valley floor, was in 1963 the highest thin arch dam in the world. Its abutments were founded on the steep flanks of a deep canyon cut into dolomitic limestones of Malm and Dogger age. The planned full reservoir capacity was to reach a volume of 169 million m3. The slopes of Mount Toc underwent nearly 3 years of intermittent, slow slope movements, beginning at the time of the first filling of the reservoir. On October 9, 1963, at 22.39 local time, during the third reservoir emptying event, a catastrophic landslide (Figure 1) suddenly occurred on the southern slope of the Vaiont dam reservoir (northern slope of Mount Toc) and the whole mass collapsed into the reservoir in less than 45 s. The failed mass drove the water of the reserv
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