Val Pola landslide

In June–July 1987, Valtellina witnessed an exceptionally high rainfall accompanied with rapid glacier melting due to relatively high altitude of the 0 degree isotherm. As a result, the Val Pola Creek significantly eroded its valley flanks, including the area of debris accumulation of post-glacial landslides.[3] This resulted in a fracture which detached an estimated volume 35–45 million cubic metres of old debris from the Northern slope of the Mount Zandila (Eastern side of Pizzo Coppetto[5]) first detected on July 25. On July 26 evacuations of local villages started. The fracture eventually produced a rapid rock avalanche with subsequent shallow landslides of the Val Pola sides and a debris flow along the Val Pola thalweg.[6] The flow entrained estimated 5–8 million cubic meters of debris. The created alluvial fan dammed the Adda River and created a lake. The mass ran about 1.5 km downstream and generated an upstream mud wave 35m high which traveled about 2.7 km. [3]

Twenty-two people were killed by the main landslide, which created a huge wave in the temporary lake caused by a previous, smaller landslide.[6]

The landslide resulted in 35 m deepening of the Val Pola canyon.[6]

The debris from the Val Pola rock avalanche and landslide impounded on the Adda River creating a lake with 6 million cubic meters of water. The landslide itself obliterated 5 villages and six hamlets with 43 people died of various disaster-related causes.[7][2][8] The total cost of the disaster and several months of its mitigation was about 400 million euros.[9]

The resulting lake created the floodability threat, because the accumulated huge amount of water threatened to breach the debris dam and flood the Adda valley. Efforts to mitigate the threat included evacuation of about 25,000 people downstream, works to stabilize the debris tongue to prevent spill-over with subsequent dam breach, and works to drain the lake in controllable manner.[7][2][10]

The disaster coincided with the change of the government of Italy, including the replacement of the Minister of Civil Protection, which resulted in certain amount of policy vacuum and non-optimal decisions.[7]

In July 2007, a civil protection national exercise Valtellina 2007 was carried out which simulated hydraulic and hydrogeological risk similar to that of the 1987 disaster.[4]

Frana-Pizzo-Coppetto
Pizzo Coppetto - Alta Valtellina (Sondrio)
LocationAddaRiver
Adda River location

Coordinates: 46°22′44″N 10°20′24″E / 46.379°N 10.340°E The Val Pola landslide (Val Pola rock avalanche) happened in Valtellina, Lombardy, Northern Italian Alps, on July 28, 1987 and resulted in the Valtellina disaster (destruction of villages, road closure, flooding threat) with the total cost of 400 million euros. [1] [2] [3] The calamity affected the provinces of Sondrio, Brescia, Bergamo, Lecco, and Como.[4]

References

  1. ^ Costa, J. E.: Nature, mechanics, and mitigation of the Val Pola landslide, Valtellina, Italy, 1987–1988. Zeitschrift fur Geomorphologie 35, 15–38, 1991.
  2. ^ a b c Natural Disasters (1993) ISBN 1-85728-094-6, p. 364
  3. ^ a b c "Numerical modelling of large landslides stability and runout", Natural Hazards and Earth System Sciences (2003) 3: 523–538
  4. ^ a b "Vatellina 2007", a civil protection national exercise
  5. ^ "Vatellina 2007", a civil protection national exercise
  6. ^ a b c "Val Pola Rock avalanche of July 28, 1987"
  7. ^ a b c David Alexander, "Valtellina Landslide and Flood Emergency, Northern Italy, 1987", Disasters, 1988, vol. 12, issue 3, pp. 212–222 doi:10.1111/j.1467-7717.1988.tb00671.x
  8. ^ "Val Pola Rock avalanche of July 28, 1987"
  9. ^ "Numerical modelling of large landslides stability and runout", Natural Hazards and Earth System Sciences (2003) 3: 523–538
  10. ^ Costa, J. E.: Nature, mechanics, and mitigation of the Val Pola landslide, Valtellina, Italy, 1987–1988. Zeitschrift fur Geomorphologie 35, 15–38, 1991.
Adda (river)

The Adda (Latin Abdua, or Addua; in Lombard Ada or, again, Adda in local dialects where the double consonants are marked) is a river in North Italy, a tributary of the Po. It rises in the Alps near the border with Switzerland and flows through Lake Como. The Adda joins the Po a few kilometres upstream of Cremona. It is 313 kilometres (194 mi) long. The highest point of the drainage basin is the summit of la Spedla (a subpeak of Piz Bernina), at 4,020 metres (13,190 ft).

Towns along the river Adda include Bormio, Brivio, Tirano, Sondrio, Bellagio and Lecco (both on Lake Como), and Lodi.

Landslide

The term landslide or less frequently, landslip, refers to several forms of mass wasting that include a wide range of ground movements, such as rockfalls, deep-seated slope failures, mudflows, and debris flows. Landslides occur in a variety of environments, characterized by either steep or gentle slope gradients, from mountain ranges to coastal cliffs or even underwater, in which case they are called submarine landslides. Gravity is the primary driving force for a landslide to occur, but there are other factors affecting slope stability that produce specific conditions that make a slope prone to failure. In many cases, the landslide is triggered by a specific event (such as a heavy rainfall, an earthquake, a slope cut to build a road, and many others), although this is not always identifiable.

List of landslides

This list of landslides is a list of notable landslides and mudflows divided into sections by date and type. This list is very incomplete as there is no central catalogue for landslides, although some for individual countries/areas do exist. Volumes of landslides are recorded in the scientific literature using cubic kilometres (km3) for the largest and millions of cubic metres (normally given the non-standard shortening of MCM) for most events.

Permafrost

In geology, permafrost is ground, including rock or (cryotic) soil, with a temperature that remains at or below the freezing point of water 0 °C (32 °F) for two or more years. Most permafrost is located in high latitudes (in and around the Arctic and Antarctic regions), but at lower latitudes alpine permafrost occurs at higher elevations. Ground ice is not always present, as may be in the case of non-porous bedrock, but it frequently occurs and it may be in amounts exceeding the potential hydraulic saturation of the ground material. Permafrost accounts for 0.022% of total water on Earth and the permafrost region covers 24% of exposed land in the Northern Hemisphere. It also occurs subsea on the continental shelves of the continents surrounding the Arctic Ocean, portions of which were exposed during the last glacial period.The thawing of permafrost has implications for the global climate. A global temperature rise of 1.5 °C (2.7 °F) above current levels would be enough to start the thawing of permafrost in Siberia, according to one group of scientists.

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