Valtellina disaster

The Valtellina disaster happened in Valtellina, Northern Italian Alps, in July-August 1987. The calamity affected the provinces of Sondrio, Brescia, Bergamo, Lecco, and Como.

The disaster started from a series of meteo-hydrological events known as the "Valtellina Flood" ( _it. Alluvione della Valtellina”) which severely affected Valtellina in the second half of July. It involved heavy rainfall and glacier melting. This resulted in flooding of various rivers and creeks which impacted many villages and towns. The resulting softening of the soil destabilized accumulations of debris from pre-glacial landslides on Northern slope of the Mount Zandila (Eastern side of Pizzo Coppetto) and triggered the high-velocity Val Pola landslide. [http://valtellina.protezionecivile.regione.lombardia.it/.../documentoimpianto_esercitazione_en.pdf "Vatellina 2007"] , a civil protection national exercise ]

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. 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] "Natural Disasters" (1993) ISBN 1857280946, [http://books.google.com/books?id=FJki-cMoiwAC&pg=PT386&lpg=PT386&dq=valtellina+disaster&source=web&ots=t4NhiznN6-&sig=gmY257ypiHwDBZxVEwzUY5-7FLU&hl=en p. 364] ] [ [http://books.google.com/books?id=bxscy9clAToC&pg=PA71&lpg=PA71&dq=%22val+pola%22&source=web&ots=uSq1uBlpHu&sig=w3TTxTkJNc-5_px404uRO_v8PV0&hl=en "Val Pola Rock avalanche of July 28, 1987"] ] The total cost of the disaster and several months of its mitigation was about 400 million euros. [ [http://www.nat-hazards-earth-syst-sci.net/3/523/2003/nhess-3-523-2003.pdf. "Numerical modelling of large landslides stability and runout"] , "Natural Hazards and Earth System Sciences" (2003) 3: 523–538]

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. [Costa, J. E.: Nature, mechanics, and mitigation of the Val Pola landslide, Valtellina, Italy, 1987–1988. Zeitschrift fur Geomorphologie 35, 15–38, 1991.]

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

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.

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