The Valtellina disaster happened in Valtellina

Valtellina

Valtellina or the Valtelline valley ; is a valley in the Lombardy region of northern Italy, bordering Switzerland. Today it is known for its skiing, its hot spring spas, its cheeses and its wines...

, Northern Italian Alps, in July-August 1987. The calamity affected the provinces of Sondrio

Sondrio

Sondrio is an Italian town and comune located in the heart of the Valtellina. Sondrio counts approximately 22,000 inhabitants and it is the administrative centre for the Lombard Province of Sondrio.- History :...

, Brescia

Brescia

Brescia is a city and comune in the region of Lombardy in northern Italy. It is situated at the foot of the Alps, between the Mella and the Naviglio, with a population of around 197,000. It is the second largest city in Lombardy, after the capital, Milan...

, Bergamo

Bergamo

Bergamo is a town and comune in Lombardy, Italy, about 40 km northeast of Milan. The comune is home to over 120,000 inhabitants. It is served by the Orio al Serio Airport, which also serves the Province of Bergamo, and to a lesser extent the metropolitan area of Milan...

, Lecco

Lecco

Lecco is a town of c. 47,760 inhabitants in Lombardy, northern Italy, north of Milan, the capital of the province of Lecco. It lies at the end of the south-eastern branch of Lake Como...

, and Como

Como

Como is a city and comune in Lombardy, Italy.It is the administrative capital of the Province of Como....

.

The disaster started from a series of meteo-hydrological events known as the "Valtellina Flood" which severely affected Valtellina in the second half of July. It involved heavy rainfall and glacier

Glacier

A glacier is a large persistent body of ice that forms where the accumulation of snow exceeds its ablation over many years, often centuries. At least 0.1 km² in area and 50 m thick, but often much larger, a glacier slowly deforms and flows due to stresses induced by its weight...

 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

Val Pola landslide

The Val Pola landslide happened in Valtellina, Lombardy, Northern Italian Alps, on July 28, 1987 and resulted in the Valtellina disaster with the total cost of 400 million euros...

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The debris from the Val Pola rock avalanche and landslide

Landslide

A landslide or landslip is a geological phenomenon which includes a wide range of ground movement, such as rockfalls, deep failure of slopes and shallow debris flows, which can occur in offshore, coastal and onshore environments...

 impounded on the Adda River

Adda River

The Adda 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 long...

 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. The total cost of the disaster and several months of its mitigation was about 400 million euro

Euro

The euro is the official currency of the eurozone: 17 of the 27 member states of the European Union. It is also the currency used by the Institutions of the European Union. The eurozone consists of Austria, Belgium, Cyprus, Estonia, Finland, France, Germany, Greece, Ireland, Italy, Luxembourg,...

s.

The resulting lake created the floodability

Floodability

Floodability may refer to one of the following.*Floodability , a characteristic of the construction of a ship to resist flooding.*Floodability of powderized materials, its tendency to liquid-like flow due to natural fluidization of a mass of particles by air .*The risk of flooding of land areas or...

 threat, because the accumulated huge amount of water threatened to breach the debris dam

Dam

A dam is a barrier that impounds water or underground streams. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levees are used to manage or prevent water flow into specific land regions. Hydropower and pumped-storage hydroelectricity are...

 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.

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.