The Val Pola landslide (Val Pola rock avalanche) happened in

Valtellina Valtellina or the Valtelline (occasionally spelled as two words in English: Val Telline; rm, Vuclina (); lmo, Valtelina or ; german: Veltlin; it, Valtellina) is a valley in the Lombardy region of northern Italy, bordering Switzerland. Toda ...

Lombardy Lombardy ( it, Lombardia, Lombard language, Lombard: ''Lombardia'' or ''Lumbardia' '') is an administrative regions of Italy, region of Italy that covers ; it is located in the northern-central part of the country and has a population of about 10 ...

, Northern

Italian Alps The Alps () ; german: Alpen ; it, Alpi ; rm, Alps ; sl, Alpe . are the highest and most extensive mountain range system that lies entirely in Europe, stretching approximately across seven Alpine countries (from west to east): France, Swi ...

, on July 28, 1987 and resulted in the Valtellina disaster (destruction of villages, road closure, and

flooding A flood is an overflow of water ( or rarely other fluids) that submerges land that is usually dry. In the sense of "flowing water", the word may also be applied to the inflow of the tide. Floods are an area of study of the discipline hydrolog ...

threat) with a total cost of 400 million

euro The euro ( symbol: €; code: EUR) is the official currency of 19 out of the member states of the European Union (EU). This group of states is known as the eurozone or, officially, the euro area, and includes about 340 million citizens . ...

s. Costa, J. E.: Nature, mechanics, and mitigation of the Val Pola landslide, Valtellina, Italy, 1987–1988. Zeitschrift fur Geomorphologie 35, 15–38, 1991.''Natural Disasters'' (1993)
p. 364
"Numerical modelling of large landslides stability and runout"
'' Natural Hazards and Earth System Sciences'' (2003) 3: 523–538 The calamity affected the provinces of

Sondrio Sondrio (; lmo, Sùndri; rm, Sunder; archaic german: Sünders or ; la, Sundrium) is an Italian city and ''comune'' and Provincial Capital located in the heart of the Valtellina. , Sondrio counts approximately 21,876 inhabitants (2015) and it is ...

Brescia Brescia (, locally ; lmo, link=no, label= Lombard, Brèsa ; lat, Brixia; vec, Bressa) is a city and ''comune'' in the region of Lombardy, Northern Italy. It is situated at the foot of the Alps, a few kilometers from the lakes Garda and Iseo. ...

Bergamo Bergamo (; lmo, Bèrghem ; from the proto- Germanic elements *''berg +*heim'', the "mountain home") is a city in the alpine Lombardy region of northern Italy, approximately northeast of Milan, and about from Switzerland, the alpine lakes Como ...

Lecco Lecco (, , ; lmo, label=Lecchese, Lècch ) is a city of 48,131 inhabitants in Lombardy, northern Italy, north of Milan. It lies at the end of the south-eastern branch of Lake Como (the branch is named ''Branch of Lecco'' / ''Ramo di Lecco''). ...

, and

Como Como (, ; lmo, Còmm, label=Comasco dialect, Comasco , or ; lat, Novum Comum; rm, Com; french: Côme) is a city and ''comune'' in Lombardy, Italy. It is the administrative capital of the Province of Como. Its proximity to Lake Como and ...

. During June and July 1987 Valtellina witnessed an exceptionally high

rainfall Rain is water droplets that have condensed from atmospheric water vapor and then fall under gravity. Rain is a major component of the water cycle and is responsible for depositing most of the fresh water on the Earth. It provides water f ...

accompanied with rapid

glacier A glacier (; ) is a persistent body of dense ice that is constantly moving under its own weight. A glacier forms where the accumulation of snow exceeds its Ablation#Glaciology, ablation over many years, often Century, centuries. It acquires dis ...

melting due to the 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. This resulted in a fracture which detached an estimated volume of 35–45 million cubic metres of old debris from the Northern slope of the Mount Zandila (Eastern side of Pizzo Coppetto) first detected on July 25. On July 26 evacuations of local villages started. The fracture eventually produced a rapid

rock avalanche A rockslide is a type of landslide caused by rock failure in which part of the bedding plane of failure passes through compacted rock and material collapses ''en masse'' and not in individual blocks. Note that a rockslide is similar to an avalan ...

with subsequent shallow landslides of the Val Pola sides and a

debris flow Debris flows are geological phenomena in which water-laden masses of soil and fragmented rock rush down mountainsides, funnel into stream channels, entrain objects in their paths, and form thick, muddy deposits on valley floors. They generally ...

along the Val Pola

thalweg In geography and fluvial geomorphology, a thalweg or talweg () is the line of lowest elevation within a valley or watercourse. Under international law, a thalweg is the middle of the primary navigable channel of a waterway that defines the bounda ...

. The flow entrained an estimated 5–8 million cubic meters of debris. The created

alluvial fan An alluvial fan is an accumulation of sediments that fans outwards from a concentrated source of sediments, such as a narrow canyon emerging from an escarpment. They are characteristic of mountainous terrain in arid to semiarid climates, but a ...

dammed the

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 created a lake. The mass ran about 1.5 km downstream and generated an upstream mud wave 35 m high which traveled about 2.7 km. Twenty-two people were killed by the main landslide, which created a huge wave in the temporary lake caused by a previous, smaller landslide."Val Pola Rock avalanche of July 28, 1987"
/ref> The landslide resulted in a 35 m deepening of the Val Pola canyon. The debris from the Val Pola

and

landslide Landslides, also known as landslips, are several forms of mass wasting that may include a wide range of ground movements, such as rockfalls, deep-seated grade (slope), slope failures, mudflows, and debris flows. Landslides occur in a variety of ...

impounded on the

creating a lake with 6 million cubic meters of water. The landslide itself obliterated 5 villages and six hamlets with 43 people dying of various disaster-related causes.David Alexander, "Valtellina Landslide and Flood Emergency, Northern Italy, 1987", ''

Disasters A disaster is a serious problem occurring over a short or long period of time that causes widespread human, material, economic or environmental loss which exceeds the ability of the affected community or society to cope using its own resources ...

'', 1988, vol. 12, issue 3, pp. 212–222 The total cost of the disaster and several months of its mitigation was about 400 million

s. The resulting lake created the floodability threat, because the accumulated huge amount of water threatened to breach the debris

dam A dam is a barrier that stops or restricts the flow of surface water or underground streams. Reservoirs created by dams not only suppress floods but also provide water for activities such as irrigation, human consumption, industrial use ...

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 a controllable manner. The disaster coincided with the change of the

government of Italy The government of Italy is in the form of a democratic republic, and was established by a constitution in 1948. It consists of legislative, executive, and judicial subdivisions, as well as a Head of State, or President. The Italian Constitutio ...

, including the replacement of the Minister of Civil Protection, which resulted in a certain amount of policy vacuum and non-optimal decisions. By appointment of the Ministry of Civil Protection, a large monitoring system was installed on many different sites throughout the Valtellina, to check the progress of the landslide phenomena. In July 2007, a

civil protection Civil defense ( en, region=gb, civil defence) or civil protection is an effort to protect the citizens of a state (generally non-combatants) from man-made and natural disasters. It uses the principles of emergency operations: prevention, miti ...

national exercise, ''Valtellina 2007,'' was carried out which simulated hydraulic and hydrogeological risk similar to that of the 1987 disaster. "Vatellina 2007"
a civil protection national exercise

In Italian

The corresponding article in the Italian language can be found here: https://it.wikipedia.org/wiki/Alluvione_della_Valtellina_del_1987

References

{{reflist, 2 Landslides in Italy 1987 in Italy Landslides in 1987 Floods in Italy Province of Sondrio Province of Brescia Province of Bergamo Province of Lecco Province of Como History of Lombardy July 1987 events in Europe