Alla Sella Zerbino

the concrete dam Alla Sella Zerbino (Diga dello Zerbino, Diga the molecular one, Sella Zerbino Dam) with Ovada in the Piemont in the Liguri Apenninen, province Alessandria /Italy broke to 13. August 1935 around 13:15 clock with a flood. The Flutwelle caused large damage in molecular ones and Ovada; there were 100 or more dead one.

the two concrete dams

the concrete dam was a curved gravity dam. She was built 1917-1923 and taken for 1924 in enterprise. The dam served the generation of current from water power and by the society “Officine Elettriche Genovesi” (O.E.G.) was operated. Pilot contents amounted to probably approx. 18 million m ³. The river Orba was accumulated to the Lago di Ortiglieto. Because of the land form in another place of the artificial lake, 500 m far away on the left bank, a second concrete dam was needed, after the height of the main concrete dam had been increased in relation to the original plan by 13 m. With the building there were geological problems with the building ground.

Data of the main rope wall Bric Zerbino (Diga di Bric Zerbino):

  • Height: 47 m
  • length: 70 m
  • radius of curvature: 200 m

data of the Nebenstaumauer Sella Zerbino (Diga secondaria di Sella Zerbino):

  • Height: 14 or 16 m
  • length: 110 m

the valleys behind the two check places unite behind the mountain Saccone, around which the Orba flows in a Mäander, again to the Orba valley.

the disaster

to 13. August rained it 364 mm in 8 hours in the catchment area of the Orba, at some places still more: in Lavagnina 554 mm (182 in 2 hours), in Pianpaludo 453 mm, in Masone 377 mm. In 24 hours 30% of the middle yearly precipitation fell. The discharge donation amounted to 15 m ³ per second per square kilometer. This resulted in a discharge of floodwater of 2200 - 2300 m ³ /s, a 1000-jähriges flood. The Bric Zerbino dam had however only one discharge capacity from 800 to 900 m ³ /s. Therefore the water level continued to rise always. Over 13:00 clock the situation critical and around 13:15 is broken the Nebenstaumauer Sella Zerbino.

The Flutwelle led approx. 18 million cubic meter water with itself. It destroyed first one hotel and the 3 km underneath convenient power station buildings. It arrived 15 minutes later at molecular ones. There it destroyed among other things 18 m high and 120 m is enough for bridge. Subsequently, the tides reached the city Ovada, those approx. northeast of molecular ones is appropriate for 3.5 km. The entire discharge quantity with the flood becomes estimated on 30 to 50 millions m ³. Altogether there were more than 100 dead ones.

The break happened only 12 years after the disaster of Gleno. The concrete dam Bric Zerbino stands this very day, is however not used.

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see also: Dam disasters


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