Acqua alta

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St. Mark's Square at high tide , painting by Vincenzo Chilone , around 1825
St. Mark's Square, December 28, 1996
Venice, Acqua alta, 2005
Bridge construction during floods in late summer 2009

Audio file / audio sample Acqua alta ? / i (Italian forhigh water) is the annualwinter floodinVenice. It occurs whentheSciroccopushesthe water inland into theVenice lagoonwhen thetide isparticularly strongand the air pressure is low. Dependingonthetide, it lasts for several hours.

Annual phenomenon

At normal tide, the water level rises up to 90 cm above normal. There will be no flooding. If it rises higher, it is “Acqua alta”. The "Acqua-alta" season typically runs from September to April, and occasionally beyond. Its peak is around November.

  • 100 cm: only small parts of the city are flooded; at the lowest point of the city, St. Mark's Square , the water is then about 20 cm high.
  • 110 cm: An alarm is called, around 10% of the city is under water
  • 125 cm: About half the city is affected by the flood
  • 140 cm: a state of emergency is declared, 90% of the city is flooded

On November 4, 1966, the record water level of 194 cm put almost all of Venice under water.

Other causes

In the 1960s, the danger was exacerbated by the fact that Venice had quickly sunk by several centimeters due to the extraction of groundwater.

In the last few years the number of “acquire old” has noticeably increased. The Mayor of Venice attributes this to climate change .

Warning system

Until 2007, a simple siren system warned of floods. A differentiated signaling system has been in operation since December 2007. Depending on the expected water level, a siren tone can be heard several times from a total of eight sirens in the city area. At a height of 110 cm above normal, one hears a single tone, at 120 with a higher one, at 130 with two higher tones and at 140 cm with three higher tones.

The current Acqua alta forecast for the next few days can be found on the website of the tide forecast office operated by the Municipality of Venice (Italian Centro Previsioni e Segnalazioni Maree ).

Special flood situations

List of exceptional acquires from 1923 onwards

A total of over 300 Acque Alte with a height of at least 110 cm have been recorded since 1872. The data collected for 1872-1922 came from various sources. Since 1923 the data has been uniformly recorded by the municipal office for tide forecasting.

List of Acque old from a height of 140 cm since 1923:

  • 194 cm on November 4, 1966
  • 187 cm on November 12, 2019
  • 166 cm on December 22, 1979
  • 158 cm on February 1, 1986
  • 156 cm on October 29, 2018
  • 156 cm on December 1, 2008
  • 154 cm on November 15, 2019
  • 151 cm on November 12, 1951
  • 150 cm on November 17, 2019
  • 149 cm on November 11, 2012
  • 148 cm on October 29, 2018
  • 147 cm on April 16, 1936
  • 147 cm on November 16, 2002
  • 145 cm on October 15, 1960
  • 145 cm on December 25, 2009
  • 144 cm on November 3rd, 1968
  • 144 cm on November 6, 2000
  • 144 cm on December 23, 2009
  • 144 cm on December 24, 2010
  • 144 cm on November 13, 2019
  • 144 cm on December 23, 2019
  • 143 cm on November 1st, 2012
  • 143 cm on February 12, 2013
  • 142 cm on December 8, 1992
  • 140 cm on February 17, 1979

Acqua alta in November 2019

Campo Erberia (northwest of the Rialto Bridge) on November 14, 2019

On November 12, 2019, shortly before midnight, the level rose to 187 cm above sea ​​level . Triggered by tidal waves driven by the wind from the south on the full moon on November 12th , the flood remained longer due to the weather conditions (low Detlef); the flood then flowed off and on Friday, November 15, again reached high values ​​of 154 cm, with 80 percent being flooded by Venice and the incumbent government of Italy declaring the urban area a state of emergency. In addition to the old town of Venice - as in 1966 - the neighboring islands of Pellestrina and, to a lesser extent, Burano were also affected by the flood. Driven by the foothills of the Ingmar Mediterranean low, St. Mark's Square reached another high water peak at 150 cm above normal on November 17th, at the same time as storms in Italy and snowfalls with the risk of avalanches on the southern edge of the Alps.

Ingress of salt water combined with water damage is one of the secondary problems. As a result of the rising damp, restorers also expect efflorescence from crystallizing salt on frescoes of the world cultural heritage and on masonry.

Protective measures

As a flood protection measure, the MO.SE project is to be implemented with a planned completion in 2021.

reception

The crime novel Donna Leon - Acqua Alta by Donna Leon is set in Venice during the flood. It was filmed under the same title .

In 2016, in memory of the floods of 1966, the opera Aquagranda by the composer Filippo Perocco was premiered in the Teatro La Fenice .

Trade fair for flood protection

Next is Acqua alta the name of the annually held international trade fair for flood control , climate change impacts and disaster management . It took place for the first time in 2003 at the Munich exhibition center and was also held there in 2005. In 2006 it moved to the CCH - Congress Center Hamburg and took place there again in 2008. Since then, it has been held every two years with the alpine version, the Acqua alta alpina , which took place in Salzburg for the first time in 2007 . The trade fair has been held in Essen since November 2014 . There is also an Acqua Alta in Singapore , which deals with coastal protection in the tsunami areas .

Web links

Commons : Floods in Venice  - Collection of images, videos and audio files

Individual evidence

  1. https://www.bbc.com/news/world-europe-50401308
  2. Le sirene di allertamento (approfondimento), Città di Venezia
  3. ^ Institution Centro Previsioni e Segnalazioni Maree
  4. Grafici e statistiche. In: comune.venezia.it. Retrieved November 18, 2019 (Italian).
  5. Highest level since 1966 - record flood in Venice. In: srf.ch . November 13, 2019, accessed November 13, 2019 .
  6. Acqua alta: le isole avamposti dei disastri (Italian), Metropolitano.it, November 13, 2019.
  7. Record flood: Third tidal wave hit Venice , ch. wetter.com , November 17, 2019.
  8. Italy declares state of emergency to respond to Venice flooding (English), The Telegraph, November 14, 2019.
  9. Floods in Venice: Salts threaten paintings and frescoes , Interview with the restorer Sven Taubert, Deutsche Welle, November 14, 2019.