Editing Venice (section)

=== Subsidence ===
[[Subsidence]], the gradual lowering of the surface of Venice, has contributed – along with other factors – to the seasonal ''[[Acqua alta]]'' ("high water") when the city's lowest lying surfaces may be covered at high tide.

{{anchor|Foundations}}

==== Building foundations ====
Those fleeing barbarian invasions who found refuge on the sandy islands of Torcello, Iesolo, and Malamocco, in this coastal lagoon, learned to build by driving closely spaced [[Deep foundation|piles]] consisting of the trunks of [[alder]] trees, a wood noted for its water resistance, into the mud and sand,<ref>{{cite web |url=http://www.treesforlife.org.uk/forest/mythfolk/alder.html |title=Mythology and Folklore of the Alder |last=Kendall |first=Paul |date=25 August 2010 |website=[[Trees for Life (Scotland)|Trees for Life]] |access-date=6 August 2011 |url-status=dead |archive-url=https://web.archive.org/web/20110805135339/http://www.treesforlife.org.uk/forest/mythfolk/alder.html |archive-date=5 August 2011}}</ref><ref>{{cite web |url=http://www.cvni.org/treenursery/trees/alder |title=Alder – Alnus glutinosa |publisher=Conservation Volunteers Northern Ireland |access-date=6 August 2011}}</ref> until they reached a much harder layer of compressed [[clay]]. Building foundations rested on plates of [[Istrian stone|Istrian limestone]] placed on top of the piles.<ref>{{Cite book |last=Standish |first=Dominic |chapter=Barriers to barriers: why environmental precaution has delayed mobile floodgates to protect Venice |chapter-url=https://www.academia.edu/441655 |editor-last=Okonski |editor-first=Kendra |title=Adapt or die: the science, politics and economics of climate change |page=40 |year=2003 |location=London |publisher=Profile Books |isbn=978-1-86197-795-3 |access-date=28 November 2014}}</ref><ref>{{Cite web |last=Bressanin |first=Anna |date=2025-03-26 |title=Mud, water and wood: The system that kept a 1604-year-old city afloat |url=https://www.bbc.com/future/article/20250324-the-ancient-forest-that-supports-venice |access-date=2025-04-01 |website=[[BBC News]] |language=en-GB}}</ref>

==== Flooding ====
{{Update|part=section|date=February 2024|reason=[[MOSE]] information does not cover anything after 2020, such as the 2023 completion date moved to 2025}}

[[File:AcquaAlta1 12 2008 3.JPG|thumb|''[[Acqua alta]]'' ("high water") in Venice, 2008]]{{Main|Sea level rise in Venice}}
Between autumn and early spring, the city is often threatened by flood [[tide]]s pushing in from the [[Adriatic Sea|Adriatic]]. Six hundred years ago, Venetians protected themselves from land-based attacks by diverting all the major rivers flowing into the lagoon and thus preventing sediment from filling the area around the city.<ref>{{cite web |url=https://www.pbs.org/wgbh/nova/venice/sieg_nf.html |title=NOVA {{pipe}} Sinking City of Venice {{pipe}} Venice Under Siege (non-Flash) {{pipe}} PBS |website=PBS}}</ref> This created an ever-deeper lagoon environment. Additionally, the lowest part of Venice, [[St Mark's Basilica]], is only {{convert|64|cm|in}} above sea level, and one of the most flood-prone parts of the city.<ref>{{Cite web |last=Brown |first=Hannah |date=9 August 2021 |title=Venice floods: Watch tourists wade through knee-deep water |url=https://www.euronews.com/travel/2021/08/09/venice-is-flooding-again-watch-tourists-wade-through-knee-deep-water |access-date=15 November 2021 |website=[[euronews]] |language=en}}</ref>

In 1604, to defray the cost of flood relief, Venice introduced what could be considered the first example of a stamp tax.<ref>{{cite web |last1=Iwu |first1=Rita |title=Stamp Tax |url=https://www.ibtimes.com/terms/s/stamp-tax |website=[[International Business Times]] |access-date=26 October 2022 |language=en |date=19 May 2021}}</ref> When the revenue fell short of expectations in 1608, Venice introduced [[Postal stationery|paper]], with the superscription "AQ" and imprinted instructions, which was to be used for "letters to officials". At first, this was to be a temporary tax, but it remained in effect until the fall of the Republic in 1797. Shortly after the introduction of the tax, Spain produced similar paper for general taxation purposes, and the practice spread to other countries.

During the 20th century, when many [[artesian well]]s were sunk into the periphery of the lagoon to draw water for local industry, Venice began to [[subsidence|subside]]. It was realized that extraction of water from the [[aquifer]] was the cause. The sinking has slowed markedly since artesian wells were banned in the 1960s. However, the city is still threatened by more frequent low-level floods – the ''[[Acqua alta]]'', that rise to a height of several centimetres over its [[quay]]s – regularly following certain tides. In many old houses, staircases once used to unload goods are now flooded, rendering the former ground floor uninhabitable.{{citation needed|date=February 2020}}

Studies indicate that the city continues sinking at a relatively slow rate of 1–2{{nbsp}}mm per year;<ref>{{cite report |last1=Bock |first1=Y. |display-authors=etal |title=Recent Subsidence of the Venice Lagoon from Continuous GPS and Interferometric Synthetic Aperture Radar |url=http://sciences.blogs.liberation.fr/files/venise-senfonce.pdf |date=2012 |url-status=dead |archive-url=https://web.archive.org/web/20160304124453/http://sciences.blogs.liberation.fr/files/venise-senfonce.pdf |archive-date=4 March 2016 |access-date=23 April 2019}}</ref><ref>{{cite web |url=https://www.comune.venezia.it/it/content/la-subsidenza-e-leustatismo |title=La subsidenza e l'eustatismo |language=it, en |trans-title=Subsidence and eustatism |date=25 March 2022 |website=City of Venice |archive-url=https://web.archive.org/web/20230506212333/https://www.comune.venezia.it/it/content/la-subsidenza-e-leustatismo |archive-date=6 May 2023 |url-status=live}}</ref> therefore, the state of alert has not been revoked.

In May 2003, Italian Prime Minister [[Silvio Berlusconi]] inaugurated the [[MOSE Project]] ({{Langx|it|Modulo Sperimentale Elettromeccanico}}), an experimental model for evaluating the performance of hollow floatable gates, expected to be completed by the end of 2025;<ref>{{cite web |url=https://www.bbc.com/future/article/20220927-italys-plan-to-save-venice-from-sinking |title=Italy's plan to save Venice from sinking |website=BBC |last=Phelan |first=Joseph |date=28 September 2022 |access-date=30 September 2022}}</ref> the idea is to fix a series of 78 hollow [[pontoon (boat)|pontoons]] to the sea bed across the three entrances to the lagoon. When tides are predicted to rise above {{Convert|110|cm}}, the pontoons will be filled with air, causing them to float on lagoon side while hinged at sea floor on seaside, thus blocking the incoming water from the Adriatic Sea.<ref>{{cite web |title=MOSE Project, Venice, Venetian Lagoon |url=https://www.water-technology.net/projects/mose-project/ |date=2019 |website=Water Technology |access-date=3 April 2019}}</ref> This engineering work was due to be completed by 2018.<ref>{{cite news |title='Moses project' to secure future of Venice |url=https://www.telegraph.co.uk/news/worldnews/europe/italy/3629387/Moses-project-to-secure-future-of-Venice.html |archive-url=https://ghostarchive.org/archive/20220110/https://www.telegraph.co.uk/news/worldnews/europe/italy/3629387/Moses-project-to-secure-future-of-Venice.html |archive-date=10 January 2022 |url-access=subscription |url-status=live |date=11 January 2012 |location=London |work=The Daily Telegraph |access-date=11 January 2012}}{{cbignore}}</ref> A [[Reuters]] report stated that the MOSE Project attributed the delay to "corruption scandals".<ref>{{cite web |last=Bastianello |first=Riccardo |url=https://globalnews.ca/news/6161825/venice-italy-flooding-disaster/ |title=Venice mayor declares disaster as city hit with 2nd-highest tide in history |work=[[Global News]] |date=13 November 2019}}</ref> The project is not guaranteed to be successful and the cost has been very high, with as much as approximately €2&nbsp;billion of the cost lost to corruption.<ref name="NatgeoWorrall201610" />

According to a spokesman for the National Trust of Italy ([[Fondo Ambiente Italiano]]):<ref>{{cite web |last=Gerard-Sharp |first=Lisa |url=http://www.natgeotraveller.co.uk/destinations/europe/italy/is-venice-going-under/ |title=Is Venice going under? |date=16 August 2016 |website=National Geographic}}</ref>

<blockquote>
Mose is a pharaonic project that should have cost €800m [£675m] but will cost at least €7bn [£6bn]. If the barriers are closed at only 90 cm of high water, most of St Mark's will be flooded anyway; but if closed at very high levels only, then people will wonder at the logic of spending such sums on something that didn't solve the problem. And pressure will come from the cruise ships to keep the gates open.
</blockquote>

On 13 November 2019, Venice was flooded when waters peaked at {{convert|1.87|m|ft|0|abbr=on}}, the highest tide since 1966 (1.94 m).<ref>{{cite news |url=https://www.bbc.com/news/world-europe-50401308 |title=Venice floods: Climate change behind highest tide in 50 years, says mayor |agency=BBC |date=13 November 2019}}</ref> More than 80% of the city was covered by water, which damaged cultural heritage sites, including more than 50 churches, leading to tourists cancelling their visits.<ref name="BBC Flood">{{cite news |last1=Hill |first1=Jenny |title=Flooded Venice battles new tidal surge |url=https://www.bbc.com/news/world-europe-50430855 |access-date=17 November 2019 |agency=BBC |date=15 November 2019}}</ref><ref>{{cite news |last1=Harlan |first1=Chico |last2=Pitrelli |first2=Stefano |url=https://www.washingtonpost.com/world/europe/venice-partly-submerged-by-highest-tides-in-half-a-century/2019/11/13/fa36566e-05fa-11ea-8292-c46ee8cb3dce_story.html |title=Venice submerged by highest tides in half a century |newspaper=[[The Washington Post]] |date=13 November 2019}}</ref> The planned [[flood barrier]] would have prevented this incident according to various sources, including Marco Piana, the head of conservation at St Mark's Basilica.<ref name="GuardianGiuffrida201911">{{cite news |last=Giuffrida |first=Angela |title='An apocalypse happened': Venice counts cost of devastating floods |date=13 November 2019 |url=https://www.theguardian.com/world/2019/nov/13/an-apocalypse-happened-venice-counts-cost-of-devastating-floods |work=The Guardian |access-date=13 November 2019 |quote=Work began in 2003 but has been dogged by delays and myriad issues, including a corruption scandal that emerged in 2014. The Venice mayor, Luigi Brugnaro, promised on Wednesday that the flood barrier would be completed.}}</ref> The mayor promised that work on the flood barrier would continue,<ref>{{cite web |url=https://www.newsweek.com/venice-flooding-city-underwater-right-wing-mayor-climate-change-1471438 |title=Venice flooding sees more than 85 percent of city underwater as right-wing mayor blames climate change |last=Georgiou |first=Aristos |date=13 November 2019 |website=[[Newsweek]] |language=en |access-date=14 November 2019}}</ref><ref name="GuardianGiuffrida201911" /> and the Prime Minister announced that the government would be accelerating the project.<ref name="BBC Flood" />

The city's mayor, [[Luigi Brugnaro]], blamed the floods on [[climate change]]. The [[Palazzo Ferro Fini|chambers]] of the [[Regional Council of Veneto]] began to be flooded around 10 pm, two minutes after the council rejected a plan to combat global warming.<ref>{{cite news |last1=Mezzofiore |first1=Gianluca |title=Italian council is flooded immediately after rejecting measures on climate change |url=https://edition.cnn.com/2019/11/14/europe/veneto-council-climate-change-floods-trnd-intl-scli/index.html |access-date=17 November 2019 |agency=CNN |date=15 November 2019}}</ref> One of the effects of climate change is [[sea level rise]] which causes an increase in frequency and magnitude of floodings in the city.<ref>{{cite news |last1=Calma |first1=Justine |title=Venice's historic flooding blamed on human failure and climate change |url=https://www.theverge.com/2019/11/14/20963878/venice-high-tide-climate-change-flood-barrier-sea-levels |access-date=17 November 2019 |agency=[[The Verge]] |date=14 November 2019}}</ref> A ''[[Washington Post]]'' report provided a more thorough analysis:<ref>{{cite news |last1=Harlan |first1=Chico |last2=Pitrelli |first2=Stefano |url=https://www.washingtonpost.com/world/europe/venice-partly-submerged-by-highest-tides-in-half-a-century/2019/11/13/fa36566e-05fa-11ea-8292-c46ee8cb3dce_story.html |title=Venice submerged by highest tides in half a century |newspaper=[[The Washington Post]] |date=13 November 2019 |quote=The [increased flooding] is a trend that jibes with the extremization of climate", said Paolo Canestrelli, founder and former head of the municipality's Tide Monitoring and Forecast Centre. "If we look at the course of history, we have documents dating back to 1872, and we can see that these phenomena didn't used to exist.}}</ref><blockquote>"The sea level has been rising even more rapidly in Venice than in other parts of the world. At the same time, the city is sinking, the result of tectonic plates shifting below the Italian coast. Those factors together, along with the more frequent extreme weather events associated with climate change, contribute to floods."</blockquote>

[[Henk Ovink]], an expert on flooding, told [[CNN]] that, while environmental factors are part of the problem, "historic floods in Venice are not only a result of the climate crisis but poor infrastructure and mismanagement".<ref>{{cite news |url=https://www.cnn.com/videos/tv/2019/11/19/henk-ovink-amanpour-climate-crisis-water-venice-floods.cnn |title=Historic floods in Venice a 'man-made disaster' |date=11 July 2007 |work=CNN |access-date=19 November 2019}}</ref>

The government of Italy committed to providing 20&nbsp;million euros in funding to help the city repair the most urgent aspects although Brugnaro's estimate of the total damage was "hundreds of millions"<ref>{{cite news |url=https://www.cbc.ca/news/world/venice-flood-tide-st-mark-s-square-1.5360583 |title=Venice flooded again 3 days after near-record high tide |date=15 November 2019 |work=[[CBC News]] |access-date=16 November 2019 |quote=Venice's mayor said the damage is estimated at hundreds of millions of euros and blamed climate change for the "dramatic situation" in the historic city. He called for the speedy completion of the city's long-delayed Moses flood defence project.}}</ref> to at least 1&nbsp;billion euros.<ref>{{cite news |last1=Barry |first1=Colleen |title=St. Mark's Square in Venice Reopens After Flooding, but Water Remains High |url=https://time.com/5731019/st-marks-square-venice-reopens/ |archive-url=https://web.archive.org/web/20191116171420/https://time.com/5731019/st-marks-square-venice-reopens/ |url-status=dead |archive-date=16 November 2019 |access-date=17 November 2019 |agency=[[Time (magazine)|Time]] |date=16 November 2019}}</ref>

On 3 October 2020, the MOSE was activated for the first time in response to a predicted high tide event, preventing some of the low-lying parts of the city (in particular the Piazza San Marco) from being flooded.<ref>{{Cite news |last=Silvestri |first=Manuel |date=3 October 2020 |title=Mose flood barrier finally holds the waters back for fragile Venice |work=Reuters |url=https://www.reuters.com/article/us-italy-weather-venice/flood-barrier-successfully-protects-venice-from-high-tide-idUSKBN26O0AZ |access-date=3 October 2020}}</ref>