Last November Venice experienced the second highest tide in recorded history. Looking at the top 10 tides, we see that five have occurred in the past 20 years and the frequency of exceptional tidal flooding above 110 cm have ramped up dramatically through the years.
What are the causes of this trend?
(a) sea level rise. Recorded satellite data shows that the sea level increases at a rate of 3.3 mm/year, resulting in about 6.6 cm rise over the last 20 years (credit: NASA –Global Climate Change – https://climate.nasa.gov/vital-signs/sea-level/). This rise is caused mainly by two factors, both related to global warming: the added water from melting ice and the expansion of seawater as it warms. While the latter has played the most prominent role so far, it is believed that the first will significantly speed up the rise in coming years owing to the melting of Antarctic and Greenland ice.
(b) sinking of Venice. Early industrial projects, such as the construction of offshore piers and the railroad bridge to the mainland, affected the sea floor in ways that made the city more vulnerable to sinking effects. Twentieth-century industry worsened the situation by pumping out massive amounts of groundwater from the aquifer beneath the lagoon. Currently, it is estimated that Venice is subsiding at a rate of 1 mm/year (credit: LiveScience – https://www.livescience.com/39979-venice-gradual-sinking-charted-by-satellites.html).
(c) other causes. Venetian flooding occurs during the concurrent presence of high tide and strong sirocco winds that blow north-eastwards from the open sea to the lagoon. One effect of the changing climate is that jet streams are more frequently meridional so increasing the chance of strong sirocco winds and thereby of flooding. Additionally, the excavation of channels in the lagoon such as the “canale dei petroli” is believed to have intensified the water inflow rate during high tides, refer e.g. to [1] for a more comprehensive presentation.
[1] “Sustainable Venice: Suggestions for the future”. Edited by Ignazio Musu, Springer Science and Business Media, B.V., 2001.
As I left my hotel in the morning, this was the first encounter I made: a man came out of a church and, without a moment’s hesitation, went plunging into the waters.
The MOSE
MOSE (Experimental Electromechanical Module) is an integrated system of gates designed to temporarily isolate the Venetian lagoon from the Adriatic sea when a flooding is forecast. The entire project has been marked by questionable designs, faulty executions and serious episodes of bribery. The project was begun in 1987 by the Ministry of Infrastructure. In 2002 the final design was presented and, on 3 April 2003, the “Comitatone” approved its implementation. At present – 33 years after its initial plan – the project is still unfinished and recent inspections have evidenced that the 156 hinges that connect the gates to their concrete housing are at high risk of structural failure due to marine corrosion. In 2014, 35 people, including Giorgio Orsoni, the Mayor of Venice, were arrested on corruption charges. So far, the uncompleted project has cost € 5.5 billion to the Italian population.
Venetian people have a reputation for being fatalist, which gives them the extra boost to deal with misfortunes. Soon after I started roaming the city I bumped into these two guys, they seemed not to give much attention to all what was happening around them.
The future
Scientists have hypothesized various scenarios for sea level rise. According to the most likely scenario, sea level will rise 1 meter by year 2100 and 0.5 meters by year 2060, while the worst-case scenario (judged unlikely) foresees a rise of 0.5 meters by 2040 and 2.5 meters by 2100 (credit: NOAA Climate.gov – https://www.climate.gov/news-features/understanding-climate/climate-change-global-sea-level). On the ground of these forecasts, in the following I want to share with you my personal vision on the Venetian lagoon and the MOSE based on my background in systems theory, a subject that I regularly teach at the University of Brescia and in various graduate courses worldwide in my academic profession. Let me start by observing that every system is a low-pass. This means that every system cuts frequencies above a certain range so that an input that oscillates above the cut-off frequency disappears in the output. For example, if we move up and down fast enough an end of an elastic, a mass appended at the other end barely moves. This is the principle by which MOSE works: tides sway above the cut-off frequency of the system formed by the lagoon and the MOSE so that the city of Venice gets shielded away from the effect of tides. On the other hand, it is essential to observe that the gates of MOSE do not form a water tight barrier and this implies that a rise in the average sea level, whose variability hovers around frequency zero, will raise the level in the lagoon even when the gates are closed. In other words, the MOSE is entirely unsuitable to face the sea level rise that will happen in future years. It appears that, after 33 years from its initial plan, we are striving to reanimate a patient that is rapidly getting unsuitable to counteract the new challenges posed by global warming.
The beautiful Palazzo dei Camerlenghi is known for leaning towards the Grand canal. Partially submerged by the high tide, it reminded me an old stranded steamer as a gondola went past it.
This photographic gallery
I traveled to Venice on two distinct trips, on 17-18 November 2019, following the record tide registered on 12 November, and again on 22 December 2019 to photograph the everyday of the Venetian life during high tide. The gallery “the last tide” contains the snapshots of those intense two and a half days.
I arrived to an empty piazza San Marco. That man walked past me carrying the luggage of two isolated Japanese tourists, then he turned his head towards the old statue, perhaps asking for a sign of agreement. I had the impression that statue returned a slight nod of his head.
About Marco Campi
Marco C. Campi is a photographer and an Italian academic. His scientific studies evolve around a mathematical approach to cognitive sciences in an attempt to tie the concepts of observation, knowledge and uncertainty. His photographic bent developed early on in his life when he began exploring the environment with his Canon AE1. His approach to photography signs a continuity with his scientific studies where single frames are snapshots of humanity and a camera becomes a means of exploration to unveil connections and diversities in the society.
It was kind of startling seeing those two guys working with their laptop in that uncomfortable situation.
During exceptional high tides, the municipality of Venice places elevated walkways for everyone to walk on. I saw that man coming close to the end of the elevated walkway, then he got scared as the policemen asked him to “undock” to let others go through.
This is the very first picture I took in early morning on my second trip to Venice. In the main city square, one single man braves his way on the walkway while the Christmas tree looms high, it’s festive season.
Activists of Extension Rebellion protesting against mismanagement of the city of Venice.
I met Gualtiero dell’Osto, a great artist who makes Venetian masks and a socially-committed man, by absolute chance when walking a Venetian calle. His creation the “urlo muto” represents the unheeded shout of the Venetians. In this image, the urlo muto looks horrified while looking at the rising waters in piazza San Marco.
That old lady stood in the high waters for hours, looking invisible to most of the busy crowed.
