The Rising Tides of Venice
/During our week in Venice, we relaxed the worldschooling. We skipped math altogether and made the English assignment simply reading “Death at La Fenice” (which I read simultaneously so we could have a little book club). For social studies, Gabe has been studying the causes of the economic disparity between the north and south of Italy, which has mostly focused on the entrepreneurial stagnation in the south, so I thought it would be good to spend time on why Venice is such a rich city as a counterpoint—which means delving into it’s strategic position on trade routes as well as ingenuity in shipbuilding. This study got him very interested in Marco Polo and the Silk Road, which I’ve decided I’m obsessed with, so keep an eye out for how this impacts my own dreams. For science, I asked Gabe to focus on “The Physics of Venice”—how it was built and why it’s increasingly susceptible to water. You’ll find his final project below, which I think was at least partly inspired by our time rowing around the lagoon because while there, he had the image of being overtaken by a cruise ship and how that would flip his sense of scale.
The Rising Tides of Venice
The Floating City, The Queen of the Adriatic, La Serenissima. These are all affectionate terms for one of the engineering marvels of the world. From its open lagoon, to its narrow canals, Venice is a magical place. Of course, I’m not the only one who has realized this fact. In 1987, Venice was named a Unesco World Heritage Site, causing a massive influx in tourism. Since then there have been movies shot in Venice, celebrities have stayed in the city's lavish hotels along the Grand Canal, and many shops geared towards tourists have popped up. Obviously Venice was a popular attraction decades before the nomination, but not to the degree it is now. However, there are some major problems with this incredibly lucrative industry. It causes many “day trippers,” or tourists who visit for no more than eight hours or so to crowd the city. Because of this, many tourist shops opened up, over-saturating an already crowded field. While walking on any main “calle,” or small street, one will notice that almost a quarter of all of these shops are tourist shops.
As tourists rush into the city to capture the obligatory gondola selfie, many Venetians leave. Many feel the city has become a museum that is mobbed with people during the daylight hours and completely emptied at night, save the residents going out for a drink.
However, the tourists that come from planes or cars aren't even the worst impact of tourism in the city. That title goes to the towering cruise ships that arrive daily in the lagoon. These 100,000 tonne behemoths dwarf the city whenever they arrive, which is quite often. On June 14th, the busiest cruise date of the year, an average of eight cruise ships dock in the lagoon throughout the day. In fact on June 14th 2019, 18,304 tourists poured out of these vessels, clogging the streets of the city.
It’s not only the tourists pouring from cruise ships that troubles the Venetians. They often complain about the vibrations that they feel every time a cruise ship arrives. It’s not their imagination these massive vessels actually shake the foundations of the buildings. Normally in a port town this would not be a problem, but in Venice the tremors have begun to dislodge the buildings. If left unchecked, these vessels could completely uproot the fragile houses. A plan is in action to reroute all cruise ships to the harbor of the mainland, which will take effect next year, but even then the amount of people that will be dismounting and taking water taxis and water buses will be enormous, as the average “vaporetto” can only hold around 200 people at a time.
The buildings are being dislodged by these ships because the entire city is held up by millions of tree trunks, called piles. These piles were driven into the ground, past the layers of silt, sand, and mud, and into the dry dirt beneath. For reference, roughly 100,000 piles were used to hold up the bell tower of San Marco, and more than a million for one of the largest churches, Santa Maria della Salute. These piles have lasted for a millenia and a half, only occasionally being replaced. One would think that these would certainly have rotted by now, but for rot to occur on wood there must be a supply of air, and as these piles are completely submerged, they do not rot. Another common misconception is that the piles would simply snap after centuries, but they are oak and larch, two strong woods, and through an extensive period of time so much silt has been thrown against the wood that the piles have become petrified.
When these cruise liners come through the lagoon, it upsets the natural movement of the silt, rocking it about brutally. This begins to uproot the piles themselves, or sinking them deeper as the previously dry dirt gets dislodged, causing the buildings to slowly sink into the water.
However an even greater problem for the city is climate change. The effects of climate change are numerous, but perhaps the most concerning to the city of Venice is the rising ocean levels. Two main factors lead to rising ocean levels, the first being thermal expansion. When an object is heated, its atoms begin to vibrate and separate from each other, causing the atoms themselves to spread apart. This is how a thermometer works, as the mercury is heated by the external temperature, it’s atoms spread apart, causing it to expand within the glass tube. Thermal expansion accounts for over 30% of sea levels rising. The other 70% is caused by melting ice flowing into the sea at rapid rates, below the antarctic circle and above the arctic circle. According to the NOAA “Scientists have determined that the global sea level has been steadily rising since 1900 at a rate of at least 0.04 to 0.1 inches per year.” This is very bad for Venice, especially because the city itself is sinking into the ground. When Venetians pumped water from the ground for their wells, it disrupted the already fragile layer of mud that the piles stood in (the government halted the pumping and resumed it on the mainland). In fact, the city has sunk an estimated 1.5 meters since it was built. These two factors are causing venice to slowly be engulfed in water.
To combat the rising tides, the Venetian government has created a system, nicknamed project MOSE (Modulo Sperimentale Elettromeccanico, or Experimental Electromechanical Module), that aims to halt the ebbing waters whenever there is an acqua alta (when the tide is at an exceptional peak, 130 centimeters above sea level). The MOSE are, in essence, floodgates that protect the laguna from sudden surges of water. The “MOSE'' are individual barriers that are pneumatically raised when acqua alta is predicted. Once they are all raised, the water will have a harder time passing into the lagoon and flooding it. Mechanically speaking, they take more than an hour to raise the full mile of individual apparati. The Venetian government also must get authorization from Rome to raise the MOSE, again taking more time. Due to these extensive waits, the last time meteorologists predicted acqua alta, the Venetian government couldn’t act fast enough and the water flooded the city despite the MOSE. Another issue with these MOSE is that when they were designed they weren’t ready to handle the exponential growth in sea levels, water is expected to consistently breach the MOSE in the next 100-150 years.
Venice is a marvelous city, with beautiful sights to see around every corner. But for how much longer? With all of these detriments to the city, how much longer will the city be in its state of glory? How much longer will the city even be above water? This is not to say that you shouldn’t visit Venice, but be mindful of the impact you could have on the city, and while you’re there, make environmentally conscientious choices. Don’t litter in the canals or in the streets, try to use reusable water bottles, do whatever you can to keep this beautiful city alive. If you do want to visit Venice, do so in a way that doesn’t detriment the city. Arrive by any form of transportation other than cruise ships, as they contribute to the city sinking. When you are there, you can stimulate the local economy by purchasing from local shops, supporting the stores being taken over by tourist shops. If you have the ability, stay for more than just a day. Not only will you contribute to the economy, but you’ll get so much more out of it as you begin to see what’s below the surface of the city.
