L'Italo-Americano

L'Italo-Americano THURSDAY, NOVEMBER 29, 2018 www.italoamericano.org 4 A world without Venice: a nightmare more real than we think L as t mon th V enice suffered the fourth highest floods in its history. Water seeped up through the drains, over the canal sides and into the houses, businesses and hotels of the city. And few were s pared, w ith around 75% of streets awash. Not that it's a new phenomenon as Venice has been flooding for centuries. Artist Federico Moja even captured acqua alta in his painting of St Mark's Square dated 1853. So w ith flood barriers in place around the w orld in N ew Orleans, Amsterdam and Lon- don, what is it about the Italian city that still makes it so vulner- able and what is being done to protect it? S cattered over dozens of islands separated by canals and surrounded by water, Venice is known as the floating city. It sits at the center of a lagoon at the top of the Adriatic Sea and twice a day the tide hurries in bringing salt water to nourish the brack- ish ecology. It's a cycle that has pers is ted for millennia and which the original Venetians exploited expertly to build their wealth. First came fishing, then naval supremacy and finally Venice used its sea-faring exper- tise to dominate trade down to Istanbul and across to the Middle East. At a practical level, tides are also essential to bring nutrients to lagoon life and to flush out sewage and silt that builds up over time. Without tides the city of V enice may never have become rich and would soon silt up making canals impassable, transforming the marshes into mud banks, then dry land and running the floating city aground. Tides bring life to the lagoon in so many ways, but with the tides come dangers, too. For most of the year, tides calmly fluctuate from a low of around 30 centimeters to a high of 1 meter, refreshing the lagoon without infiltrating the streets or campi. On occasions, especially in January, the water even sinks lower during acqua bassa, leav- ing boats stranded in the mud at the bottom of the canals. And the lagoon marshes act as a buffer to protect the city by soaking up excessive water when tides go a little higher. But as Autumn merges into Winter, a series of seasonal and environmental fac- tors converge sending seawater over the thresholds of the city. First the astronomical align- ment of the sun and moon raise tides significantly as the normal gravitational pull is intensified, and higher waters flow into the lagoon. Meteorological changes bring an autumnal sirocco wind blowing from the southeast. The winds literally push seawater up the Adriatic, sending a surge in through the lagoon inlets and raising the tidal levels. And a third, natural geographic feature, forms the perfect storm. The long shape of the almost enclosed Adriatic causes the sea to oscillate or sway slowly back and forth. This produces a stand- ing wave that runs up and down the basin just like bathwater does when you get out. And it's when this swaying synchronizes with a high astronomical tide and siroc- co winds that serious acqua alta high tides occur flooding streets, shops, houses and hotels. A s tronomy, w eather and geography are not the only fac- tors contributing to Venice's ris- ing waters however. There are two more factors; one local and one global. Scientists first recognized a problem with local subsidence This November, 90 centimeters of water entered Saint Mark's Basilica: events like this could become more and more common if we don't act quickly on climate change © Federico Roiter ELIZABETH SALTHOUSE Continued to page 6 NEWS & FEATURES TOP STORIES PEOPLE EVENTS Venice under water: the flood that hit the city in recent weeks has been the fourth highest in its history © Federico Roiter

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