Sea Level in Venice Venice,

¶ … Sea Level in Venice

Venice, Italy is 1,300 years old and built on mudflats in the center of a lagoon. It tops the list of the world's most endangered cities, since high tides have become frequent (almost every two weeks), along with winter flooding. Known as acqua alta or "high water," these tides can flood the city with more than a meter of salt-water. Then visitors see water splashing out up the banks of the canals and flowing out of the drains in the Piazza San Marco. Yet the tourist trade is booming and the residents of the city are fleeing. Mirina Vio, 72, "complained that life in her native city had worsened considerably in recent years - higher prices, overcrowding, dirtier streets - as the tourism industry blossomed" (Povoledo, p. 1).

The flooding or acqua alta is sometimes thought of as proof that Venice is sinking into the sea. Sure, the city sank 10 cm in the last century, "because of industrial groundwater extraction," but the sinking stopped when engineers capped artesian wells on the mainland in the 1960s. Today, it is estimated that Venice is still sinking at the rate of 0.5 to 1 mm per year, because of its geology and the city's millions of pilings pressing into the land (Zwingle, p. 1).

But the biggest problem is the rising level of the sea, which becomes more of a threat as "global warming melts the arctic ice caps" (Imboden, 1). Over the last 100 years, flooding has increased from less than 10 times per year to more than 60 times per year. Acqua alta occurs when any two of the following coincide: A sirocco blowing in the Adriatic Sea, which makes water back up into the Lagoon, a substantial decrease in barometric pressure, and a high tide during the full or the new moon.

The phenomenon is most likely to take place between late September and April, and especially in the months of October, November, and December. By official definition, acqua alta occurs when the tide is 90 mm (3.54 inches) above normal high tide (Imboden, p. 2)

Not every part of the city is susceptible to the flooding, as the following chart indicates. Indeed, the depth of water in most streets is less than the "level of tide" indicated.

Level of tide

Conversion to Feet and Inches

Percentage of Venice flooded

Up to 80 cm

31.50 in.

Normal tide

39.43 in. (3 ft. 3 in.)

42.41 in. (31/2 ft.)

47.24 in (4 ft.)

51.18 in. (4 ft. 3 in.)

55.12 in. (4 ft. 7 in.)

On November 4, 1966, an extremely high level tide in the Venetian Lagoon brought the water to almost 6 feet above normal, approximately up to chest height for anyone who might be in the Piazza San Marco, the lowest point in the city. For eight hours a strong southeast wind kept the normal tide at bay. Those who experienced this exceptionally high tide vowed it should never happen again. However, ever since 1966, almost all accounts of high water, even 3 inches, are considered evidence of doom and disaster (Zwingle, p. 1).

Again, in October of 2004, 80% of Venice flooded when the water came up to 135 cm. The Piazza San Marco was inundated with 16 inches of water in the worst flooding in the last ten years. But there have been nine floods almost as bad as this one since the record high in 1966.

The City of Venice, along with concerned international organizations, is working on solving the problem with floodgates in the Lagoon entrance, as well as raising the pavement in low-lying parts of the city. Much of the raising of pavement has been done, but unless water barriers are made permanent, turning the Lagoon into a fresh-water lake, nothing else can be done. The high water arrives about every two weeks and sometimes is higher than previous times. And some believe it is getting worse, all to the benefit of the tourist trade.

Today, tourists come to see this strange phenomenon. The tourist trade is thriving in this "sinking city." Tourists still slog around in the knee-high water with plastic bags taped to their legs or ride the gondolas through the few canals where low bridges allow for boats passing beneath them. Films of tourists visiting Venice on Youtube show them wearing either thigh-high fishing boots or colored plastic bags so they will not get their shoes and clothes wet in the high water. Films show a young woman standing near the corner of a building with water up to her calves, wearing tall rubber boots, while boats motor past her over a sea unbroken by sidewalks or anything else. People climb onto and scramble across cafe tables in a loggia in order to enter a building. There are scenes of the long, wooden risers between tourist sites where hundreds of visitors walk single file along the narrow planks on high water days.