"History of Venice on the Water"

Lecture by Professor Randolph H. Guthrie
Chairman of Save Venice
January 22, 2001 at Sotheby's

Italy, as part of the African geologic plate, is moving north, diving under the European plate. This is why the Alps are rising. It is also why Venice is sinking - about an inch and a half a century. In the early years after the war, the problem was exacerbated by nearby industries pumping water from the deep aquifers under Venice. The city sank a foot into the emptied spaces, sinking many centuries' worth in two decades.

Because it is low, the city is more susceptible to high water. This can result from natural causes such as low local atmospheric pressure, high tide, a storm with a south wind pushing water north, heavy rain on the mainland, and the sessa (a rocking of water in the Adriatic like that in a bathtub). It also results from man-made causes such as deepening the entrance channels to the lagoon (allowing water to rush in faster) and reducing the size of the lagoon by putting up walls around it (blocking expansion into the flood plain), filling in parts of it for land reclamation, and enclosing parts of it with impermeable walls to make fish farms.

The result today is that Venice is often flooded. The Piazza San Marco is 28 inches above average water level. Average high tide, coming twice a day, is 26 inches. Thus, only a slightly higher-than-normal tide floods the piazza. High tides reach 32 inches 100 times a year, flooding the piazza to a depth of 4 inches. You cannot walk in four inches of water without taking off your shoes and socks and rolling up your pants. You also cannot see what your bare feet are walking on. There is broken glass. There are dog and pigeon contributions. It is unpleasant. Eleven days a year, the tide reaches 44 inches, flooding the piazza to 16 inches. Last year, the water twice reached 52 inches, flooding the piazza to 2 feet. In a huge storm on November 4, 1966, the piazza flooded to four feet with waves rolling on top.

High water, especially when it contains salt, is damaging to the foundations of buildings, weakening them and eventually bringing them down. As noted above, it is also very demoralizing and is driving the inhabitants out of the city at a rate of 2,500 a year. Post-war population was 200,000; it is now 60,000 and falling. Venice cannot just be a collection of museums, hotels and restaurants. It needs a population pursuing a normal life to keep it a vibrant community. Without daily maintenance of properties by the thousands of private owners, most of the buildings would rapidly disintegrate. The government will certainly not spend millions to maintain empty dwellings. The Center for Global Warming in Geneva estimates that water levels in the world will rise 20 inches in the next century. Left unattended, this means the end of Venice within just a few decades. Clearly, something must be done.

Four possible solutions are frequently mentioned:

1. Raise the level of the islands comprising the city of Venice.

2. Zig-zag the openings into the lagoon and reduce their depth to slow the tidal and storm surges.

3. Re-expand the lagoon volume by breaking down the walls around the lagoon and the fish farms and removing the landfills.

4. Block the openings into the lagoon.

In 1984, Rome passed the "Special Law for Venice." It created the Consorzio Venezia Nuova (CVN), composed of the 50 largest engineering and construction companies in Italy, and charged it with finding a solution to the water problem. It also established the Commitatone, composed of heads of major government departments and chaired by the Prime Minister, to supervise the effort.

In 1989, the CVN submitted its recommendations: raise the perimeters of all the city's islands to 40 inches (one meter) above average water level and build gates to block the entrances to the lagoon. It concluded that removing the walls around the lagoon would do nothing because the surrounding land has been built up and the flood plain is gone. Computer models showed that removing the landfill and fish farms would not make a significant difference. The gates would take care of shallowing the entrance channels.

Today, every island in Venice, except San Marco, has its perimeter walls raised to 40 inches. This reduces the number of times that flood water can enter. We now await the gates. These are unusual in nature, but they are not new, having already been used in the Thames below London and outside Maastricht. The gates are 60 feet wide, 60 feet high, and ten feet thick. The 1,200 foot wide south and central lagoon openings require 20 gates each, and the northern opening requires 30. Each gate is hollow. It is connected by hinges to a cement base on the sea floor. When filled with water, the gate lies on the bottom. When air is pumped in to displace the water, the gate rises and bobs on the surface. A line of raised gates across an opening can sustain a nine-foot difference in water level from outside to inside.

Opposition to the gates appeared immediately upon their recommendation and has increased as the environmental movement has grown. The latter fears that any restriction of tidal action will stagnate the lagoon and wants to raise the city islands another 12 inches. The CVN says that the gates, at present rates of high water, would be elevated for only four hours ten times a year. The Greens reply that, if the CVN accepts that the water will rise 20 inches this century, the gates will be elevated much more often. The CVN retorts that such a rise in water makes the gates all the more necessary. Those on the side of the CVN say that the Greens would rather have a sunken city in distilled water than a live city in a less-than-perfect lagoon. And on it goes.

The government in Rome, unable to reach a decision in the face of such controversy, established an independent commission composed of experts from M.I.T., University of Padua, and A. D. Little & Company (based in Cambridge, MA). In 1997, the commission reported that raising the lagoon perimeters another foot would create enough pressure for the water to burrow under the walls and bubble up in the center of the islands. It would also require raising the height of many of the entrance doorways in Venice. The commission unequivocally supported the construction of the gates and stated that, even with the expected water rise in the next century, the gates would require elevation only 40 times a year for four hours at a time.

In December 1998, the Environmental Minister rejected the commission's report. The Veneto Region sued, and the highest court in Italy ruled in favor of the Veneto (and the gates) in June 1999. (NOTE from Dr Schmidt: the gates will now be built and the project is under way).

The Greens will likely appeal to the European Parliament and European Court, which will delay matters a while longer, but in the end, Venice will probably get its gates. Whether or not they will work remains to be seen. We can only hope.