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Geo Engineering: Venice
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  • From The Civil Engineer:  Big Project Watch
  • Project Name: Venice Tide Barrier Project (The Modulo Sperimentale Elettromeccanico project)
  • Location: Italy
  • Project Start Date: 2001
  • Expected Finish Date:
  • Expected Cost: 2.6 Billion USD
  • Description:

    The project designed to protect
    Venice from flooding and erosion involves using a string of 79 inflatable gates to stem the flow of water through Venice's three inlets into its lagoon.

Links:

New Scientist: Inflatable Dam to Protect Venice Is Approved

Venice Water Authority: Project news

Venice Water Authority: Homepage

PBS: Sinking City of Venice

The International Centre Cities on Water

Architecture Week: Saving Venice

UNESCO: Venice: duels over troubled waters

BBC: Italy rejects Venetian barrier scheme

BBC: Venice flood barriers shelved

BBC: Venice flood barriers rejected

BBC: Venice behind barriers

BBC: Venice overwhelmed by floods

BBC:Venice lagoon reveals grim secrets

BBC: Bailing out flooded Venice

BBC: Floodgates 'won't save Venice'

BBC: Scientists start Venice flood research

Find Article: Against the Tide.(Venice, Italy)

Christian Science Monitor: Costly Rescue for Merchants of Venice

Christian Science Monitor: Rising waters, sinking city

Christian Science Monitor: Plan to save Venice from the sea draws praise, doubts

Encyclopedia Britannica: Venice, Italy

The Age: Critics set to sink Venice flood barrier plans

TechTV: Saving Venice

Discovery: Saving the City of Canals

Smithsonian: Turning the Tide

MIT Tech Talk: Venice could provide gateway to 21st-century flood control method

USA Today: Can Venice be saved?

New York Times: If Sea Gates Don't Work, Call Canute

Washington Post: Venice Hopes Gates Will Turn the Tide

Amazon Book: Venice Against the Sea: A City Besieged

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Venice could provide gateway to 21st-century flood control method

Denise Brehm, News Office
November 6, 2002

Venice, historic city of canals and gondoliers, is planning to defend itself in the 21st century by building massive, swinging gates. The idea may conjure images of medieval drawbridges, but these high-tech gates won't protect citizens from foreign invaders. Instead, they've been designed to keep the marauding sea at bay.

After a centuries-long war with flooded streets, the Italian government is expected to decide later this year whether to proceed with a public-works project that would build a series of floodgates at three inlets along the lagoon surrounding the city. These gates, which will rest on the sea floor and swing upwards in response to rising tides, will cost between $3 billion and $4 billion and take eight to 10 years to construct.

Three MIT professors have been involved with the project since 1995, when they were hired to oversee a two-year environmental assessment. Since then, as the consultants who "look over the shoulders of the consultants," they have shepherded the project through twists and turns as numerous as the city's canal-streets, said Rafael L. Bras , the Bacardi and Stockholm Water Foundations Professor at MIT, who chairs the advisory committee that reports to the Venice Water Authority. His committee oversees the consultants who are designing and planning the project, called MOSE - the Modulo Sperimentale Elettromeccanico, or Experimental Electromechanical Module - after a prototype of a single gate that was built a decade ago to test some of the engineering design.

"Our job is to keep them honest, to watch for the appropriateness of the action," said Bras, a hydrologist and hydroclimatologist who was head of the Department of Civil and Environmental Engineering from 1991-2001. With him on the committee are Professor Emeritus Donald R.F. Harleman of civil and environmental engineering, and Professor Paola Rizzoli of earth, atmospheric and planetary sciences, who is also the MIT director of the MIT-Woods Hole Joint Program in Oceanography. Professor Chryssostomos Chryssostomidis of ocean engineering participated in earlier activities. Professor Andrea Rinaldo from the University of Padua is also a member of the group. Both Rizzoli and Rinaldo are Venetians.

In his own research program, Bras studies the relationship among atmospheric phenomena, surface hydrologic processes and the landforms of river basins to enhance our understanding of human impact on the global environment and to improve predictions of hydrologic events like floods.

And flooding is a phenomenon Venetians know well.

Venice is actually a collection of many small islands connected by bridges in a lagoon that's separated from the Adriatic Sea by a strip of long, narrow barrier islands. When the tides are higher than normal, water surges through the lagoon inlets and floods the city, forcing people to walk around on raised catwalks set up for these occasions. On Nov. 4, 1966, the city was under a 1.94-meter tide (nearly six and a half feet), almost 1.5 meters over the normal tide, causing the worst flooding in recent history. In 1997, Venice flooded about 100 times.

Because flooding occurs more frequently now, the ground floors of buildings have been abandoned and many people have moved away. During medieval times, Venice was a thriving metropolis of 250,000 people; today the population is a mere 60,000.

"It's hard enough to live in Venice because of difficulties in mobility; there are no cars or trucks to move goods or drive you to the market. If, on top of that, businesses have to deal with an infrastructure under constant attack, it's understandable why it's difficult to maintain a viable, vibrant city," said Bras.

Floods usually occur between October and February, when winter storms bring lower atmospheric pressure and higher winds, leading to increased tide levels. But this year, it also flooded several times in June, when the city was unprepared. "It was a disaster, like snow removal in Boston in the summer," said Bras, who added that flooding tides of 1.4 meters (four and a half feet) were once rare, but now occur almost every year.

The increased flooding is caused by two things: the city is sinking and sea level is rising.

After World War II, water needed by new industry was obtained by pumping groundwater from nearby areas. As the water table decreased, the islands began sinking. The practice of pumping groundwater was stopped shortly after the devastating flood of 1966, and the city is now sinking at the much lower rate of 0.4mm per year.

At the same time, the Adriatic Sea and other ocean waters have been rising at the rate of 1.6mm per year, perhaps due to natural causes. "It could be the ubiquitous sea level rise that occurs around the world and has been going on fairly consistently since the last glacial period," said Bras. "You can debate whether it is accelerating or not, but so far I see no evidence of acceleration."

The end result of this rising and sinking is that Venice floods when high astronomical tides - the tides induced by the moon - combine with high meteorological tides - the surge caused by stormy weather (low atmospheric pressure combined with winds).

But if the government approves and constructs the MOSE project, this combination of high tides will no longer flood the city. Instead, the rising tides will be blocked by new floodgates, which will be placed at the inlets where the Adriatic Sea enters the lagoon. The gates are designed to prevent the Adriatic Sea from flooding the lagoon at high tides in even the worst storms.

The project is a series of 79 gates - each about 30 meters high, 20 meters wide and four to five meters thick - to be installed on the bottom of the sea at inlets at Lido, Malamocco and Chioggia. Forty of the panels will stretch across Lido, the widest of the inlets. When a tide of 1.4 meters or higher is predicted, the hollow gates will fill with air and rise, creating a barrier to the seawater.

Critics fear the gates will prevent water exchange between the lagoon and the Adriatic Sea, which could damage the lagoon's ecosystem. But research on water exchange in the lagoon shows that the lagoon is flushed daily by the tides, indicating that if the gates are up during a storm, the tides will quickly flush the lagoon as soon as the gates come down.

"Pollution prevention in the lagoon is always the best practice," said Bras. "In fact, the water quality of the lagoon has been improving over the last decade in response to pollution prevention practices, so that dependence on natural flushing would be less essential. In addition, during normal periods, the gates can be opened and closed in such a way as to induce additional mitigating flushing."

Other critics claim that the design is based on outdated predictions of rising sea levels. They say the gates will become obsolete in half a century. Bras, Harleman, Rizzoli and Rinaldo addressed that criticism in an article in Eos, a publication of the American Geophysical Union, last spring.

"The bottom line is that the gates work. The barriers, as designed, separate the lagoon from the sea in an effective, efficient and flexible way, considering present and foreseeable scenarios," the authors wrote.

"I advocate that this is the only solution to the problem," Bras said in an interview. "I have no doubt that it will work for 50, 70 years. I have no way of knowing what will happen in 100 or 120 years. If we see massive rises in sea levels, then we'll have big problems in Cape Cod and elsewhere. It won't be just Venice, which will in fact be in a better position by acting now."

A version of this article appeared in MIT Tech Talk on November 6, 2002.

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VENICE TURNS TO FUTURE TO RESCUE ITS PAST

New York Times
International Herald Tribune
By Elisabeth Rosenthal
February 22, 2005

VENICE - When Jane da Mosto scrambles from the water taxi onto the front steps of her family's ancient palazzo on the Grand Canal, her gaze is tinged with mourning. The once glorious Casa da Mosto is now little more than a decaying, waterlogged shell of a building, the rising and increasingly salty water of Venice lapping at the door and eating away at  its walls.

"One day it will just fall into the canal," said Ms. da Mosto, a researcher with Corila, a consortium of groups studying the Venice lagoon in hopes of saving it.

Now, a daring multibillion-dollar construction project sponsored by the Italian government is just getting under way, in an effort to meet that goal. But many, including Ms. da Mosto, are skeptical that it will be enough."I don't like to think about where Venice might be in 100 years," she said. "It's so overwhelming and sad. Maybe it will be closed off as a lake. Maybe it will be underwater and tourists can see it from a glass-bottom boat."

The Venice lagoon is one of the world's most delicate and unstable ecosystems, a unique place where saving a dying natural habitat is crucial to preserving human culture and history: centuries of art and architecture sit within the nature preserve and will be lost if the lagoon succumbs.

And that has prompted increasingly passionate debates here about radical plans now under way to save it - plans that push at the limits of scientific knowledge and engineering capacity.

At the heart of the debate is tension between those who believe in the power of human technology to thwart the forces of nature and those who worry that Italy's master engineers, in their hubris, may only complicate Venice's problem.

The centerpiece of the Italian government's ambitious plan - called the Moses Project, after the parting of the Red Sea - is a series of 78 gargantuan movable underwater dams that would rest on the floor of the Adriatic Sea, massive barriers that would be mechanically raised above the surface when needed to block extraordinary high tide surges. Such tides, which generally now occur a few times a year, produce devastation in Venice that is rapid and, at times, disastrous, like the flood of 1966.

A prime project of Prime Minister Silvio Berlusconi, the high-tech barriers have a political weight that matches their physical heaviness, 300 tons each, and their $4.5 billion price.

"These barriers are a huge environmental intervention on a scale never done before," said Alberto Scotti, the project's chief engineer, who is as confident and pragmatic about the plan as others are emotional.

Critics worry that the huge barriers could further upset nature's delicate balance. They note that the barriers do nothing to allay the city's day-to-day deterioration, a result of more subtle forces in the dying lagoon, requiring less glamorous solutions.

Slowly sinking land and slowly rising water have left many building walls perpetually underwater. Increasing salt content in the canals threatens the
city's foundations. The death of plant life on the lagoon bed has turned once variegated channels into conduits for rushing water that pours into the city every time there is a sea squall.

"At the moment, everyone is focused on the barrier - which is very scary because it is a very inflexible and untested solution," said Ms. da Mosto, co-author of "The Science of Saving Venice," a book sponsored by Venice in Peril, a British nongovernmental organization.

"A lot of scientists think it will do the job, and a lot think it won't," she added. "I can't tell you what the solution is, but you also need to stabilize the environment. And what I do know is that the lagoon is immensely complicated, and the more one relies on diverse and reversible solutions the better."

With comprehensive computer models and feasibility studies, Mr. Scotti stands behind his design. "We have checked everything with modeling," he said with a hint of exasperation. "We have models for the morphology of the lagoon. We can reproduce the wind, weather and tides. And our models suggest this will work and will have no negative environmental impact."

Patching up Venice's continuing wounds is already an obsession, and a full-time job, for city officials and residents.

On a recent day in the Squero di San Trovaso, home of Venice's famed gondola workshops, the canals had been drained dry for repairs. Dozens of workers from Insula, a public-private partnership that maintains the canals, are poring over each centimeter of wall, patching up areas of decay  and pumping foam through bright green hoses into the walls in order to reinforce them.

"Venice has to be maintained like a boat: you take it out of water and  repair it," said Giorgio Barbarini, the driver of a water taxi. "Venice is falling apart because it is hard to maintain a whole city like that."

>From an evolutionary standpoint, Venice's decline is perhaps inevitable.

Lagoons, with their marshes and brackish waters, are transitional coastal ecosystems, tending to become freshwater lakes or to blend in with the adjacent sea over time. That process accelerates when man cohabits with this unstable bit of nature, as he has here for well over 1,000 years.

Venetians have long manipulated water to protect their city, diverting rivers in the 14th century.

But the rapid changes in the ecosystem have occurred with modernization in the 20th century. Starting in the 1930's, an industrial zone and other lands were created by pumping groundwater out of the marsh, seriously accelerating sinkage. Shipping and pollution that followed eroded many of the crucial defensive features of the lagoon that for centuries helped to keep the sea at bay.

For example, the once textured lagoon floor is now mostly flat and bereft of plants, allowing water surges from sea storms to find their way unimpeded into the city.

The result is that the average water level in Venice is 9 inches, higher than it was a century ago, and perhaps 40 inches higher than 250 years ago, according to researchers at Corila. The once brackish water is now as salty as the sea.

Global warming has not yet contributed substantially to rising water levels here, Ms. da Mosto said. Predictions of the phenomenon's eventual effect on the Adriatic vary widely: some scientists estimate a rise due to global warming of just three inches and others suggest the change may be nearly a yard.

Already, water routinely fills piazzas and seeps into churches. It backs up into homes through the sewers. It corrodes building walls never meant to be submerged. While the foundations of Venetian palazzos were built of materials that withstand water, the walls are brick and porous.

"Lots of money has gone in to replastering and replacing walls brick by brick. We call it the sacrificial layer," Ms. da Mosto said. "But in a few
years it is crumbling."

Against this backdrop, designers of the Moses Project often seem perplexed at the resistance in the city they have vowed to save. There were years of negotiations with local officials and environmental groups before construction got under way in May 2003.

Mr. Scotti noted that the project involved not just the barriers, which will be completed by 2010, but also plans to reinforce building walls to protect them from lesser floods, and designs to re-establish wetlands as
well. Critics contend that these features are poorly developed afterthoughts.

"People here just accept floods and boots as part of life," Mr. Scotti said. "But living in this condition puts them at a big disadvantage compared to people in Milan and Rome. This will mean a change of life for
them."

Mr. Scotti's engineering challenge was enormous, both in terms of the tidal force and the government's requirement that the barriers (far out at sea)
be invisible when not in use, a decision that many say unnecessarily added millions to the project.

Teams are now building artificial breakwaters to attenuate tides. Over time, thousands of steel poles will be pounded into the floor of the lagoon. To house the barriers, cement blocks, measuring about 66 yards by 44 yards by 12 yards will be embedded in the sea floor.

It is the very size of the project that terrifies skeptics, who fear that such a huge endeavor will further disturb the lagoon. While the Venice lagoon has been studied extensively by scientists, much of the work was done locally and never coordinated or presented in scientific journals, Ms. da Mosto said. As a result, the complicated ecosystem remains poorly understood, she said.

But designers say they will build slowly and with extraordinary care to create a new safe haven for Venetians - even if it is does not conform with
the lagoon's natural form. "Look, there is no natural environment to recover here in
Venice anymore," Mr. Scotti said. "It has been changed by man for hundreds of years."

"What is important is to create a lagoon with a lot of possibilities of life," he continued. "The shape will not be natural. The plants will not be the same. There will be artificial material. There are no books on how to
build a lagoon.

"We are human, so of course we are not able to reproduce what God made before."

 

 
 
 
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