17/02/2006

The Science of Saving Venice

Anna Somer Cocks, ICON: World Monuments Fund Quarterly Magazine

The Science of Saving Venice

Plagued by record high tides and a settling landmass, the city presents one of the world's great conservation challenges.

Oh Venice! Oh Venice! When thy marble walls
Are level with the waters, there shall be
A cry of nations o'er thy sunken halls
A loud lament along the sweeping sea!

-Lord Byron, Ode to Venice, June 28, 1819


In the old days of the Venetian Republic, the doge would board his golden barge on Ascension Day to be rowed out beyond the lagoon into the waters of the Adriatic. There, he would throw a consecrated ring into the sea, saying "Desponsamuste, mare," (We wed thee, O sea).

On the night of 3 November 1966, that marriage-more than a millennium in the making-failed as a violent storm surge rolled into the city, flooding its labyrinthine canals to a depth of nearly two meters above mean sea level. Miraculously, no one perished.Yet Venice was forever changed. As debris and pollution from oil spills flowed throughout the city, its most basic services rendered inoperable, the flood threw a harsh spotlight onto the crumbling architectural fabric of Venice, which had been slowly but surely sinking into the waters of the lagoon that had given it life, unbenownst to the outside world.

Within weeks, the international community responded, pledging to aid Venice in its recovery. Working closely with the soprintendenti, or cultural heritage officials in the Italian government, UNESCO drew up a list of more than 100 structures in urgent need of stabilization and conservation and launched an appeal for funds and technical assistance. Among the first to step forward were the British Art and Archives Rescue Fund (renamed Venice in Peril in 1971) and the U.S. Committee to Rescue Italian Art (CRIA). The World Monuments Fund (WMF)-known at that time as the International Fund for Monuments- partnered with the latter and established the Venice Committee to carry out restoration work. Its example was soon followed by the formation of a number of national committees dedicated to the preservation of the city.

In that time WMF has supported some 30 restoration projects in Venice, making it one of the largest beneficiaries of the organization's time and resources, while Venice in Peril has restored more than 40 buildings and works of art, as well as financed bursaries for students of conservation to study in Venice. Other organizations have also done their part to salvage what they can of one of the world's great cities. Yet, the task is far from complete, and perhaps today more daunting than ever. The challenge is Not merely to conserve monuments, but to arrest further decay as the city continues to sink and waters continue to rise at an alarming rate.
 
Venice is built atop a group of 117 small islands-part natural, part artificial, created by driving millions of piles deep into the clays underlying the lagoon-connected by some 378 bridges. Archaeological digs have shown that Venice has been sinking at the rate of about ten centimeters a century since its founding in the late first millennium, but in the past 100 years it sank an extra ten centimeters. Industry on the mainland, which depleted natural underground reservoirs of their freshwater reserves, has caused the subsoil to compact, resulting in a water level some 25 centimeters above a mean sea level reference point established in 1897. Although this practice was stopped in the 1970s, the damage was done. As Albert Ammerman of Colgate University has put it, "Venice has lost a century in its battle with the sea."

This reduction in the margin between ground level relative to sea level, which is eroding the fabric of the city itself, is omnipresent. A line of green algae that grows at high tide is evident on the brickwork above the protective Istrian stone bases of the buildings. As the brick absorbs seawater, salts within it crystallize and degrade building materials. Within St. Mark's Basilica, one of the world's great architectural treasures, the damp has reached as high as the vaults and is causing the individual mosaic pieces to fall off.
 
In addition to the chronically high water level, there are the acque alte, seasonal floods that invade the alleys and squares most frequently in late fall, forcing the populace and visitors to walk on duckboards. These occur as a result of a high tide, a low-pressure system, and either a strong southeast wind (scirocco) that drives in extra water from the Adriatic or a northeast wind (bora) that drives a high surge of water across the lagoon.
 
The incidence of flooding has increased ten-fold in the past century because of adverse environmental changes in the lagoon. In 1900, St. Mark's Square, the lowest lying part of the city, was flooded perhaps six times a year; today, that number is more like 60. While the lagoon used to be embraced by salt marshes, capable of absorbing substantial amounts of water, kilometer after kilometer of these have been drained and paved over with cement.

Moreover, the sandbanks and shallows that once broke up and slowed down the volumes of water are today only a third of their extent a century ago.

The lagoon is also getting deeper and saltier, behaving more and more like open water, pollution having killed off sea grasses that stopped erosion. And the deep-water channel dug in the twentieth century to let tankers into the port is causing more sediment to be sucked out of the lagoon with each waning tide.
 
Compounding the physical damage, the city is suffering a social prob-lem-abandonment, the population of the city dropping from 150,000 inhabitants in the 1950s to 64,000 today. Residents are fed up with trying to lead a normal life under abnormal conditions, fomenting a poor environment in which to conduct business. Mayor after mayor has lamented the fact that Venice is losing its socio-economic diversity and turning into a mono-economy anchored in tourism.
 
Yet when the physical condition of Venice induces people to think short-term, tourism seems an attractive option with its quick return on investment.
 
When I became chairman of Venice in Peril in 1999, I realized that if we were to truly help the city, we would need to look beyond the individual restoration projects our organizations were carrying out and begin addressing the underlying problems; in other words, to treat the disease as well as the symptoms.
 
For years, politicians, engineers, developers, and environmentalists had been arguing over how to save the city. Many believed its problems could be solved with the construction of a mobile barrier between the lagoon and the Adriatic, which would hold back elevated tides. Others contend that the environmental impact of such a contraption will be disastrous if measures are not taken to address the ecological health of the lagoon.
 
I realized that amid all of the political shouting the scientists were not being heard. I rang up an old friend, Sir John Boyd, head of Churchill College, Cambridge, and said, "There must be some way of finding out where the truth lies." He agreed, and arranged for lunch with some of the best scientific and engineering minds at the university. By coffee, we had decided that a way forward was to found a three-year fellowship to gather all the extant scientific research on Venice and the lagoon, after which we would convene an international meeting of scientists from relevant backgrounds to ascertain where the balance of proof lay, and see whether there were any serious gaps in the research.
 
By autumn 2001, we had identified two researchers to carry out the work-Caroline Fletcher, an environmental chemist, would take up the Venice in Peril Fellowship at Churchill, while Jane Da Mosto working with the Consortium for the Coordination of Research into the Lagoon (Corila), a Venetian interdisciplinary university body, would be her counterpart in Italy. Chief of the project in Cambridge was Tom Spencer, head of the Coastal Research Unit. His calm, clear, expert guidance would prove invaluable.
 
The first thing to emerge was that research conducted since 1966 was not always easy to find, divided as it was between different organizations, and much of it unpublished. Nonetheless, by September 2002, the project was ready to hold scientific and technical workshops. Each-attended by 12 to 15 people, from Venice, Cambridge, and elsewhere-looked at four areas: flooding and its implications for the buildings of the city; physical and ecological processes of the Venice lagoon; modelling of the hydrodynamics, morphology, and water quality of the lagoon; and global environmental change, uncertainty, risk, and sea level rise in the northern Adriatic.
 
Twelve months later, the largest interdisciplinary meeting of scientists to discuss the Venice problem since 1969 took place at Churchill College. For three days, Italians, Britons, Americans, Russians, Dutchmen, Lithuanians, Danes, and Spaniards discussed issues of flooding and environmental change in the city in an apolitical, tension-free setting-something that, unfortunately, is very difficult in Venice itself. They considered possible solutions and compared them to the situation in other places, such as the Netherlands, the Thames estuary, and St. Petersburg, each of which had approached the problem of flooding in novel ways.
 
The most striking thing that emerged from the discussions was that no scientist present thought Venice could survive without the installation of a mobile barrier system (see page 28). Yet, they also agreed that the barriers were only part of the solution, a way to buy Venice time and that we needed to be researching and planning for the next expedient. Informally, the Dutch suggested that one day, it might be necessary to cut Venice off from the sea permanently and convert the lagoon into a sweet water lake, as they have done with a part of the Eastern Scheldt estuary. More recently, scientists from Padua University have suggested that it might be possible to pump water into the subsoil and raise the area under and around Venice by 30 cm. Both at the conference and in the years since, nearly all have agreed that there will ever be a single, definitive solution to the flooding problem.
 
Critical to carrying out any sound diagnostic and planning work on the flooding is clear communication between the various research institutions and government agencies tackling the problem. This, at present, does not exist because of fragmentation of institutional responsibilities within Italy. Reducing the pollution in the lagoon watershed, for example, is the job of the Veneto regional administration, while pollution of the actual lagoon is policed by the Magistrato alle Acque, a branch of the Ministry of Public Works. One tide-gauge network is run by a branch of central government, the Agency for the Protection of the Environment, while forecasting storm surges is the job of the town council, which in turn, has its own tide-gauges.
 
The conference also exposed the need for an integrated long-term plan for Venice in which risk analyses and cost benefit assessments are used to help guide major decisions. For example, the Dutch, who have engaged in this type of long-term planning, have decided in the future to sacrifice some of the valuable polders (re-claimed low-lying land) to the sea as part of their defence against anticipated sea-level rise. Defending them would simply cost too much. Which brings us to a crucial question: what is the survival of Venice worth in the long term? This is not a crass, philistine question but one that the Italian government needs to consider. It cannot be left as an ordinary, ad hoc item of governmental budgeting, decided at best on a three-year basis and subject to the changing priorities of different governments.
 
This past autumn, Prime Minister Silvio Berlusconi decided that the main construction phase of the barriers should go ahead. The cost of these is variously given as ?3.5 or 4.3 billion, depending on what ancillary work is included. Many Venetians, including the current mayor, fear that if all this money goes on the barriers, there will be none left for the work of equal importance: the environmental recovery of the lagoon; the research on what is to follow the barriers; the maintenance of the canals and fabric of Venice itself.
 
Finding a solution to Venice's sinking and flooding will not be an easy task, one made all the more difficult by poor communication and misinformation. In an effort to address these issues, Venice in Peril has produced a booklet La Scienza per Venezia, or The Science of Saving Venice (see page42), based on the results of the Cambridge conference. Prepared with the help of a scientific educator from London's Natural History Museum, the publication has been sent to every member of parliament in Rome and the relevant local government politicians in Venice and the Veneto. For those interested in the complete proceedings of the meeting, they too have been issued by Cambridge University Press in a comprehensive volume, Flooding and Environmental Challenges for Venice and its Lagoon: State of Knowledge (C.A. Fletcher and T. Spencer, eds.).
 
Shortly after Hurricane Katrina struck the Gulf Coast Region, I rang up a friend and colleague, John W. Day of Louisiana State University at Baton Rouge, an expert both on the Mississippi Delta and the Venice lagoon, who described Venice's problem most succinctly. "Venice is not at risk from hurricanes," he said, "because the Adriatic is too small a sea for them to develop. Yet Venice and New Orleans have much in common; they are both entirely artificial entities in environmental terms and they will survive only as long as we want them to survive. After that, Nature will reclaim them."