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Photo Gallery: Flood Control in Venice

Foto: Luigi Costantini/ AP

Sinking Feeling Venice's Eternal Battle against Water

Slowly but surely, Venice is sinking. The city has battled the water ever since it was founded 1,600 years ago in a marshy lagoon. Now it's working on a gigantic project to prevent the floods that threaten its future -- but experts are divided over whether it will work.

It's starting again. As usual, it begins on St. Mark's Square and the cathedral courtyard, the lowest points of the city. Water bubbles up through the manhole covers, first slowly, then more steadily. Those with sensitive noses claim it stinks; others say it smells of the sea.

Some visitors find the sight a bit unsettling, but it doesn't bother Venetians. That's how things are here, they say. Whenever winter, a full moon and a southerly sirocco wind coincide, the water level rises. That's perfectly normal, and happens a dozen times a year. But it's happening increasingly often, and gradually even the stoical Venetians are starting to get concerned.

Water from the run-off drains has now washed over St. Mark's Square. At the quayside, where firmly moored gondolas bob about, this water mixes with waves from the lagoon that lap up onto the square. The yardstick at the Punta della Salute, by the mouth of the Grand Canal, shows the water level at 80 centimeters (32 inches) above normal. But it hasn't quite reached acqua alta, the high-water mark, yet.

That only begins at 110 centimeters above normal. About four times every winter, well before this happens, the sirens wail. Venetians living in endangered areas then attempt to make their front doors as watertight as possible using sheet metal. Municipal workers set up temporary raised walkways. Once the level reaches 120 centimeters above normal, a quarter of the city is under water. After five more centimeters, the boats stop running. Everything grinds to a halt. That's acqua alta.

Most tourists welcome such an event if it happens during their visit to Venice. They excitedly shuffle across the hastily erected walkways on St. Mark's Square. Carabinieri in waist-high boots stand in the water below, hurrying the masses along: "Keep going, keep going! Don't stop!"

The experience is very different for the Venetians, for whom it means flooded basements and damp walls, even above ground. Although they are used to it, the flooding is getting worse every year. In many privately owned houses, the occupants have given up on the ground floor and only live on the upper floors. The sidewalks along the water are being resurfaced. Entire buildings are being sliced open at the water line, raised hydraulically and then placed on a higher foundation. Historically important underground structures, such as Saint Mark's crypt, are treated with plastic resin to make them waterproof.

This is raising fears among inhabitants that they won't be able to save their city after all. That's because the ground on which Venice stands is sinking and the water is rising. The city is going under, slowly but surely.

'The Purest Expression of Our Capabilities'

Does this herald the end of an historically unique experiment by daring settlers? Will the lagoon eventually take back what humans wrested from it?

Massimo Cacciari, a philosopher and a former mayor of the city, once said Venice shouldn't actually have been possible. It was, he said, "a completely unlikely, entirely artificial city" and, at the same time, "a technical masterpiece, the purest expression of our capabilities, our mental potential."

The creation of this masterpiece began about 1,600 years ago in the unsafe times of the 4th, 5th and 6th centuries. Huns, Vandals, Goths and Lombards were raping and pillaging their way across Europe. Local populations either suffered or fled.

The same was true of the Veneti, the inhabitants of villages along a large lagoon in northeastern Italy, who repeatedly had to seek refuge on islands off the coast. Life on the muddy islets was undoubtedly tough. Surrounded by water, they mainly lacked one thing: water. Rain was their only source of drinking water, since the lagoon's mixture of saltwater and freshwater was undrinkable. They ate fish, occasionally supplemented with a few vegetables from their garden. In winter, they were threatened by storm tides; in summer, they were plagued by malaria-bearing mosquitoes.

Nevertheless, they were spared invasion. The marauders may have been heavily armed and often on horseback, but they had no ships. And although the lagoon wasn't particularly deep, the raiders couldn't reach the islets on foot.

Greek Immigrant Found Way to Build on Boggy Land

When the hordes moved on, the Veneti returned to dry land. That was also the intention of the refugees who, in about AD 410, had fled the advancing Visigoths onto the Rialto group of islands, a name derived from "Riva Alta" (high shore), as they were known at the time. However, a young Greek immigrant changed the course of history.

According to a medieval manuscript, the man's name was Antinopo, and he was a "wise man." He invented a revolutionary method for building houses on boggy land, a principle that is used to this day: First, Antinopo leveled the ground. On this, he placed a foundation of stone, reeds and willow rods. Around the outside of this, he then rammed thick wooden piles made of elm or oak into the ground, laying oak planks on top. Finally, a layer of thick, heavy stones was piled on, providing a firm basis for a brick house, a fine, large house almost as stable as those on built on dry land.

Whether it was because of the continued uncertainty on the mainland or the new construction method, many Veneti began settling on the Rialto. The town grew, but as an appalled medieval chronicler wrote, the people didn't have a church.

So it was providential, at least according to this chronicler, that fire broke out at Antinopo's house "by God's will," quickly setting 24 other houses alight. It was clear the entire island would soon be in flames. In such dire straits, Antinopo and his fellow inhabitants begged their creator for deliverance, promising to build a church if the fire was put out. And, lo, the writer reported, God "miraculously" transformed the wind into an immense shower that doused the flames -- coincidentally on the day of the Feast of the Annunciation.

It goes without saying that these devout Catholics built the promised church. Three years to the day after the fire, on March 25, 421, the church was consecrated "in honor of the most holy apostle, San Giacomo" on the foundations of Antinopo's house. Thus, the Greek inadvertently laid the foundations for not only his own home, but also for Venice itself.

Most historians have their doubts about the story. They say there is no evidence to support it, that it is more legend than historical fact. Nevertheless, Venice celebrates the anniversary of its foundation every year on March 25. And whether or not it did so with Greek help, Venice slowly began developing into a city-state at precisely the time when Antinopo lived.

'White Gold' Made Venice Rich

No sooner had the Visigoths disappeared than the Huns brought the next flood of refugees. Building land became scarce. As a result, the boggy neighboring islands around the Rialto were soon being colonized, too. The settlers eventually even drove wooden piles directly into the water, laid foundations and built houses or even small artificial islands on top, thus providing building land for entire groups of houses and, later, for churches and palaces.

The Venetian economy gradually grew, based on ships used for fishing and transporting goods and on salt. This "white gold" was panned in large pools, ground in cylinders and sold at a huge profit.

About a century later, in AD 537, Cassiodor, a minister of the Ostrogoth King Theoderich, praised the inhabitants of the lagoon thus: "You live in your houses like sea birds in their nests; rich and poor in equal measure."

In actual fact, a lagoon isn't a particularly suitable place to found a city. Formed by rivers and the sea as if by the whims of nature, lagoons are fragile creations, an unstable interplay of high and low tide, seawater and freshwater, influx and drainage.

It is believed the lagoon developed about 6,000 years ago. Constantly rising sea levels since the last great ice age expanded the Adriatic Sea northward. On its northern and western edges, rivers like the Brenta, Bacchiglione, Sile and Piave dragged massive amounts of rubble and sand down from the mountains and dumped them into the sea. Over the centuries, a constantly south-flowing current channeled this sediment into elongated embankments running parallel to the coast. Bit by bit, these separated a 550-square-kilometer (210-square-mile) bay from the Adriatic. Eventually, the only access to the open water was via five gaps known as "porti".

This inland sea and its approximately 60 islands and a mass of smaller and tiny islets was probably inhabited seasonally by hunters and fisherman as far back as the 2nd century BC. "Venice stands on a kind of pudding penetrated by watery channels," says architect and Venice expert Wolfdietrich Elbert. Huge amounts of trees were cut down to try to stabilize this "pudding."

Massive Deforestation and Great Floods

For instance, 12,000 tree trunks, each about 14 centimeters (6 inches) thick and up to 3 meters (10 feet) long, were used in the construction of the Rialto Bridge alone in the 13th century. The Campanille of St. Mark supposedly rests on 100,000 posts, and the Santa Maria della Salute church on more than a million. No one can say exactly how many oak, elm, alder and poplar trees were sunk in the bottom of the lagoon. It must certainly be an unimaginably large number. Not only Venice's Italian hinterland, but also the coasts of Istria and Dalmatia on the opposite side of the Adriatic were almost completely cleared at the behest of Venetian builders. The barren landscapes of the eastern Adriatic coastline still bear witness to this deforestation.

The young city on the water grew -- but life wasn't easy. From September to April, it was threatened by hot Mediterranean sirocco winds. Storms "overflowed the Lidi and the islands of Venice with such force that it felt like another biblical Great Flood," wrote scholar and lagoon researcher Jacopo Filiasi. Masses of salty water ran into the houses, spoilt food supplies, damaged goods and threatened to salinate the wells, especially if the guards weren't able to seal them in time with clay. The enormous water pressure from the Adriatic also prevented the swollen rivers flowing down from the Alps from draining, thus driving water levels in the lagoon even higher.

In an attempt to hold back the tides, for centuries, the Venetians erected sea walls made of tamarisk shrubs, breakwaters and moles. At particularly critical or important points, they built palisades known as palades made of tree trunks. Double or triple rows of wooden piles linked by planks or iron bars formed large rectangular boxes. Filled with rocks, rubble and sand and placed by the lagoon, they acted as breakwaters.

But it wasn't a permanent solution, not least because of the wood thieves. As an 18th-century chronicler complained: "Apart from the devastating effect of the sea, the palades are also jeopardized by human wickedness, for on dark, stormy nights, people destroy all this work merely for a little wood and a handful of nails."

From the 14th century on, anyone who endangered the city's flood defenses in any way risked getting a hefty fine or even a public flogging. Felling pine trees, burning off grass, driving cattle across the dykes and removing reeds or sand were all forbidden. An old inscription from the Magistrato Alle Acque, the water protection agency, warned: "Whosoever shall dare to damage this common asset should not be punished less severely than those who damage the walls of the town. This edict shall remain in force in perpetuity."

Tuscan Clay Saves City

But even without human wickedness, the palades were not a permanent solution, either. They didn't hold back the floodwaters for long, and constantly needed to be repaired. "The palisades were ruinously expensive," writes Italian historian Piero Bevilacqua. "They cost the city-state thousands of ducats a year and seemed to be merely a Sisyphean task."

Tuscany had a solution to the problem. Both there and farther south in Rome, harbor walls had long been built using a kind of waterproof cement. Venetian lagoon expert Bernardino Zendrini finally came across this puzzolano clay in the 18th century during a trip to Tuscany.

At first, the Venetians didn't trust this new material. In 1738, they built a small first test wall near Malamocco. The following year, they built a 16-pace-wide harbor mole. "This cement bonds extremely well," noted the then-head of the water agency in amazement. "And it is so resistant that no force can separate it. Far more remarkable still, mixed with water, it quickly becomes almost as hard as stone."

In 1740, the senate released the first funds for the construction of the Murazzi, gigantic barriers made of Istrian marble and rock cemented together with puzzolano clay. For the next 30 years, the Venetians worked on an enormous wall stretching more than 10 kilometers (6 miles) from Malamocco via San Pietro in Volta and Pellestrina to Chioggia.

At the time, this wall cost the astronomical sum of 20 million Venetian lire, but the investment was worth it. Although the Murazzi also needed repairing now and again, they outlasted the Venetian republic and protect the city to this day against attack from the waters.

Silt Posed New Threat

The storm floods of the Adriatic outside the lagoon's porti weren't the only threat. Far more dangerous for the city's citizens were the rivers that gushed into the basin carrying stones, earth and sand with them.

The Venetians didn't notice the danger until relatively late. At first, the damage was almost imperceptible. But even if it had been noticed in time, it wasn't clear which elements were conspiring against the city. To this day, experts argue vehemently over the role local factors play and what influence the global ebb and flow of the oceans have.

At any rate, the Venetians realized in the 15th century that their city-state was in terrible danger because of the water they both depended on and had to protect themselves against. For about 300 years, water levels in the lagoon had been falling. Soon they would find themselves stranded, and it seemed only a matter of time before their world came to an end.

Nearby Ravenna provided disturbing evidence of what could happen. Just like Venice, Ravenna was founded in the lagoon. In the 5th century, it even became an imperial city. But, bit by bit, the magnificent city silted up, gradually losing importance and eventually disappearing into obscurity. Today, Ravenna is located 9 kilometers (6 miles) from the coast.

It was therefore hardly surprising that, in the 16th century, the famous doctor and hydrologist Girolamo Fracastoro warned that the lagoon would "dry out from the sea and become marshy, either because it silts up or because the sea withdraws from the entire bay." The scientist couldn't imagine "any human power that can resist that."

Most contemporaries took a similarly dramatic view of the situation. Fears grew that the decreasing amounts of seawater would increase the prevalence of plague and malaria in the lagoon. One contemporary predicted that the constant inflow of fresh water would "render the air so foul in summer that Venice will become uninhabitable." According to an official document, the experts saw only one possible solution: "increasing the amount of water." So they tapped the canals on the mainland.

'The Source of All Evil'

The results were fatal: Water diverted into the lagoon in this way spread out across the flat basins, evaporated in summer and -- as noted in a sarcastic report by officials following the expensive yet ultimately doomed large-scale rescue operation -- managed only to "produce the worst possible air quality." Then someone had the revolutionary idea of turning off the supply of fresh water altogether, that is, to divert the rivers flowing into the lagoon in such a way that they emptied not into the bay, but directly into the sea.

Back in 1324, attempts had already been made -- and just as quickly abandoned - to divert the River Brenta, which the Venetians considered "the source of all evil." At exactly the same time, the San Nicolo di Lido entrance to the lagoon silted up. The Venetians were convinced it was a side-effect of their large-scale surgical intervention into the maritime world.

Even though it was probably unnecessary, the Venetians forced the Brenta back into its old course in 1360. Eight years later, the little river was back in the canal. The same pattern was repeated over and over. Each time such massive projects were undertaken, the outcome was unpredictable. Building projects "turned out to be the greatest threat for the lagoon," wrote mathematician Bernardino Zendrini in the 18th century, "even though they were first praised as the most effective remedy."

In the early 16th century, with the silting-up progressing apace, the powers-that-be believed there was only one solution: Not just the Brenta, but also the other "plague-bringing venomous snakes," as even official documents termed them, were to be diverted. That meant the Musone, Tergola, Marzenego and Dese rivers -- as well as the Piave. But after the authorities had tried in vain for a century to control the Piave's path with dams, its flood waves charted their own course in 1683. Now the Sile could fit into the Piave's abandoned riverbed, and after the most northerly tributary of the Po, the Po delle Fornaci, was also diverted, the deadly danger of silting up was finally averted.

Resisting the Forces of Nature

Thanks to the largest, most expensive and most protracted engineering project in human history, the Venetians managed the seemingly impossible: They had resisted the forces of nature -- albeit temporarily. Soon thereafter, modern man started destroying the foundations upon which Venice depended for its very existence.

In 1918, work began on the development of an industrial complex near Marghera on the edge of the lagoon, complete with chemical plants, refineries and metalworking factories. Marghera and neighboring Mestre grew together, and their population numbers have quadrupled since the early 1950s to about 200,000. Meanwhile, in the same period, Venice has shrunk from almost 200,000 inhabitants to fewer than 60,000.

This is because well-paid jobs beckoned on the mainland, as did modern apartments, albeit in dreary cement high-rises, but with a bathroom and for half the price charged in old Venice. And anyone who wanted to visit their relatives simply popped over "Freedom Bridge" and was in the old town center in a few minutes.

The industrial park on the waterfront was practical for companies: Waste water was simply emptied into the lagoon -- together with highly poisonous contaminants, including dioxins, furans, mercury and lead. But nobody noticed that until the 1990s. By that time, the water by the quays of the industrial complex in Marghera was brightly colored. In places it was red, in others brown and blue from rusted iron pipes. Things have allegedly improved since then, but some canals still shimmer in all the colors of the rainbow.

To facilitate industrial transportation, the shipping lanes in the lagoon were dredged to depths of up to 18 meters (60 feet), and the passages into the Adriatic were widened to as much as 900 meters. Parts of the lagoon were drained, for instance to accommodate Marco Polo Airport, while others were bisected by roads. This would have certain consequences.

Venice Is Sinking as Lagoon Floor Drops

Since then, a million cubic meters (35 million cubic feet) of sand and pebbles have washed out of the lagoon and into open water every year. The deeper and broader shipping lanes, as well as ever increasing numbers of ships and boats, create a powerful current that is absorbed less and less by plants growing on the floor of the lagoon. That's because most of this vegetation has long succumbed to the effects of water pollution.

Scientists believe that this alone will cause the base of the lagoon to drop by 15 centimeters over the next half-century. Other factors are also accelerating the decline: Massive amounts of fresh water are being pumped out of thousands of deep wells for use as both drinking water and industrial water. Natural gas is also being extracted. All this drilling is lowering the floor.

Water levels are rising; the floor of the lagoon is dropping. According to estimates, Venice is currently 23 to 30 centimeters lower in the water than it was a century ago. And it's not stopped yet.

"The ever more frequent and more powerful high tides are not only omens of demise," warns Venice expert Norbert Huse. "They are already a part of it." Over the course of the 20th century, the chances of high water-levels increased tenfold.

A 2009 survey by the Oceanographic Institute predicted that Venice will sink ever faster in the 21st century -- and therefore be at ever greater risk of flooding. The best-case scenario has the city dropping by 17 centimeters, the worst-case scenario by 53 centimeters. US researcher Vivien Gornitz, a member of the UN's Intergovernmental Panel on Climate Change, thinks even these predictions are too cautious. She fears the city will sink by much more.

'Moses' Project to Build Giant Flood Barrier

After the great flood of Nov. 4, 1966, when water levels were 194 centimeters above normal, causing enormous damage to shops, restaurants and workshops, it took three decades for the Venetians to wake up to the fact that they needed to take drastic action. But then, almost overnight, alarm bells rang, committees were appointed, and rescue plans were discussed. Some experts suggested again rerouting the rivers that had been banned from the lagoon some three centuries earlier, directing them back into the inland waters of the lagoon. That would bring back much-needed rocks, stones and sand, they said. However, that idea was thrown out as neither technically nor politically feasible.

The search for a solution therefore turned to technical projects aimed at calming the forces of the sea. In 2001, the Italian government finally ratified the largest and possibly most expensive flood-defense undertaking of all times: the Experimental Electromechanical Module. Appropriately for an engineering feat of this nature, the Italian acronym of the project is Mose, the Italian name for the biblical character who parted the Red Sea.

In principle, 78 steel boxes will be anchored closely together in concrete foundations on the floor of the openings into the lagoon. Each of these cages is to be up to 5 meters thick, 20 meters wide and up to 30 meters high. Whenever high water levels loom, air will be pumped into the steel boxes, which will then rise up and form a flood barrier. Only very little floodwater (no more than 110 centimeters above the normal level) would then be able to get through. Nevertheless, parts of the city would already be submerged by then.

Some 1,500 people are currently involved in this gargantuan project, the cost of which is estimated at between €5 billion and €7 billion ($6.3 billion to $8.8 billion). Although it should have been finished long ago, it is now hoped the system will go into service in 2014. Nevertheless, experts are deeply divided over whether the experiment will actually pay off when the time comes.

Some think it won't make any difference. Others, including US scientists Albert Ammerman and Charles McClennen, fear it will be too effective. Studies suggest that if the water in the lagoon rises by another 30 centimeters, dangerously high water levels could be registered on up to 150 days between October and late January. That means the flood defenses would be up nearly every day. The environmental consequences of this would be disastrous. Because Venice doesn't have an adequate sewage system, large volumes of fecal matter, trash and industrial effluent are washed into the lagoon every day. Normally, these gradually drift out to sea. However, Mose would prevent such natural flushing.

Is Venice really sinking? "Who knows?" says former Mayor Massimo Cacciari. "Some scientists say one thing, others another. You can't tell the sea what to do."

Translated from the German by Jan Liebelt
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