Encroaching Seas Test Ingenuity of Lowlands

The warning siren howls in the dark.

As always, the flood arrives on the tide.

Water slops over the rim of the city’s canals, bubbles up through drains and, as the morning hours progress, surges into the ground-floor vestibules of palaces along the Grand Canal. It leaves stripes on sills, green and brown with a sticky scum of sewage.

The wind-driven high water -- acqua alta -- is a staple of Venetian life, like an espresso and a croissant con marmellata at a stand-up coffee bar.

Porters in knee-high waders set out elevated walkways. Shopkeepers slide cofferdams across doorways. Gondoliers duck their heads as they pass under bridges arched over swollen canals.

Brackish high tides swamp the city about 100 days a year -- twice as often as 50 years ago. After a thousand years of adaptation to the water, Venice is foundering.

“There are no longer any homes at ground floor,” says Jane da Mosta, who lives with her family near the Grand Canal. “Nobody risks being drowned in their sleep.”

*

Ge Beaufort, 60, a senior hydraulics engineer at Holland’s Rijkswaterstaat ministry, shades his watery blue eyes to admire the view.

Along the broad estuary of the eastern Schelde, southwest of Rotterdam, Dutch engineers made their stand against the North Sea.

It took $3.2 billion and 19 years of construction to impose their schematic on the greenish-gray currents of the estuary.

Braced shoulder to shoulder, 65 concrete piers of the Oosterschelde storm-surge barrier tower above the churning tide in a titanic picket fence that disappears over the curve of the horizon. Each pier measures up to 100 feet high and weighs 8,000 tons.

The 5 1/2 -mile storm surge barrier of the Oosterschelde is the backbone of national coastal defenses called the Delta Works, so vast they can be seen in their entirety only from space, so crucial to the survival of the Netherlands that the government spends nearly $2 billion a year to maintain them.

Beaufort stands on the beach of a 2 1/2 -mile-long island dredged from the sea simply to hold the project’s construction machinery.

“It is an engineering monument to the most the human imagination can do to control nature,” he says. “On a higher level, it all is only a small toy.”

*

These are the water worlds.

For a thousand years, the people of Venice have let the tide wash through their city on the Adriatic Sea. For just as many centuries, the Dutch have pushed back the sea.

One lowland built an empire on reconciliation; the other on resistance.

They have warded off the water as no place else in the world. To survive, these two coastal centers seek stability along a tide line where geology, geography and the powerful whims of water offer none.

In their long struggle, all they have gained is time. Now, time may be running out.

Alarmed by the growing intensity of storms and rising seas, each of these urban lowlands is at a turning point in its struggle for the control of nature.

As planners and engineers calculate the cost of resurrecting New Orleans from the damage of Hurricane Katrina, the sobering lessons of Venice and the Netherlands figure prominently.

The Louisiana Recovery Authority estimates that it could cost $20 billion over the next decade to rebuild and strengthen the 350 miles of levees encircling the city.

It is only a fraction of what Venice and the Netherlands have spent in centuries of struggle with the sea -- and must continue to spend for as long as their ingenuity can keep nature caged.

In the century to come, global warming is expected to raise sea level between 4 inches and 3 feet. Already, the destructive power of North Atlantic storms has doubled since the 1970s. Unchecked development in the coastal lowlands compounds the growing natural hazard.

All told, more than 40 countries depend on dikes to protect coastal settlements. Nearly 50 million people live within reach of a potential storm surge.

In London, a $1-billion storm surge barrier on the River Thames stands between high water and the 60 square miles of the central city below the tide line. Since it became operational in 1982, it has been closed 83 times to prevent flooding.

This year, engineers from the Stony Brook Storm Surge Research Group urged construction of three mobile storm surge barriers to protect New York City, where a 1992 storm surge shorted out the subway system, shut down LaGuardia Airport and left parts of Manhattan under 4 feet of water.

“At the end of the game, nature does what nature wants to do,” says MIT civil engineer Rafael Bras, who heads a panel of advisors to the Italian government on water management in Venice. “Disaster strikes at its own pace.”

*

Set at sea level in a shallow lagoon, Venice was designed by its founders to harmonize with the water, from the millions of alder pilings that anchor its grand palazzi in the muck to the maze of 177 canals that serve as streets and sewers.

A surveyor’s mistake led people to settle in flood-prone New Orleans, but 5th century Italians moved into the Venice wetlands on purpose, to escape rampaging Goths and Huns. As a safe haven, so the local adage goes, the lagoon is “too shallow for invading fleets and too deep for marching armies.”

From the shelter of its mud flats and shoals, Venetians built a seafaring republic that at its height harvested the wealth of Byzantium and controlled trade throughout the Mediterranean.

They built an intimacy with the water celebrated in a marriage ceremony every Ascension Day, when city authorities formally wed the sea with a gold ring given to the waves. For 10 centuries, engineers maintained this handmade habitat with a discipline so strict that a violation of water laws could be a death penalty offense.

It has never been an easy marriage.

In the 15th century, the city’s autocrats diverted rivers to save the lagoon, blocking the silt that threatened to turn it into dry land. Five centuries later, the city’s water authorities are fighting to keep the lagoon, deprived so long of silt, from turning into open sea.

After decades of neglect, its flood controls and sea walls are so dilapidated that even a minor storm surge could be catastrophic, city engineers say. To make matters worse, sea level is rising while the city itself is subsiding half an inch per century.

By this year, the crypt of Mark the Evangelist in the city’s Basilica of St. Mark rested 8 inches below sea level, nearly 6 feet lower than when it was built in 828. Water seeps into the atrium virtually every day in winter, and the vestibule is often ankle-deep. At least seven times a year, much of the city is swamped.

When the cold bora wind blows from the northeast or the sirocco sweeps up from Africa, they drive waves across the narrow Adriatic into the Venice lagoon like stampeding cattle. The winds push an incoming tide swollen by millions of extra gallons -- just as Katrina’s storm waters surged across Lake Pontchartrain into New Orleans.

On days when those winds are especially strong, they can pile tide upon tide, as occurred on Nov. 3, 1966, when a storm surge driven by 60-mph winds left Venice deep in a turbid stew of floating furniture and drowned rats.

In that single disastrous surge, decades of municipal neglect and thoughtless industrial development surfaced.

“The flood was like an alarm bell about a process of decay,” says Da Mosta, coauthor of “The Science of Saving Venice.”

As they have done for so many centuries, engineers set out to save this city of water one inch at a time.

Along the quay of Piazza San Marco in Venice, where 14 million tourists walk every year, two workmen heave up an 80-pound paving stone, dust it with a whisk broom and wrap it in plastic.

They number it and set it gently aside on a wooden pallet.

Each stone is unique, beveled by hand 150 years ago to fit the slope of the 18th century pavement it overlaid. Fifteen inches below that is the red brick plaza of the 15th century. Four feet below that is the walkway of the 13th century.

Following a surveyor’s chalk line, the two masons smooth a thick layer of lime and sand, then tap the old paving stone back into place on top of it with an orange rubber mallet.

One antique paver at a time, the workmen raise the canal edge by 7 inches, to protect the world-famous plaza with an imperceptible ridge along the water line. At $2,000 per square yard, it is more like art restoration than urban renewal.

The $5-million project marks the fourth time in 500 years that city engineers have raised the city’s center to keep it dry.

From the 5th to the 11th centuries, Venetians raised the level of the city by 6 feet, archeologists believe. Indeed, the sea level today may be as much as 16 feet higher than when the lagoon originally formed about 6,000 years ago.

Since 2001, water authority engineers have spent almost $3 billion to refurbish the city’s sea walls, jetties and shorelines.

To restore 18 miles of protective barrier beaches, they spread 13 million cubic yards of sand, matching the shoreline’s precise shade of golden brown with the skill of a tailor reweaving an expensive suit. They anchored new dunes with a million plugs of grass and tamarisk.

But it is no longer enough to keep Venice level with the sea.

The specter of higher seas has forced the city to adopt more drastic measures.

Anything that might block the lagoon, however, must accommodate a port that handles almost one-third the harbor traffic of New York, a busy fishing fleet and the largest cruise ship terminal in the Mediterranean -- without spoiling the city’s architecture, ruining the vistas, affecting water quality or disrupting Italy’s largest wetlands.

“Everybody was pushing us to solve the flood problem by doing nothing,” says Alberto Scotti, 59, president of Technital, an engineering firm that specializes in coastal works.

But Scotti and his colleagues had a daring idea. They conceived a $4.5-billion dam that no one would see.

Scotti’s ambitious project is a mobile surge barrier called MOSE, under development by the Consorzio Venezia Nuova, a consortium of 50 construction companies and engineering firms responsible for saving Venice from the sea. The barrier takes its name from Modulo Sperimentale Elettromeccanico, the system’s prototype.

The ingenious design calls for 78 massive mobile gates to be installed across the three inlets that connect Venice to the sea. They would be hinged on the sea floor like trap doors. Under normal circumstances, the gates would remain out of sight and out of the way, parked unobtrusively on the sea bottom, the consortium’s engineers say.

But when the tide rises high enough, the gates would be pumped full of air and lifted up to block any threatening storm surge. They are designed to bob freely on the current, barely visible above the waves.

“The barrier is a door, so you can use it only when you want,” Scotti says. “When it is not in use, you don’t see it.”

The barrier is meant to withstand the highest storm tide that might occur in 1,000 years -- a level of 6.5 feet above normal. To allow for climate-related sea level changes, Scotti added an extra 2-foot margin.

Scotti and his colleagues expect that the gates may be raised, at most, five times a year for the foreseeable future.

“If you want to defend the city, you have to close the mouth of the lagoon,” says environmental engineer Andrea Rinaldo at the University of Padua, who is on a panel of experts advising the prime minister of Italy on Venice.

Based on worst-case projections of sea level rise, the gates eventually could be closed between seven and 39 times a year.

Critics worry that the barrier will destroy the city it is meant to save.

Opponents argue that a systematic restoration of the lagoon would better solve the most serious flooding problems. Cruise ships and freighters should be banned. Others suggest the entire city should be raised a foot by pumping seawater into an aquifer underlying the lagoon.

Moreover, critics predict that the gates might turn the lagoon into a stagnant cesspool. They also worry about the polluting effect of so much concrete, steel, zinc and anti-fouling marine chemicals at the bottom of the lagoon.

“The problem of Venice is not acqua alta; it is MOSE,” says Alvise Benedetti, president of the Venice chapter of Italia Nostra, which opposes the project. “There are billions of euros involved. We are not talking about science and technology. We are talking about money. This is the big problem.”

Indeed, like New Orleans, Venice can no longer afford its own renewal. Almost bankrupt, the city plans to auction a dozen of its most historic Renaissance buildings and palaces next month, to raise cash for operating expenses.

As planners in Venice ponder the future, a broader question haunts them. For whom will the city be saved -- for the millions of tourists who visit every year or for the 60,000 residents who call it home?

Caught between high tide and the high cost of living, the population of Venice has fallen faster than any other Western European city. If its problems cannot be solved, Venice will become Italy’s New Orleans, government officials warn.

Even as the underwater barrier takes shape in the inlets of the Lido, Malamocco and Chioggia, the political furor shows no signs of dying down.

On a recent sunny afternoon, a swarm of young Venetians wearing canary yellow T-shirts and yellow baseball caps drape the plaza of Santo Stefano with red-and-black protest banners proclaiming in bold block letters: “NO MOSE.”

Police gather. Inside the 15th century palazzo on Campo Santo Stefano, which houses the headquarters of the Consorzio Venezia Nuova, security guards lock the doors.

It is business as usual.

In Venice, a city of carnival masks, the politics of flood control are not so easy to fathom.

All told, 40 municipalities and nine government agencies have some stake in the renovation effort. In addition, 50 private preservation groups, including the United Nations, also have a role. Overseeing it all is a national government that has changed hands 58 times in 55 years, making systematic long-range planning unusually difficult.

This fall, Italian Prime Minister Silvio Berlusconi approved the next phase of MOSE barrier construction. “The last doubts have vanished,” he announced. “There is no way back.”

But others are not so sure.

“There is a hell of a lot of criticism,” says Rinaldo. “They want nature to take its course.

“If you let nature operate in Venice at this point, it would be the first time in 2,000 years.”

Outside the consortium headquarters, the demonstrators drift away without confronting police, folding their banners neatly for another day.

A stout woman in a rumpled black dress hands her last leaflet to a passerby.

“Disastro! Disastro!” she cries.

*

Behind the dikes of south Holland, the highest land is the berm of a railroad bed. In the lush green pastures where cattle and burly draft horses graze, dry land is a hoof print deep.

In Amsterdam to the north, jets touch down on runways 15 feet below sea level. To the south, an ocean-going vessel passes, on average, every six minutes into the harbor of Rotterdam, Europe’s busiest port. The country’s lowest point -- twice the depth of the bowl of New Orleans at 21.8 feet below sea level -- is marked by a tablet behind a car dealership.

Tilted by its geology like a listing bathtub, the Netherlands is a storm drain.

The wastewater and runoff from hundreds of waterways in Europe swirl through the low-lying Rhine and the Maas rivers by Rotterdam into the North Sea. So intricate are its coastal inlets that a country half the area of the five-county Los Angeles region has a shoreline longer than California’s coast.

Without its 1,500 miles of dikes, 120 miles of reinforced sea dunes, 3,748 miles of drainage canals, sea walls and flood control dams, two-thirds of the country would flood almost immediately.

Schooled by centuries of floods, Dutch engineers raised sea walls around their most densely populated areas to withstand the worst that might occur in 10,000 years. For additional security, the interior was divided into 53 rings of dikes, like the water-tight compartments of a crowded cruise ship.

The lowest safety standard for these interior flood walls is more than five times that of many New Orleans levees and 10 times that for Dhaka in Bangladesh, where 8 million people live behind a dike designed to withstand the worst storm expected in 50 years.

As the Netherlands -- the most densely populated place in Europe with 16 million people -- continues to grow, more people and property are placed at risk.

“Your safety standards have to become higher and higher,” says Bart Schultz, a senior advisor at the water ministry and a UNESCO professor of water and land development.

Since the Middle Ages, when farmers first started draining their fields, the Netherlands has been sinking relative to sea level at a rate of 8 inches a century. Sea level also is rising. The 1-degree temperature increase of the past century caused the local sea level to swell by 4 to 9 inches.

Twice in the last decade, so much storm water funneled into the Rhine and the Maas rivers that high water overwhelmed the dikes.

“When it is raining now,” says Wim Bijl, a hydraulic planner at the Rijkswaterstaat, “we have to pump very hard.”

The defining modern moment for the Dutch was the flood of 1953 -- arguably the worst in 500 years.

Beaufort remembers it well. He was 8 years old.

He climbed to the top of the earthen dike near his home in Goes, helped up the steep slope by his father’s hand. As far as his young eyes could see, there was water where villages and farms had been. “I saw a dead horse floating and a wild sea.”

Before dawn on Jan. 31, the North Sea smashed through the dikes of Zeeland and South Holland in 400 places.

So swiftly did the roiled sea rampage through the delta lowlands that 1,835 people drowned -- many of them in their sleep.

For 20 consecutive hours, gale-force winds swept the coast. At 3 a.m., the spring tide also surged. Winds reached 80 mph. The high water topped at almost 15 feet above normal.

All told, half a million acres of farmland and towns were inundated -- an area four times the size of Lake Tahoe -- damaging 47,000 homes, factories and office buildings. At least 72,000 people fled to higher ground. Others were trapped on roofs and upper floors for days. About 200,000 head of livestock drowned.

The Dutch realized they would have to remake the entire country.

To start, they decided to raise all existing dikes in the region to withstand a storm surge 5 feet higher than the 1953 flood level. Then they would wall off the estuaries that had funneled the high tide so far inland.

In all, the engineers decided to girdle the coast in a corset of eight immense dams and sea barriers. All but two river outlets would have to be closed.

No one had ever attempted to alter so much coastline.

Dutch hydraulic engineers estimated that the project would cost about $812 million and take 25 years. It has taken 42 years and so far cost $5.4 billion.

“It is an enormous amount of money,” says Bijl, the Rijkswaterstaat hydraulic planner. “But it is less than the damage to New Orleans, and it is less than the damage to the Netherlands in 1953.”

Methodically, they amputated the fingers of the sea.

The swagger and sophistication of these master builders grew with every caisson of concrete lowered into place. They juggled building blocks that weighed a thousand tons and, inlet by inlet, turned saltwater into sweet. They built for the ages, with design lifetimes measured in centuries.

The finishing touch was to be a dam 6 miles long across the Oosterschelde estuary southwest of Rotterdam. It seemed safer -- and cheaper -- to close the inlet than to reinforce 75 miles of dikes along a tidal basin where the water level fluctuated as much as 9 feet every day.

As construction began to block the tide, however, people started to worry. The estuary was dying.

The fate of the estuary itself -- the health of its mud flats, salt marshes and sand banks -- started to weigh as heavily on the public conscience as national safety.

The Delta Works, conceived to withstand so much hydraulic pressure from the sea, found its designs undermined from the land side by a tide of opinion.

By 1975, the government ordered that the dam be turned into the largest storm surge barrier the world had ever seen.

“The political compromise was to design a dam that would let the water through,” Beaufort says. “That was a huge change in thinking.”

For the penultimate project of the Delta Works -- a surge barrier almost two miles long, inset with 62 sliding steel gates, that had to be assembled in a turbulent sea -- engineers in the Netherlands were challenged as never before.

They had to invent ways to prefabricate components on an unprecedented scale, then develop the means to anchor their concrete constructions firmly in a swirling sea floor. They designed ships and floating cranes to muscle the 18,000-ton piers into place.

To run it all, they built an electrical plant with the capacity to power a town of 45,000 people.

When completed, each set of piers cradled a steel gate up to 40 feet high and weighing as much as 480 tons. Together they formed a fence of sliding sluice gates to control the 264 billion gallons of sea water surging in and out of the estuary every six hours on the tide.

On the barrier’s outermost flank, the master builders painted three red stripes.

The first marked the level at which the surge barrier would normally close -- 9.8 feet above mean sea level. The second marked the local height of the 1953 flood -- 13.7 feet above mean sea level. The last marked the highest level the barrier was designed to contain -- 17 feet of high water.

When Queen Beatrix dedicated the barrier in 1987, its height seemed a safety margin sufficient for 200 years.

Based on climate change scenarios, however, water ministry planners recently started to consider the possibility that higher seas could generate storm surges almost 7 feet above the barrier’s limit.

To strengthen the entire Delta Works, the government recently allocated an additional $1 billion, but in light of Hurricane Katrina, Dutch planners hope to double or even triple that, says Pier Vellingas, dean of environment and Earth sciences at the Free University in Amsterdam.

To withstand a 2-foot rise in sea level predicted over the next century, planners calculated that an additional $19 billion may be required.

“On top of that, we are now concerned that a safety margin of one in 10,000 is still too high a risk,” Vellingas says. “In the highly urbanized area, you might want to go for a safety level of one in a million.”

Behind the barricades of the Delta Works, however, the silt of second thoughts continued to deepen.

The Rijkswaterstaat’s engineers saved the lowlands, but their bulwarks destroyed fishing grounds and shellfish farms.

Saltwater marshes became freshwater lakes. Mud flats and sand banks disappeared. Once-lively streams stagnated. Polluted sludge settled in river bottoms instead of being swept out to sea.

Under pressure, planners agreed to leave the sluice gates of the surge barriers ajar most of the time, restoring a trickle of tidal flow. In the early 1980s, the Rijkswaterstaat engineers proposed to raise the river dikes along the Nieuwe Waterweg to even greater heights, at a cost of $970 million.

A quarter of a mile wide, the waterway could not be closed by a dam because it was the main channel for the port of Rotterdam, home to a million people and the busiest shipping center in the world.

For the residents of Rotterdam, it was the last straw.

The construction would disrupt riverside neighborhoods for 25 years. Historic homes would have to be razed. And the dikes would have to be raised again in not so many years.

They decided instead to build the largest swinging storm door the world had ever seen.

Rather than a conventional dam, the designers conceived a pair of movable gates that could close the 1,200-foot-wide river channel whenever high water threatened Rotterdam.

Each swinging arm is as long as the Eiffel Tower is tall and contains twice as much steel. They pivot on 680-ton ball joints that flex like a human shoulder joint. To withstand the press of flood tide, each mammoth hinge is braced by a foundation block that weighs 52,000 tons.

The $500-million barrier, completed in 1997, is capable of withstanding “the heaviest conceivable storm once every 10,000 years,” Bijl said.

Even in the Netherlands, where the national seal depicts a lion treading water, the vigilance of flood control is difficult to sustain from one generation to the next.

“We have been doing this for a thousand years,” Beaufort says. How long must they continue?

He smiles.

“Forever.”