Lagoon of Venice. Satellite images of the lagoon (May 2005). In the centre, the city of Venice. Along the coast, thin strips of land separate the lagoon from the sea. Three apertures can be seen: the port entrances, through which the tides of the Adriatic flow into the lagoon.

Venice. Birds-eye view of the city. In the centre, St. Mark's Square.

The island of Torcello. In addition to the historical island-cities of the lagoon, such as Venice and Chioggia, l Chioggia, the lagoon is dotted with numerous

Mudflats and sandbars. The mudflats, known locally as velme, are normally submerged areas of the lagoon, which only appear during low tides, while the sandbars are firm stretches of sand that almost always emerge above the level of the waters and are only occasionally submerged. The sandbars are an irreplaceable habitat for the flora, fauna and bird-life of the lagoon and have various important functions: they regulate the hydrodynamics and cushion the motion of the waves.

November 4th, 1966, St. Mark's Square. The water level rose to + 194 cm and Venice, all the islands in the lagoon and the lagoon itself were submerged by over a metre of water.

The increase in the frequency of acqua alta in Venice. The data.

Acqua alta in Venice. Flooding creates problems for residents and damages architectural structures and buildings. The higher the tide, the wider the area affected and the worse the damage.

Acqua alta in Venice. Flooding creates problems for residents and damages architectural structures and buildings. The higher the tide, the wider the area affected and the worse the damage.

Acqua alta in Venice. Flooding creates problems for residents and damages architectural structures and buildings. The higher the tide, the wider the area affected and the worse the damage.

Acqua alta in Venice. Flooding creates problems for residents and damages architectural structures and buildings. The higher the tide, the wider the area affected and the worse the damage.

Lagoon of Venice. Locations of the port entrances

MOSE System. How the barrier moves. The MOSE System consists of a series of sluice gates that lie under the water during normal tide conditions, i.e. completely invisible, and are hinged to bases on the seabed in the three port entrances. However, if a high tide is foreseen, compressed air empties the gates of water letting them rise to the surface, thus creating a continuous barrier between the sea and the lagoon for as long as is required.

MOSE System. Detail of a barrier in operation. When the MOSE System is in operation, it creates a continuous barrier between the sea and the lagoon for as long as is required, but without interfering with port activities, as it provides safe harbours and locks to allow vessels to enter when the barriers are raised: locks for pleasure craft and fishing vessels heading for Lido and Chioggia, plus a large lock for ships heading for the port of Malamocco.

MOSE System. Construction at the Lido port entrance (October 2007). In the centre, the new island between the two series of sluice gates planned for this entrance. In the foreground, the reinforced pier and the shoulder of one of the barriers. Behind the new island, part of the safe harbour and the inlet leading to the lagoon for small boats when the barrier is raised.

MOSE System. Construction at the Lido port entrance (October 2007). In the centre, the safe harbour with the inlet for entry into the lagoon by small boats when the barrier is raised. The seawards part of the safe harbour has been planned to act as a temporary area for precasting the barrier foundations. On the right, the new island between the two series of sluice gates planned for this entrance.

MOSE System. Construction at the Malamocco port entrance (October 2007). In the foreground, the new completed barrier. Behind the barrier, the inlet allowing large vessels to pass through when the barrier is raised. On the left, the temporary area used for precasting the barrier foundations. In the background on the left, the new Pellestrina beach, where the shoreline has been strengthened to create a continuous sea defence together with the port entrance.

MOSE System. Construction at the Chioggia port entrance (October 2007). The two inlets for fishing vessels when the barrier is raised and the shoulders. In the background, the old town of Chioggia.

The Pellestrina coastline before and after the creation of the new beach. The entire Venetian coastline has been boosted and protected and, where possible, the dunes have been reintroduced.

The Pellestrina coastline before and after the creation of the new beach. The entire Venetian coastline has been boosted and protected and, where possible, the dunes have been reintroduced.

The Pellestrina coastline. View of the new beach that protects the coast against sea storms.

An eroding sandbar. Signs of erosion along the edge of the sandbar caused by tides and waves, wind and shipping.

Protection of a seriously eroded sandbar. Sandbars are crucial parts of the lagoon environment: they provide an irreplaceable habitat for the flora, fauna and bird-life of the lagoon, regulate the hydrodynamics and cushion the motion of the waves. Erosion processes could well lead to their disappearance, hence the need to protect them.

Protection of a seriously eroded sandbar. Sandbars are crucial parts of the lagoon environment: they provide an irreplaceable habitat for the flora, fauna and bird-life of the lagoon, regulate the hydrodynamics and cushion the motion of the waves. Erosion processes could well lead to their disappearance, hence the need to protect them.

A sandbar in the process of construction. Sandbars are reconstructed by pouring the sediment dredged from the lagoon inlets into an area with a continuous fence around it. The surface of the sandbar is then colonised by typical plants, often especially planted for that purpose.

Re-vegetation of a reconstructed sandbar. A recently finished new sandbar, showing how pioneer plants gradually take hold (especially the saltwort), until it is completely colonised by plants.

Porto Marghera. Southern industrial canal. The banks before and after work to make them environmentally safe, thus preventing the release of old pollutants in the soil through the banks of the industrial canals.

Porto Marghera. Southern industrial canal. Detail of the works.

Island of Cerosa. The banks of the island are exposed to erosion and degradation: before and after reclaiming.

Island of Cerosa. The banks of the island are exposed to erosion and degradation: before and after reclaiming.
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immagine didascalia

Lagoon of Venice. Satellite images of the lagoon (May 2005). In the centre, the city of Venice. Along the coast, thin strips of land separate the lagoon from the sea. Three apertures can be seen: the port entrances, through which the tides of the Adriatic flow into the lagoon.


immagine didascalia

Venice. Birds-eye view of the city. In the centre, St. Mark's Square.


immagine didascalia

The island of Torcello. In addition to the historical island-cities of the lagoon, such as Venice and Chioggia, l Chioggia, the lagoon is dotted with numerous


immagine didascalia

Mudflats and sandbars. The mudflats, known locally as velme, are normally submerged areas of the lagoon, which only appear during low tides, while the sandbars are firm stretches of sand that almost always emerge above the level of the waters and are only occasionally submerged. The sandbars are an irreplaceable habitat for the flora, fauna and bird-life of the lagoon and have various important functions: they regulate the hydrodynamics and cushion the motion of the waves.


immagine didascalia

November 4th, 1966, St. Mark's Square. The water level rose to + 194 cm and Venice, all the islands in the lagoon and the lagoon itself were submerged by over a metre of water.


immagine didascalia

The increase in the frequency of acqua alta in Venice. The data.


immagine didascalia

Acqua alta in Venice. Flooding creates problems for residents and damages architectural structures and buildings. The higher the tide, the wider the area affected and the worse the damage.


immagine didascalia

Acqua alta in Venice. Flooding creates problems for residents and damages architectural structures and buildings. The higher the tide, the wider the area affected and the worse the damage.


immagine didascalia

Acqua alta in Venice. Flooding creates problems for residents and damages architectural structures and buildings. The higher the tide, the wider the area affected and the worse the damage.


immagine didascalia

Acqua alta in Venice. Flooding creates problems for residents and damages architectural structures and buildings. The higher the tide, the wider the area affected and the worse the damage.


immagine didascalia

Lagoon of Venice. Locations of the port entrances


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MOSE System. How the barrier moves. The MOSE System consists of a series of sluice gates that lie under the water during normal tide conditions, i.e. completely invisible, and are hinged to bases on the seabed in the three port entrances. However, if a high tide is foreseen, compressed air empties the gates of water letting them rise to the surface, thus creating a continuous barrier between the sea and the lagoon for as long as is required.


immagine didascalia

MOSE System. Detail of a barrier in operation. When the MOSE System is in operation, it creates a continuous barrier between the sea and the lagoon for as long as is required, but without interfering with port activities, as it provides safe harbours and locks to allow vessels to enter when the barriers are raised: locks for pleasure craft and fishing vessels heading for Lido and Chioggia, plus a large lock for ships heading for the port of Malamocco.


immagine didascalia

MOSE System. Construction at the Lido port entrance (October 2007). In the centre, the new island between the two series of sluice gates planned for this entrance. In the foreground, the reinforced pier and the shoulder of one of the barriers. Behind the new island, part of the safe harbour and the inlet leading to the lagoon for small boats when the barrier is raised.


immagine didascalia

MOSE System. Construction at the Lido port entrance (October 2007). In the centre, the safe harbour with the inlet for entry into the lagoon by small boats when the barrier is raised. The seawards part of the safe harbour has been planned to act as a temporary area for precasting the barrier foundations. On the right, the new island between the two series of sluice gates planned for this entrance.


immagine didascalia

MOSE System. Construction at the Malamocco port entrance (October 2007). In the foreground, the new completed barrier. Behind the barrier, the inlet allowing large vessels to pass through when the barrier is raised. On the left, the temporary area used for precasting the barrier foundations. In the background on the left, the new Pellestrina beach, where the shoreline has been strengthened to create a continuous sea defence together with the port entrance.


immagine didascalia

MOSE System. Construction at the Chioggia port entrance (October 2007). The two inlets for fishing vessels when the barrier is raised and the shoulders. In the background, the old town of Chioggia.


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The Pellestrina coastline before and after the creation of the new beach. The entire Venetian coastline has been boosted and protected and, where possible, the dunes have been reintroduced.


immagine didascalia

The Pellestrina coastline before and after the creation of the new beach. The entire Venetian coastline has been boosted and protected and, where possible, the dunes have been reintroduced.


immagine didascalia

The Pellestrina coastline. View of the new beach that protects the coast against sea storms.


immagine didascalia

An eroding sandbar. Signs of erosion along the edge of the sandbar caused by tides and waves, wind and shipping.


immagine didascalia

Protection of a seriously eroded sandbar. Sandbars are crucial parts of the lagoon environment: they provide an irreplaceable habitat for the flora, fauna and bird-life of the lagoon, regulate the hydrodynamics and cushion the motion of the waves. Erosion processes could well lead to their disappearance, hence the need to protect them.


immagine didascalia

Protection of a seriously eroded sandbar. Sandbars are crucial parts of the lagoon environment: they provide an irreplaceable habitat for the flora, fauna and bird-life of the lagoon, regulate the hydrodynamics and cushion the motion of the waves. Erosion processes could well lead to their disappearance, hence the need to protect them.


immagine didascalia

A sandbar in the process of construction. Sandbars are reconstructed by pouring the sediment dredged from the lagoon inlets into an area with a continuous fence around it. The surface of the sandbar is then colonised by typical plants, often especially planted for that purpose.


immagine didascalia

Re-vegetation of a reconstructed sandbar. A recently finished new sandbar, showing how pioneer plants gradually take hold (especially the saltwort), until it is completely colonised by plants.


immagine didascalia

Porto Marghera. Southern industrial canal. The banks before and after work to make them environmentally safe, thus preventing the release of old pollutants in the soil through the banks of the industrial canals.


immagine didascalia

Porto Marghera. Southern industrial canal. Detail of the works.


immagine didascalia

Island of Cerosa. The banks of the island are exposed to erosion and degradation: before and after reclaiming.


immagine didascalia

Island of Cerosa. The banks of the island are exposed to erosion and degradation: before and after reclaiming.


The lagoon of Venice

Creation

The Lagoon of Venice, influenced by the tides of the upper Adriatic Sea, is Italy's largest lagoon (about 550 km2). A succession of constantly changing, different environments from the mainland to the sea characterize the complex morphology of the lagoon, i.e. its shape: shallows, mudflats, sandbars, islands and a dense network of shipping channels. Like all lagoons, that of Venice is a constantly evolving environment, which tends to be "swallowed up" by sea, if the erosive forces of tides and waves are allowed to prevail, or to turn into a strip of land, if the sediments from rivers and the sea are allowed to build up. In the specific case of Venice, man's interventions over the centuries have been a decisive factor in a process that has enabled the lagoon to survive, unlike other lagoons in the Adriatic.

Past times

For centuries, the dominant trend was for the lagoon to gradually silt-up. To counter this process, the Venetians - aware that deterioration of the lagoon would irreparably undermine the security, wealth and power of the Serenissima – ensured that measures were constantly taken to counter this trend, thus mobilising, involving and encouraging all the top scientific and technical brains for centuries. These were major engineering works: such as those needed to ensure proper draining of the Brenta, Piave and Sile estuaries, with the cutting at Porto Viro, completed in just 4 years (1605-09), which finally diverted the River Po to the south, hence creating the modern-day delta. The Venetians also took great efforts in defending the beaches against the aggressive action of the sea, culminating in the 1700s with the construction of the murazzi in Istria stone.

Recent times

Today, the problems that undermine the balance of the lagoon's ecosystem are quite different. Changes brought about by man and Nature have triggered a process that is quite the opposite to silting-up: the relative land level is now about 24 cm lower than the sea and so settlements are now exposed to high tides (the phenomenon known as “acqua alta”) with increasing frequency and intensity; at the same time other problems also compromise the ecosystem, such as erosion of the morphological structures of the lagoon and pollution, once an unknown enemy.

A question of "pre-eminent national interest"

On November 4th, 1966, the tide reached an unprecedented level: more than a metre of water invaded Venice, the islands of the lagoon and the lagoon itself and the sea eroded the coastline. The damage was incalculable. This led to a new, modern chapter in safeguarding Venice, declared a question of “pre-eminent national interest” by the Italian government (special Law n° 171, 1973) involving joint action by the State (physical defence and environmental protection), the Veneto Region (measures to reduce pollution levels in waters draining into the lagoon), the municipalities of Venice and Chioggia (urban conservation and upkeep and socio-economic development).

ACTION TAKEN BY THE ITALIAN STATE TO SAFEGUARD VENICE AND THE LAGOON

Protection against acqua alta, protection against sea storms and environmental protection of the lagoon's ecosystem: these are the objectives of the State interventions aimed at safeguarding Venice and its lagoon, the responsibility of the Ministry of Infrastructure – Venice Water Authority, implemented by the Consorzio Venezia Nuova. This is a wide-ranging series of long-term activities in the lagoon and lagoon cities, where the sea defences and environmental recovery of the lagoon's ecosystem form a reciprocal and systemic whole.

Protection against acqua alta

The phenomenon of acqua alta has become more frequent and intense since the beginning of the last century due to land subsidence. The risk of a catastrophic event similar to that of November 4th, 1966, is always present.

The MOSE System

In order to find a definitive solution to the problem of acqua alta (both exceptionally high tides that threaten the survival of Venice and the more frequent lower tides that damage the physical structures and create problems for residents) a system of mobile dams – the MOSE System – is currently under construction at the entrances to the three ports of Lido, Malamocco and Chioggia (i.e. the inlets along the coast that join the lagoon to the Adriatic).

The MOSE System. How it works. The MOSE System consists of a series of sluice gates that lie under the water during normal tide conditions, i.e. completely invisible, and are hinged to bases on the seabed in three port entrances. However, if a high tide is foreseen, compressed air empties the gates of water letting them rise to the surface, thus creating a continuous barrier between the sea and the lagoon for as long as is required. Without interfering with the environment, since the MOSE System does not affect the natural exchange of sea/lagoon water when not in use. Nor does it interfere with port activities, as it provides safe harbours and locks to allow vessels to enter when the barriers are raised: locks for pleasure craft and fishing vessels heading for Lido and Chioggia, plus a large lock for ships heading for the port of Malamocco. At the moment the barrier is programmed to work when tides rise by + 110 cm, the level at which towns are protected by embankments and raised paving. That way, the barrier would be raised an average of 3-5 times a year, about 4-5 hours each time. The MOSE System and rising sea levels. In the future, the phenomenon of alta acqua is likely to get worse on account of the expected rise in sea levels (eustatism) as a result of climate change. The MOSE System, along with reinforcement of coastal defences, is designed to deal with a rise of up to 60 cm, a figure that is higher than recent IPCC estimates (Intergovernmental Panel on Climate Change), that foresee a rise in sea levels over the next 100 years of between 18 and 59 cm. Construction of the MOSE System, which began in 2003, will be completed in 2012.

Local protection against acqua alta

In order to counteract increasingly more frequent flooding, local defences have been introduced over recent years to protect lagoon towns and the coast by means of "raising" embankments and paving in urban areas that lie lower than sea level. This involves complex work to avoid water filtration from below and regurgitation from manholes and to render ground floors safe. There are, however, precise limits to how much the embankments and paving can be raised, dictated by the urban, architectural and monumental context of each area, and the MOSE System is therefore necessary to ensure total protection against all cases of acqua alta, including extreme events.

Progress (November 2007): The MOSE System is 37% complete and should be finished in 2012. About 90 km of embankments in town areas have been raised. About 1,200 hectares are currently protected against frequent flooding.

Protection against sea storms

The shoreline is the first, natural sea defence for the lagoon. Over the centuries, the beaches along the shoreline have been eroded and in some cases have disappeared, thus exposing the coastal towns and the lagoon to the full wrath of the sea. This erosion of the coast has been countered by a wide-ranging series of measures, now nearly complete, resulting in the creation of new beaches or the extension of existing ones. Plus, wherever possible, reinstating sand dunes, thus also restoring the natural habitat for local wild-life and plants. At the same time, the existing offshore jetties delimiting the port entrances (built in the 19th and 20th Centuries) have been consolidated.

Progress (November 2007). More than 45 km of beaches have been restored or expanded and over 8 km of dunes restored. About 11 km of the offshore jetties have been consolidated.

Environmental protection

Morphological reclaiming.

Erosion, high tides and wave motion are gradually altering the laguna, meaning that it is losing its physical characteristics as a wetland and is becoming a simple, unchanging marine environment. To counter these phenomena, an intensive action program has been introduced to safeguard habitats such as sandbars, mudflats and seabeds, plus recovery of their important ecological and hydrodynamic functions, thus also helping re-qualification of the natural and landscape aspects of the ecosystem. Measures range from re-calibration of the lagoon channels to the use of dredged silt used to recreate disappeared mudflats and sandbanks, the protection of existing sandbars using cutting-edge engineering techniques and raising of the seabed to reduce the wave height. This programme also includes restoring the shores of the minor islands. Progress (November 2007): About 1,200 hectares of mudflats and sandbars have been reclaimed, 22 km seabed protected and the shores of 12 minor islands rebuilt.

Improving water and sediment quality

Action taken by the Venice Water Authority in order to improve the quality of the lagoon water and sediments are mainly aimed at isolating the pollutants in landfill sites, used in the past for various types of waste (including industrial waste) and ensuring the safety of the canals in the industrial area of Porto Marghera (seabeds and banks) involving the removal of industrial waste built up over the years. Activities also include measures to reduce the amount of pollutants carried into the lagoon along watercourses of the general basin, recreating wetlands that act as a transition between the mainland and the lagoon and that filter and absorb pollutants, thus keeping them away from the main body of water (phyto-bio purification).

Progress (November 2007). More than 35 km of industrial canal banks have been made safe and over 320,000 m3 of polluting sediment have been dredged and disposed of in special sites. 5 former landfill sites have been insulated from the surrounding area (covering a total of 182 hectares).

Maria Giovanna Piva


400 - 1000  -   - rev. 0.1.45

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Venice and its lagoons

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