Venicecity of waterhas always had to live with the sea. Its history has been a story of cohabitation with water and tidesdecisive, pivotal elements of Venetian culture.
We no longer live on water nor land. From the year 589 and attributed to Paolo Diacono, this is the most ancient testimony of flooding which struck Venice.#
Painters and etchers have made their contribution as well in portraying this phenomenon of extreme high tides. In these etchings, we see Saint Marks Square under water, and already equipped with elevated walkways.
The Republic of Venice, over the centuries, completed massive projects which, even today, protect the Lagoon from the full force of tidal surges.
These protective walls, called murazzi, were made at the end of the 1700s out of Istrian stone blocks, permanently substituting the wooden pilings previously used.A stone barrier 7 miles long, built to protect the narrow island of Pellestrina and the Lagoon from the full force of the sea.
Over the centuries, flooding due to very high tides has been quite variable, but its frequency over the last few decades has progressively increased.
From an average of 10 cases per year during the first half of the 1900s, we have reached the current 60 cases per year.
voice over:
Ettore Vio, Architect & Curator of Saint Marks Basilica
We are in the lowest-lying part of the city, the entrance atrium of Saint Marks Basilica, one of its oldest parts, little more than two feet above sea level, and this year the level of the tide reached the atrium more than 200 times.
speaker:
The causes of this dramatic increase are due to the combined effects of two factors: subsidence, the downward settling of the city, and eustatism, rising sea levels. Subsidence and eustatism have caused, during the past century, a loss of more than 9 inches of the city, with respect to sea level.
To see how much the difference between the levels of city streets and canal water has diminished during the last few centuries, just look at the characteristic doors on the water, now largely submerged and often rendered useless because full of water.
The same way, the steps along the sides of canals are usually covered by water.And the layer of Istrian stones, which was supposed to insulate the walls of fine buildings from rising dampness, is now often under water. This direct contact between saltwater and plaster rapidly corrodes the walls.
voice over:
When the water comes in, it not only ruins the floors, but the marvellous, rare marble as well, and the walls. The walls soak up the saltwater, whose salts are absorbed all the way up to the level of the mosaics, where the plaster holding the mosaics is severely deteriorating.
In the 1966 flood, the water reached 6½ feet above sea level, and this is the mark that has remained in the Basilica.
In the years since then, it has reached levels like this, and like this.
speaker:
In recent times, the construction of several deep-water channels and wharves designed for docking big ships has progressively restricted the huge amounts of sand and sediments which the sea used to pour into the Lagoon. By dredging out the so-called Oil Tanker Channel, leading from the harbour mouth of Malamocco to the industrial port of Marghera, the rapid flow of rising sea water into these protected waters has been favoured. The continual disappearance of sand-bars inside the Lagoon, which in 1901 covered 90 sq. km. of its surface and today have been reduced to half that area, with only 47 sq. km. remaining, constitutes one of the most serious warning signals of the erosion process now devastating the Lagoon.
Without the presence of mud-flats (soft land normally under water) and sand-bars (more solid land normally above the waterline), entering tidal waters encounter few obstacles which can impede their flow, thus increasing the strength with which they come in, and hence erosion . The Lagoon, by losing these traits as a barrier against outside waters, is more and more exposed to the waves of its ancient friend and enemy: the sea.
In order to fight erosion, many sand-bars today are protected by pilingsthousands of wooden logs planted in the mud. They let water filter through while holding back sediments that would otherwise be washed away by tides and wave action.
Sandbarsrich in plant-life able to survive in a wet environment, but poor in fresh waterconstitute an extraordinary habitat for many species of birds as well.
Flooding in Venice has always stirred peoples imaginations. In these film sequences from 50 years ago, we can see just how this phenomenon can be described with artistry and style.
Today, more and more frequent high tide flooding is steadily worsening living conditions in the city, with evident social and economic consequences: flooding makes stores and storage rooms in Venice unusable. More than 2,200 ground-floor homes risk flooding.
voice over:
Ornella Caon, French Bookstore
The high tide comes in, and an hour or two later goes out; we clean everything up, but the walls and floor remain impregnated with water, and we are stuck in this dampness for days and days since the flooring keeps on sweating the water it has absorbed. The books soak up the salt, which reaches up to 7 feet, I think. Here its all flaking off; these were bricks, and the wall was redone only 10 years ago.
voice over:
Gianfranco Vianello, Bar Colleoni
Water reaches this square at an average of 3½ feet above sea level, and this winter it came in here 4 times; last time especially, there was a foot of water in here.
We didnt have any damage since were fairly well prepared: weve raised all the motors and the dishwasher, and removed everything that might be ruined. Other bars in Venice had damage, and I know that our association has presented a request to City Hall, but I dont know how that turned out.
Just look at Holland: the whole countrys below sea level, and not a drop gets in; I dont see why we, who are nearly 3 feet above sea level in Saint Marks Square, are not able to stop this water.
speaker:
We are in the heart of Castello, one of the most working-class areas in the city. A merchant invites us into his shop to show us where the latest flooding got a few days ago.
voice over:
Bruno Carraro, Watchmaker
This is the mark the latest flooding left when it got 2 inches above the mirror. During the Nov. 4, 1966 Flood, the water knocked over everything, including cases, watchbands, and alarm clocks that had just arrived a day earlier. It looked like the end of the world!!
speaker:
The most violent and dramatic flood to hit Venice was the one on Nov. 4, 1966, when the sea, driven by a strong wind from the south, broke through the stone breakwater in several points, forcing the high tide up 6½ feet above sea level. The city was under 3 feet of water, causing inestimable damage. The lack of warning systems made it impossible to save anything on ground floors. It was then that people began to realise that the very survival of the city would no longer be certain if no one intervened to defend it. Since 1979, the City of Venice has been operating the Tide Prediction and Communication Centre, which has the job both of letting the inhabitants know about what the tides are doing as well as sounding the alarm when exceptionally high tides are predicted.
The Tide Centre, through its telematic tidal measurement network located at key points both within the Lagoon and the Adriatic Sea, keeps the tidal situation under constant control.
Today, the incoming data forecast a high tide of 3 feet, 8 inches, at 10 a. m.
Consequently, the warning devices which advise residents of the imminent high tide are set into action:
· The Call Manager is activated, which automatically phones people living on low-lying ground floors, as well as shop-keepers: (voice over: Good morning! The next maximum high tide of 110 cm is predicted for 10 a. m. on Monday)
· When a high tide of 110 cm or more is forecast, early-warning sirens go off throughout the city and its outlying islands 3 to 4 hours beforehand.
· A tide bulletin, up-dated in real-time, can be heard on 60 phone-lines by those who call: (voice over - the next maximum high tide of 110 cm is predicted for 10 a. m. today. The tide is quite high.)
· The teams that set up 2½ miles of wooden walkways are put into motion along the primary pedestrian routes throughout the city so that the main offices and services of public interest may be reached.
· Authorised agencies furnishing vital services are notified: public and emergency means of transportation are no longer able to pass under bridges.
speaker:
Much of Venice is too low lying with respect to average sea level, and should therefore have its pavement raised and canal banks redone so that they will be able to stand up against 1 metre tides.
This local intervention includes the raising and restoration of areas along canals or which are generally subject to greater flooding.
These projects are to be co-ordinated with re-adapting the infrastructure network, canal dredging and the maintenance of foundations, buildings and boardwalks.
In this particular area, a crucial point for pedestrian traffic, resurfacing work raising the street level to 1 metre above sea level has almost been completed, protecting it from high tides up to that height.
Once public walkways have been raised, the level of ground floor homes should be taken care of.
Even for Saint Marks Square, flooded 50 times a year, work is scheduled to be done to defend it from high tides up to 100 cm. above sea level.
· In order to impede underground infiltration without changing the surface level of the Square, a waterproof cement-composite membrane will be placed about 40 cm below the surface.
· To avoid flooding rising up from the drains, a new system for gathering and getting rid of rain water will be designed.
· Finally, to keep back water coming in from the bay, the dock in front of the Square will be raised.
· Stores and ground floors around the Square will also be protected from this water by using holding basins, raising floors, and putting waterproof membranes into place.
· As with the Square, the floor and walls of the Atrium of the Basilica will also be insulated using waterproof membranes.
voice over:
We have a system of holes at the lowest points, small drains actually where the water comes in since our network of pipes is connected to outside canals, and there really is no alternative.
The work to be done on the Square cannot ignore the Atrium of the Basilica for the simple reason that if the water coming in and out of the Square is kept under control, but not ours, then we may be subject to tidal water pressure, however limited, with the risk of displacing and ruining our floor, or if we keep the drains, water will come in here and we will turn into a fountain pouring water into the Square.
speaker:
Thanks to this project, which will last 5 years and cost about 50 million dollars, most of the high tides now flooding Saint Marks Square will be taken care of.
voice over:
The 110 cm level does not create great problems for the city of Venice since services in the city have been organised so they can continue regularly up to 120 cm.
Problems start when we go from 11% of the city flooded at 110 cm to 120 or 140 cm, where the civil defence plan for the city is activated. At this stage, the city goes into a sort of paralysis since public transportation practically disappears, and the elevated wooden walkways along pre-established routes throughout the city start to float away; so the entire network of walkways must be taken down.
World scholars disagree about how the mean sea level will change. One-hundred-year projections go from the most conservative estimates, with a 6 to 8-inch rise in average sea level, to the most pessimistic ones, with a 3-foot rise or more. We are taking into account these 9 inches we have lost during the past century, and are now starting to see, perhaps, a small increase in recent years.
Personally, I would tend to forecast an 8- to 12-inch rise in average sea level during the next hundred years.
speaker:
The currently rising sea level is a serious threat and challenge for this city.
CREDITS
A Controcampo Production
Venice
Cameramen:
Danilo Vivan
Lorenzo Gagliardi
Editing:
Raffaele Usicco
Research:
Valentina Simionato
Narrator:
Bruce Wilson Boreham
A special thanks to the Guido Vianello family for the scenes from the film Venezia: le morte stagioni (= Venice: the Dead Seasons) and to the Tides Office of the City of Venice.
We no longer live on water nor land. From the year 589 and attributed to Paolo Diacono, this is the most ancient testimony of flooding which struck Venice.#
Painters and etchers have made their contribution as well in portraying this phenomenon of extreme high tides. In these etchings, we see Saint Marks Square under water, and already equipped with elevated walkways.
The Republic of Venice, over the centuries, completed massive projects which, even today, protect the Lagoon from the full force of tidal surges.
These protective walls, called murazzi, were made at the end of the 1700s out of Istrian stone blocks, permanently substituting the wooden pilings previously used.A stone barrier 7 miles long, built to protect the narrow island of Pellestrina and the Lagoon from the full force of the sea.
Over the centuries, flooding due to very high tides has been quite variable, but its frequency over the last few decades has progressively increased.
From an average of 10 cases per year during the first half of the 1900s, we have reached the current 60 cases per year.
voice over:
Ettore Vio, Architect & Curator of Saint Marks Basilica
We are in the lowest-lying part of the city, the entrance atrium of Saint Marks Basilica, one of its oldest parts, little more than two feet above sea level, and this year the level of the tide reached the atrium more than 200 times.
speaker:
The causes of this dramatic increase are due to the combined effects of two factors: subsidence, the downward settling of the city, and eustatism, rising sea levels. Subsidence and eustatism have caused, during the past century, a loss of more than 9 inches of the city, with respect to sea level.
To see how much the difference between the levels of city streets and canal water has diminished during the last few centuries, just look at the characteristic doors on the water, now largely submerged and often rendered useless because full of water.
The same way, the steps along the sides of canals are usually covered by water.And the layer of Istrian stones, which was supposed to insulate the walls of fine buildings from rising dampness, is now often under water. This direct contact between saltwater and plaster rapidly corrodes the walls.
voice over:
When the water comes in, it not only ruins the floors, but the marvellous, rare marble as well, and the walls. The walls soak up the saltwater, whose salts are absorbed all the way up to the level of the mosaics, where the plaster holding the mosaics is severely deteriorating.
In the 1966 flood, the water reached 6½ feet above sea level, and this is the mark that has remained in the Basilica.
In the years since then, it has reached levels like this, and like this.
speaker:
In recent times, the construction of several deep-water channels and wharves designed for docking big ships has progressively restricted the huge amounts of sand and sediments which the sea used to pour into the Lagoon. By dredging out the so-called Oil Tanker Channel, leading from the harbour mouth of Malamocco to the industrial port of Marghera, the rapid flow of rising sea water into these protected waters has been favoured. The continual disappearance of sand-bars inside the Lagoon, which in 1901 covered 90 sq. km. of its surface and today have been reduced to half that area, with only 47 sq. km. remaining, constitutes one of the most serious warning signals of the erosion process now devastating the Lagoon.
Without the presence of mud-flats (soft land normally under water) and sand-bars (more solid land normally above the waterline), entering tidal waters encounter few obstacles which can impede their flow, thus increasing the strength with which they come in, and hence erosion . The Lagoon, by losing these traits as a barrier against outside waters, is more and more exposed to the waves of its ancient friend and enemy: the sea.
In order to fight erosion, many sand-bars today are protected by pilingsthousands of wooden logs planted in the mud. They let water filter through while holding back sediments that would otherwise be washed away by tides and wave action.
Sandbarsrich in plant-life able to survive in a wet environment, but poor in fresh waterconstitute an extraordinary habitat for many species of birds as well.
Flooding in Venice has always stirred peoples imaginations. In these film sequences from 50 years ago, we can see just how this phenomenon can be described with artistry and style.
Today, more and more frequent high tide flooding is steadily worsening living conditions in the city, with evident social and economic consequences: flooding makes stores and storage rooms in Venice unusable. More than 2,200 ground-floor homes risk flooding.
voice over:
Ornella Caon, French Bookstore
The high tide comes in, and an hour or two later goes out; we clean everything up, but the walls and floor remain impregnated with water, and we are stuck in this dampness for days and days since the flooring keeps on sweating the water it has absorbed. The books soak up the salt, which reaches up to 7 feet, I think. Here its all flaking off; these were bricks, and the wall was redone only 10 years ago.
voice over:
Gianfranco Vianello, Bar Colleoni
Water reaches this square at an average of 3½ feet above sea level, and this winter it came in here 4 times; last time especially, there was a foot of water in here.
We didnt have any damage since were fairly well prepared: weve raised all the motors and the dishwasher, and removed everything that might be ruined. Other bars in Venice had damage, and I know that our association has presented a request to City Hall, but I dont know how that turned out.
Just look at Holland: the whole countrys below sea level, and not a drop gets in; I dont see why we, who are nearly 3 feet above sea level in Saint Marks Square, are not able to stop this water.
speaker:
We are in the heart of Castello, one of the most working-class areas in the city. A merchant invites us into his shop to show us where the latest flooding got a few days ago.
voice over:
Bruno Carraro, Watchmaker
This is the mark the latest flooding left when it got 2 inches above the mirror. During the Nov. 4, 1966 Flood, the water knocked over everything, including cases, watchbands, and alarm clocks that had just arrived a day earlier. It looked like the end of the world!!
speaker:
The most violent and dramatic flood to hit Venice was the one on Nov. 4, 1966, when the sea, driven by a strong wind from the south, broke through the stone breakwater in several points, forcing the high tide up 6½ feet above sea level. The city was under 3 feet of water, causing inestimable damage. The lack of warning systems made it impossible to save anything on ground floors. It was then that people began to realise that the very survival of the city would no longer be certain if no one intervened to defend it. Since 1979, the City of Venice has been operating the Tide Prediction and Communication Centre, which has the job both of letting the inhabitants know about what the tides are doing as well as sounding the alarm when exceptionally high tides are predicted.
The Tide Centre, through its telematic tidal measurement network located at key points both within the Lagoon and the Adriatic Sea, keeps the tidal situation under constant control.
Today, the incoming data forecast a high tide of 3 feet, 8 inches, at 10 a. m.
Consequently, the warning devices which advise residents of the imminent high tide are set into action:
· The Call Manager is activated, which automatically phones people living on low-lying ground floors, as well as shop-keepers: (voice over: Good morning! The next maximum high tide of 110 cm is predicted for 10 a. m. on Monday)
· When a high tide of 110 cm or more is forecast, early-warning sirens go off throughout the city and its outlying islands 3 to 4 hours beforehand.
· A tide bulletin, up-dated in real-time, can be heard on 60 phone-lines by those who call: (voice over - the next maximum high tide of 110 cm is predicted for 10 a. m. today. The tide is quite high.)
· The teams that set up 2½ miles of wooden walkways are put into motion along the primary pedestrian routes throughout the city so that the main offices and services of public interest may be reached.
· Authorised agencies furnishing vital services are notified: public and emergency means of transportation are no longer able to pass under bridges.
speaker:
Much of Venice is too low lying with respect to average sea level, and should therefore have its pavement raised and canal banks redone so that they will be able to stand up against 1 metre tides.
This local intervention includes the raising and restoration of areas along canals or which are generally subject to greater flooding.
These projects are to be co-ordinated with re-adapting the infrastructure network, canal dredging and the maintenance of foundations, buildings and boardwalks.
In this particular area, a crucial point for pedestrian traffic, resurfacing work raising the street level to 1 metre above sea level has almost been completed, protecting it from high tides up to that height.
Once public walkways have been raised, the level of ground floor homes should be taken care of.
Even for Saint Marks Square, flooded 50 times a year, work is scheduled to be done to defend it from high tides up to 100 cm. above sea level.
· In order to impede underground infiltration without changing the surface level of the Square, a waterproof cement-composite membrane will be placed about 40 cm below the surface.
· To avoid flooding rising up from the drains, a new system for gathering and getting rid of rain water will be designed.
· Finally, to keep back water coming in from the bay, the dock in front of the Square will be raised.
· Stores and ground floors around the Square will also be protected from this water by using holding basins, raising floors, and putting waterproof membranes into place.
· As with the Square, the floor and walls of the Atrium of the Basilica will also be insulated using waterproof membranes.
voice over:
We have a system of holes at the lowest points, small drains actually where the water comes in since our network of pipes is connected to outside canals, and there really is no alternative.
The work to be done on the Square cannot ignore the Atrium of the Basilica for the simple reason that if the water coming in and out of the Square is kept under control, but not ours, then we may be subject to tidal water pressure, however limited, with the risk of displacing and ruining our floor, or if we keep the drains, water will come in here and we will turn into a fountain pouring water into the Square.
speaker:
Thanks to this project, which will last 5 years and cost about 50 million dollars, most of the high tides now flooding Saint Marks Square will be taken care of.
voice over:
The 110 cm level does not create great problems for the city of Venice since services in the city have been organised so they can continue regularly up to 120 cm.
Problems start when we go from 11% of the city flooded at 110 cm to 120 or 140 cm, where the civil defence plan for the city is activated. At this stage, the city goes into a sort of paralysis since public transportation practically disappears, and the elevated wooden walkways along pre-established routes throughout the city start to float away; so the entire network of walkways must be taken down.
World scholars disagree about how the mean sea level will change. One-hundred-year projections go from the most conservative estimates, with a 6 to 8-inch rise in average sea level, to the most pessimistic ones, with a 3-foot rise or more. We are taking into account these 9 inches we have lost during the past century, and are now starting to see, perhaps, a small increase in recent years.
Personally, I would tend to forecast an 8- to 12-inch rise in average sea level during the next hundred years.
speaker:
The currently rising sea level is a serious threat and challenge for this city.
CREDITS
A Controcampo Production
Venice
Cameramen:
Danilo Vivan
Lorenzo Gagliardi
Editing:
Raffaele Usicco
Research:
Valentina Simionato
Narrator:
Bruce Wilson Boreham
A special thanks to the Guido Vianello family for the scenes from the film Venezia: le morte stagioni (= Venice: the Dead Seasons) and to the Tides Office of the City of Venice.