Transcript Presentazione di PowerPoint

Comenius project “Lagoons”
wetland areas: Liminganlahti Bay
wetland areas: Barene nella Laguna di Venezia
Human influence on marine areas:
examples of the lagoon of Venice
and the Bay of Liminganlahti
Layout by
A.Yuntunen M.Molitierno e A.Santomaso
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Contents:
1. Lagoon ecosystem
2. Lagoon Environment
3. Lagoon drainage basin
4. Water pollution
5. Pollution prevention
6. Morphological degrade
7. Nature Conservation
8. High tide
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The Ecosystem Of
Venice Lagoon
Federica , Arttu and Taavetti
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Ecosystem:

It is a complex formed by a specific physical part (air, water and soil) which
is called "biotopo" and a living part (vegetables and animals) called
"biocenosi", united in many ways.
Its characteristics are:
1. Complexity of the relations
2. Equilibrium in the time (it means that the number of the organisms
remains always the same in the time)
3. Dependence by the natural and artificial environment
If you modify the environment or you change something in the complex
relations, the total ecosystem will be affected.
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Lagoon Ecosystem

About 78% of the lagoon surface is covered by
great expanses of water which are cut by a dense
network of channels of varying depth.

Of the 550 square kilometres of lagoon, 420
square kilometres are open to the tides of the
Upper Adriatic; which is the highest in all of the
Mediterranian.

There are 3 inlets to the lagoon: Lido, Malamocco
and Chioggia.

Fresh water for the lagoon comes from the
territory of the drainage basin.
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Lagoon Ecosystem
• The lagoon is a place where the land
and sea meet. The lagoon is changing
its farm all the time because of the
changing equilibrium between the
silting up and the erosion.
• Sediments from the river are floating
to the lagoon and are blocking the sea
currents and at the same time sea
currents are removing the sediments
away from the lagoon.
• Sea currents and river sediments both are very important parts of lagoon
ecosystem and they must be in equilibrium.
• If there are more sea currents than river sediments the lagoon changes to sea. If
there are more sediments from the river, the lagoon changes to land.
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Lagoon Ecosystem
"Opponesi elemento a elemento" (element opposes
element).
This is how Bernardo Trevisan described the nature
around the lagoon of Venice in 1715, considering it
as a transition enviroment between land and sea.
In this way the lagoon of Venice is no different from
other lagoons, but still it is the last of a series of
lagoons which once ran along the Upper Adriatic
from Ravenna to Monfalcone.
It's also the place where one of the greatest cities in history remained powerful
for centuries. In this latter respect, the lagoon of Venice is not just the fruit of
spontaneous evolution, but a natural environment which
has been defended artificially since the 14° century by the continual and
incessant interventions of man.
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Lagoon environments
Lasse, Brando and Irene
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Lagoon environments
Shoals:
• Salt marshes perform some
fundamental functions for the lagoon
equilibrium, acting as breakwaters
cushioning wave motion and inducing
considerable benefits form the
hydrodynamics in the lagoon.
• In fact, they determine the course of
the water currents during the ebb and
flow of the tide.
• Finally, salt marshes are an ideal
habitat for halophytic vegetation,
which acts as a purifying element of
the water.
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Lagoon environment

Salt marshes, together with mud flats and shallows, are
part of the most characteristic and fragile environments of
the lagoon ecosystem.
 Their surface areas vary according to the quantities of silt,
sand and other sediments that are washed away or
accumulated.
 If there is no longer an equilibrium between accumulation
and erosion, the salt marshes will disappear.
 For more than a century this equilibrium has been in
danger. In the last decades, the total area of salt marshes
has decreased from 72 km² to 47.5 km².
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Lagoon environment
Lagoon inlets
The tide flows in and out of the lagoon through
the lagoon inlets. For the most part, the
propagation of tides within the lagoon is
influenced by shape of the lagoon basin: its
shape is determined by the depth and routes
of the channels, the depth and expanse of the
lagoon, and the nature of the lagoon bed.
The lagoon inlets are the openings along the coastline where lagoon water is in continual
contact with sea water. In the past, there were more inlets, Today, there are three inlets
defined by jetties: in the north, the Lido inlet; in the centre, the Malamacco inlet; and in the
south, the Chioggia inlet. The maximum tidal water volume of all three of the inlets is 20,000
m³ of water per second; 350 million m³ of water are exchanged during spring tide and 175
million m³ of water are exchanged during neap tide. At Malamacco, the inlet in which the
greatest volume of water moves, the maximum tidal volume during spring tide cycles is 8,000
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m³ a second.
Lagoon environment
Coastlines

In recent times, beaches along the
littorals have suffered serious
erosion and dune areas have for
the most part disappeared owning
to the extensive development of
the territory. The Venetian coast,
which runs from the Sile river to
the Brenta river, is currently made
up of four stretches: Cavallino,
Lido, Pellestrina and Sottomarina.
These stretches are divided by the
three lagoon inlets. The littoral
strips are unstable stretches of
earth that separate the lagoon
from the sea.
They are subject to evolutionary processes
which modify their physical structure and
appearance; these processes can be
destructive (erosion caused by currents
and wave motion) or constructive (the
replenishing of beaches with new sand).
The overall coast is 46.6 km long and
covers an area of 58 km².
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Lagoon drainage basin
Marco C. , Anna J. , Maria K. and Stefania
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The drainage basin is all the region that
gives the water, collected in rivers or in
underground water, to the lagoon of
Venice.
The problems of the lagoon of Venice
are highly connected with the human
presence in the drainage basin.
This big area (1800 km²) is very
crowed: towns, village, agricultural
activities and factories are spread fill
almost all over the region.
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
The drainage basin is very large
and belougs to 3 provinces:
52% of it is in the province of
Venice, 40% is in the province
of Padova and 9% in the
province of Treviso. In total
there are 101 commons.
 The area is full of rivers. From
the north: Piave, Sile, Zero,
Dese, Marzenego, Muson,
Brenta. Many of them have
been diverted from the lagoon
since the 15th century, to avaid
the apport of sediments and the
disappearing of the lagoon.
 There are still 29 outlets into the
lagoon from the drainage
systems and the industrial
purification plants.
 All parts of drainage basin
produces pollution which is the
sum of all the activities within it
(es. Industry and agriculture)
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AGRICOLTURE:
Agricultural area covers 1100 km².
Production is very high in this area. The
farmers use pesticides and nutrients.
Which can watch into the rivers or
contaminate the water-bearing stratum.
FACTORIES:
URBAN AREAS:
There are 2500 factories and 160 000
people work there. The factories are
concentrated in Marghera (big area in the
lagoon) and also spread in all the region.
Ferlack of technical expedients these
factories are responsible for the pollution
that goes direct into the lagoon across
hydro-graphical net.
There live 1.400.000 people. They live
some in big villages and towns (for
example Treviso, S.Donà, Padova) and
also in the country.
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Water pollution
Laura K. - Beatrice - Giulio
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INDUSTRIAL POLLUTION

Between 1950 and 1970, without
specific legislative controls and with
a fast industrial development, the port
systems of Marghera (chemical, iron
and steel works and refineries of
petrol ) drained their waste into partly
the lagoon and partly into dumps.
 The situation was improved in
the1980s, with the constructions of
purification plants which are the 80% of
the industrial drainages of Marghera
and Mestre. The effect of industrial
pollutants dumped in the past, still
remains as you can see in the map.
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AGRICULTURE POLLUTION
Nitrogen
53% Agriculture
31% Office-habitantschool
8% Industry
8% Other
Phosphor
39% Office-habitantschool
38% For animal
8% Agriculture
8% Industry
Agriculture is
responsible for many
nutrients in the lagoon;
some others derives
from other human
activities.
URBAN POLLUTION
The water pollution in historic centre of the
lagoon caused by tourism and the people who
live in Venice and throw their garbage to the
lagoon. There was no controlling how much
waste was coming from the houses through
the waste pipes.
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POLLUTION FROM OLD DUMPS
Dangerous for swimming!
There are 17 abandoned dumps and
5.000.000 cubic metres of waste
material in the lagoon. Some of the
dumps where used until 1960s without
control. Rains and tides contributed to
the diffusion of material and pollutant
substances into the lagoon.
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Pollution Prevention
Maija, Niina, Carlo and Marco
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POLLUTION PREVENTION
In order to reduce pollution in the lagoon, some different interventions are
necessary:
1.
2.
3.
4.
5.
To intercept and purify pollutants loads coming from the drainage basin,
and from the industrial areas at the edge of the lagoon or even within it.
To insulate the refuse, to avoid the pollution coming from abandoned
dumps.
To clean us polluted areas of the lagoon bed, as the industrial channels.
To eliminate the risk of an ecological disaster caused by oil (tanker
traffic).
To avoid excessive changing of the environment, like the use of bright
lamps in the channels.
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1-REDUCTION OF POLLUTANT LOADS COMING FROM THE
DRAINAGE BASIN
A lot more parts of urban areas have
been connected to the purification
plants; in many of them phyto
purification plants have been built.
The region works to obtain the
reduction of the use of nutriments and
pesticides in agriculture. Many
agricultural areas have been diverted
from agriculture and covered with forest
or at least planted with trees at the edge
of the fields, to intercept nutriments from
the water.
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2-SECURITY INTERVENTIONS FOR DUMPS
In the area lagoon there are many dumps.
In order to avoid the water pollution from
dumps there have been same
interventions; which have isolated the
deposited materials avoiding the
contamination in the water:
• Sides and bottom waterproofing
• Biogas collection
• Topsoil and vegetation
• Protection from waves
At the end, it is possible to reconvert the
areas of the dumps for public use.
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3-CLEANING UP THE INDUSTRIAL CANAL
30% of mud of the Rii of Venice and 50 % of mud of the inner channels of Marghera are full
of dangerous substances. In order to eliminate these pollutant substances from the bottom
of the channel interventions for selected removal of 500000 cubic metres of polluted
sediments were carried out in this area. All mud drained into dumps was dehydrated first in
appropriate plants (and carried to special deposit destinations classified).
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4-DISTANCING OIL -TANKER TRAFFIC
The slips full of petrol are dangerous for
the lagoon. Because they can lose it in
the water in case of accident.
Since the morphology of the lagoon and
the slow changing of the water, the risk
of an ecological disaster is enormous.
The hypothesis traced in the plan of
1992 is to move the oil-tanker traffic
from Venice to Trieste, in order to
defend the lagoon.
To bring back the oil to Marghera
there can be used other means (for
example underground pipelines, or
train transport).
- risks connected to oil-tanker traffic
- distancing oil-tanker traffic from
the intervention areas.
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5-NAVIGATION PATH
To permit the ships to enter the lagoon during the night or in case of fog, there
have been placed 300 bright lamps on both sides of the oil-tanker channel for a
total of 15 km, so changing the environment.
It is proposed to choose another way to bring the petrol to Marghera, the ships
could go to Trieste.
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Morphological degradation
Toni , Cinzia and Alessandro O.
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
The lagoon loses every year
approximately 1.100.000 m³ of solid
materials; with this rhythm of erosion
shoals and marshlands will disappear in
50 years.

The lagoon loses its shape and stretches
into a flat configuration in which the
current of the tides can expand in a
uniform way.
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THE LAGOON LOSES 1100000 m³ OF SOLID MATERIALS
EVERY YEAR:






30.000 m³ of the sediments come from
the entrance of the rivers.
70.000 m³ of the sediments come from
the erosion of salt marshes.
2.100.000 m³ sediments derive from the
re-suspension of the lagoon bed
sediments.
700.000 m³ of the sediments are go out
through the port mouths.
400.000 m³ of the dredged sediments
are re-deposited in the lagoon for the
reconstruction of marshlands and
mudflats.
1.100.000 m³ of sediments flow into the
lagoon and canals
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THE LAGOON LOSES ITS SHAPE
Causes:
 Wave motion is caused by currents, winds
and motor vessels. Waves increase the erosion
process of salt marshes and islands.
 Silt, sand and others solid material no longer
reach the lagoon and deposit on lagoon beds.
 Loss of sands (the digging out of big artificial
channels has quickened the erosion process)
 Eelgrass disappearing: The pollution and the
consequent disappearing of the eelgrass put to
risk the vegetation of marshlands, diminishing
their enrichment of organic matter in the
underwater land).
 Some fishing techniques have a divesting
effect on lagoon beds, turning them into barren
areas.
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CONSEQUENCES
 Erosion of salt marshes
 Flattening of marshland
 Disappearance of vegetation
 At the end (50 years) transformation
of the lagoon into a flat inner sea
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Nature Conservation
Alessandro, Teija and Heidi
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Actions to avoid morphological degradation:
1.
Channel dredging and reconstruction of mud flats and salt marshes
2.
Re-naturalising of reclaimed areas
3.
Restoration of the lagoon bed
4.
Re-opening of fish farms
5.
Protection plan for salt marshes
6.
Macro algae harvesting
7.
Restoration of minor islands
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1.
Channel dredging and reconstruction of mud
flats and salt marshes
New elements of the landscape have
thus been created, compensating for
those that have disappeared.
With the dredged sediment, 400
hectares of salt marshes and mud flats
were created.
2.
Re-naturalising of reclaimed areas
A total of over 10 km have been
dredged in four channels and three
tidal creeks have been created (1,3
km).
The material dredged during channel
restoration was used in the
construction of nine salt marshes and
an artificial island.
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3.
Restoration of the lagoon bed
Palude Della Rosa is a typical transition
environment between mainland and the
sea protected from human influence.
4.
Re-opening of fish farms
Valle Figheri is a fish farm that was
chosen as an experimental field to
assess the environmental and
productive effects involved in a
systematic opening of all fish farms.
The fishery was divided into two
parts: one part remained closed, the
other part, is open and regulated by
gate.
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5.
Protection plan for salt marshes
Both replenishing techniques and
the construction of faggots are
used to restore salt marshes.
Replenishing consists of extracting
limited amounts of sand from
shallows or nearby channels.
The sand is then sprayed over the
surface of a salt marsh.
6.
Macro algae harvesting
Many times a year the
macro algae has
been collected and
used for the
agriculture and for
making paper.
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7.
Restoration of minor islands
The restoration of minor islands can
be broken down into two different
categories: on the one hand
morphological restoration, and on the
other, architectural and functional
interventions.
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High tide
Laura B. , Michele and Joni
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THE PROBLEM OF HIGH TIDE

The objective of the legislation to safeguard Venice
is to guarantee the complete defence of all built-up
areas in the lagoon from high waters of all levels,
including extreme events. Ever more frequently,
Venice, Chioggia and other historic towns and
villages in the lagoon are flooded with water and
the lowest lying zones - usually the oldest and
most valuable - are now flooded almost daily,
particularly during the winter.

The risk of an event representing a danger to the
city, such as that of 1966, is ever greater. To
protect cities and towns in the lagoon, a solution
safeguarding them not just from "exceptional"
tides, but also from the most frequent flooding had
to be identified.
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


Subsidence in the lagoon area is caused by two factors: one natural and one induced
by man. The natural process is not constant in time and space: the average rate of
natural lowering in the Venice area and its hinterland at the beginning of the century
was about 0.4 mm per year.
Overall, in this century natural subsidence has been 4 cm. The man-induced factor
above all is made up of the exploiting of underground liquid resources for industrial
uses, beginning in the 30's.
The tapping of the underground water supply caused a reduction in pressure in the
subsoil and, therefore, a contraction of the ground itself, with consequent lowering.
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THE ACTIONS TO SAVE THE LAGOON



Defence from high waters:
intervention areas (works completed
and underway)
Local protection is obtained by raising the lowest
lying parts of urban areas by means of complex
measures including the raising and structural
consolidation of quay-sides, embankments and
public paved areas; protection of ground floor
property and rear-lying private and public areas such
as courtyards and gardens from flooding and
reorganisation and adaptation of the network of
underground infrastructure and the drainage system
to avoid flow-back through drains.
However, raising has precise limits beyond which it
is impossible to proceed. Local protection is thus
integrated with the mobile barriers, capable of
temporarily isolating the lagoon from the sea and
blocking the flow of the highest tides.
To oppose deterioration of banks, canal walls and
quay-sides in the lagoon and inhabited areas, long
section of these structures (that have either
deteriorated or are too low in relation to the water
level) have been consolidated and at times
restructured.
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Mo.S.E PROJECT
The mobile flood barriers are made up of lines
of flap-gates built into the inlet canal beds.
They are "mobile" because in normal tide
conditions they are full of water and lie flat in
their housings built into the inlet canal bed.
Each oscillating buoyant floodgate consists of
a box-shaped metal 'flap' attached to its
housing by two hinges. A gate is 20 m wide
and varies in height (20-30 m) and thickness
(4-5 m) depending on the depth of the inlet.
The floodgates at rest are "folded-away" into their housings buried at the
bottom of the lagoon inlets. The housing consists of prefabricated concrete
caissons which are dug into the lagoon bed so that they do not appear
above the floor of the bed. The housing also contains the service tunnels
and machinery.
Section and simulation of a floodgate in the three phases: at rest,
intermediate, in action.
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When they are at rest, the floodgates are full of
water and lie in special housings dug into the
inlet canal bed.
When a tide exceeding +100 cm is expected,
compressed air is pumped into
the gates. This empties them of water and
make them rise, until they emerge
above sea level and block the flow of the
tide.
Undulating with wave motion, the line of
floodgates temporarily divides the
lagoon From the sea. Small boats can come
back into the lagoon through the
haven. All the machinery for the management
and monitoring of operations
is housed in buildings at the side of inlet canal.
When the tide ebbs and the lagoon and the
sea reach the same level,
the floodgates are once again filled with water
and return to their housings
on the canal bed.
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