VENICE LAGOON
INTERVENTIONS FOR THE RESTORATION OF
THE ENVIRONMENT
The recovery of the lagoon morphology
The morphological wealth and complexity of the lagoon ec osystem
are gradually disappearing due to the escalating action of
a series of factors linked in a vicious circle. Erosion,
high
waters and wave motion are gradually transforming
the lagoon which is thus losing the physical
characteristics of a wetland and gaining the more
simplified and uniform characteristics of a marine
environment.
To oppose
erosion by retaining part of the sediment which would otherwise be dispersed at
sea or in the lagoon itself through natural or artificial causes is the first
objective of the morphological recovery measures aimed at restoring
functionality to the environment, hydrodynamics and natural habitat associated
with the individual elements of the lagoon environment, thus contributing to
restoring the balance of the ecosystem as a whole.
Currently, of the 1,100,000 m3 of sediment previously lost at sea, 400,000 m3 is
retained in the lagoon as a result of work carried out by the Water Authority and the Consorzio Venezia Nuova. After years of study, experimentation and monitoring
of the outcome of the work, the plans and measures now have a more natural and
environmental orientation.
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 The programme of measures
ranges from the dredging of lagoon channels and use of the dredged sediment to
construct mudflats and salt marshes to the protection of existing salt marshes
using the most advanced natural engineering techniques and, to reduce wave
motion, the raising of the lagoon bed and its consolidation by planting eelgrass.
This programme also incorporates work to restore the shores of minor islands.
Contributing
to identification of the intervention areas are a series of specific studies
enabling the lagoon to be divided into homogeneous areas defined on the basis
of local hydrodynamic, morphological, environmental and functional conditions.
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Achievements
to date
To
date, about 400 ha of mudflats and salt marshes have been reconstructed out of
the 800 specified in the General Plan of Interventions (50%) and 70 km of
channel have been dredged out of the 100 km specified (70%). In addition, the
shores of 7 out of 14 minor islands (50%) have been reconstructed for a total of
5 km.
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INTERVENTIONS FOR THE RESTORATION OF
THE ENVIRONMENT
Arrest and reversal of the
environmental decay
Abatement of
pollution in the waters flowing into the lagoon basin from the hinterland is
largely the responsibility of the Veneto Region. The scope of those measures
falling within the competence of the Water Authority - Consorzio Venezia Nuova
is to improve the quality of the lagoon with intervention in the lagoon. This
means above all preventing the dispersion of contaminants from dumps used in
the past to dispose of waste of various origins (including industrial) and
reduce pollution in the channels and canals of Porto Marghera (bottom and
sides) by removing the residues of industrial processes accumulated down the
years. The full gravity of this problem has become evident only in recent years
and it is being tackled systematically and organically.
The proposed
work is covered by a Programme Agreement for the Porto Marghera chemical industry
signed in October 1999 and includes numerous and specific studies (partly
completed) designed to provide a precise and up-to-date picture of the actual conditions
and danger to the environment.
New bed
cleaning up techniques are being experimented in other lagoon areas to block
release of the pollutants which have accumulated in the sediment over the
years. In order to prevent the risk of environmental crisis due to the
proliferation of macroalgae, periodic “harvesting” campaigns are also carried
out.
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Achievements
to date
To date, 4 of the 6 major lagoon dumps specified in the General Plan of
Interventions (67%) have been impermeabilised. At Porto Marghera, 7 km of industrial
canal banks out of the 28 mentioned (25%) are being reconstructed and 90,000 m3
of polluted sludge is being dredged out of the 400,000 specified (23%). In the
annual macroalgae harvesting campaigns carried out to date, 250,000 m3 of algae
have been removed from critical zones..
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INTERVENTIONS FOR THE RESTORATION OF
THE ENVIRONMENT
Re-opening of fish farms to tidal expansion
The
re-opening of fish farms, all situated along the edge of the lagoon, could
improve hydrodynamics and quality in peripheral areas of the lagoon with poor
water exchange. This is the objective of the re-opening activities included in
the list of work falling within the competence of the Venice Water Authority
and initiated with a preliminary pilot project in a fish farm in the south lagoon.
However,
this type of intervention has an extremely modest effect on the reduction of
tidal levels in the lagoon and, as a consequence, on the frequency of flooding.
Re-opening of the fish farms would produce an average reduction in tidal levels
in Venice of just over 1 cm.
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Achievements
to date
The first of the four pilot projects specified in the General Plan of
Interventions (25%) has been implemented in the Valle Figheri.
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INTERVENTIONS FOR THE RESTORATION OF
THE ENVIRONMENT
Exclusion of the oil tanker traffic
and introduction of navigation aids
Again with the aim of reducing the extremely serious risk of pollution
or even ecological catastrophes associated with the transit of large petrochemical
tankers through the lagoon, an Operational Plan has been drawn up to eliminate
oil tanker traffic from the lagoon. In its most recent version, the project,
developed in a number of phases and through consultation with the parties and
categories concerned, involves closing the Marghera terminal of the oil
pipeline supplying the Mantua refinery and using in its place the Genoa-Cremona
pipeline, prolonged as far as Mantua, and deviating the corresponding traffic
to Genoa; reorganisation of production and transport of petrochemical products in the Adriatic in
order to reduce the incidence on Marghera as far as possible and measures to
prevent ships not conforming fully to international safety standards from
entering the lagoon.
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Achievements
to date
To make the transit of large ships heading for Porto Marghera through
the lagoon safer, the Water Authority - Consorzio Venezia Nuova has installed a
system of lights and a series of auxiliary electronic aids along the so-called
Oil tanker-Canal linking the Malamocco inlet with the industrial zone. The new
illuminated route (sentiero luminoso) is 15 km long and guarantees the safety
of shipping even at night or in fog causing poor visibility.
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