VENISE, WHICH FUTURE?

• The lagoon of Venice

The Venice Water Authority (Magistrato alle Acque di Venezia) has introduced many measures over the years to safeguard Venice, being empowered to do so by special State laws.

Past times

The history of the Magistrato goes back five hundred years and is the story of man's many attempts at water management, the goal being to protect the old town centre and its lagoon.
The Serenissima was perfectly aware that deterioration of the lagoon would undermine the greatness of Venice and for this reason, in 1501, all responsibility for the protection of fresh and salt water was concentrated in a single body.
The lagoon is a continuously changing environment: it tends to be "swallowed up" by the sea if the erosive forces of tides and waves are allowed to prevail, or to be turned into a strip of land if the sediment carried by rivers and the sea is allowed to build up. For centuries, the dominant evolutionary trend was for a gradual silting-up of the lagoon.

The “old” Water Authority carried out some essential major works thanks to which the lagoon continued to survive over the centuries. The courses of the main rivers were diverted (the "Brenta", the "Sile" and the "Piave") so that their waters flowed into the sea outside the lagoon. The cutting of the "Porto Viro" (a major work at the beginning of the 17th Century) changed the course of the River "Po", sending it further South to create the modern-day "Po" delta.

Last but not least, various steps were taken to limit the erosion of the coastline by the sea, ending in the 18th Century with the construction of the “murazzi”.

Recent times

Today the lagoon is particularly fragile and at risk: the land has sunk some 24 cm due to both natural and man-made causes and the city of Venice and its inhabitants are regularly exposed to the phenomenon of “acqua alta”, which is becoming more and more frequent and critical. At the same time, other problems compromise the delicate balance of the ecosystem, especially pollution and sediments and the gradual erosion of the morphological structure of the lagoon.

The modern chapter in safeguarding Venice began after the dramatic acqua alta on November 4th, 1966. On that day Venice, Chioggia and all the local villages were flooded by more than a metre of water.
Since then special laws have made the protection and conservation of Venice a matter of "pre-eminent national interest". The bodies most involved in this are the Italian State (physical defences 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).

A vast system of defence works

The Venice Water Authority - nowadays part of the Ministry of Infrastructure - is responsible for fulfilling the State's obligations. There is a general Action Plan split into distinct, but systemically linked lines of action: protection against acqua alta and surges caused by storms at sea, recovery of the natural morphology of the area and putting a halt to the deterioration of the state of the lagoon.

Progress in all these areas is now quite advanced. The MoSE System is currently well under construction: this is expected to provide a definitive answer to the problem of acqua alta (including exceptional flooding that may threaten the survival of the city and its inhabitants) and to counter the predicted future rise in sea levels.
It protects the three port entrances (inlets that separate the lagoon from the sea) being basically a series of sluice gates normally sitting on the seabed that are only raised in the case of potentially high tides to separate the lagoon from the sea for as long as the emergency conditions prevail.
In order to protect against more frequent flooding, embankments and city paving have been raised along the coastline.
To protect against damage caused during storms, the shore defences have been improved by widening beaches and, where possible, reintroducing dunes behind these.
To recover the morphology of the lagoon, works are underway to limit coastal erosion thanks to an Action Plan that includes the recalibration of the lagoon inlets, the re-use of dredged sediment to reconstruct disappeared mudflats and sandbars and protect existing ones and the protection of the minor islands.

To improve the quality of water and sediments, systems have been introduced to limit the dispersion of pollutants from the old landfill sites. Banks have been made water-tight and the bed of the inlets in the industrial area of "Porto Marghera" has been dredged.

Maria Giovanna Piva

1800 - 2000 - - rev. 0.1.7