Background

The unique setting of the city of Venice contributes both to its appeal and to its vulnerability to flooding and environmental degradation. The Venetian lagoon exchanges water with the northern Adriatic Sea through three large inlets. In the winter, strong winds from the south lead to abnormally high water levels in the lagoon and, at times, extensive flooding in the city. Such events are likely to increase in frequency and magnitude in the near future; accelerated sea level rise is expected to lead to progressively higher background water levels on which such flooding events will take place.

Within the next 100 years, it is predicted that sea level will rise by 4 - 6 mm per year, adding to the natural subsidence of the Venice lagoon of 1 - 1.5 mm per year. Flooding statistics from the city strongly suggest a worsening problem. In the first decade of the 20th century St. Mark's Square flooded less than ten times per year. By the 1980s, flooding was occurring 40 times per year and since September 2000 over 60 flood events per year have been recorded. The 144 cm flood of 6 November 2000, 64 cm above the surface of St. Mark's, was one of the ten most severe events since 1900, with 93% of the city under water, followed by the 147 cm event of 16 November 2002, the fifth highest on record.

In addition, the city is surrounded by an ecosystem suffering from severe environmental degradation. Agricultural, industrial and urban wastes have caused major water quality problems in the Venice lagoon. Long jetties constructed in the inlets at the end of the 19th century have greatly reduced the import of marine sediments into the lagoon and the Brenta and Piave rivers, which used to supply fine sediments to the lagoon have been long diverted to discharge in to the sea. As a result, there is a strong net loss of sediments from the lagoon. Starved of new sediments and eroded by wave attack from northerly winds, or removed by reclamation, the lagoon wetlands had been reduced to a third of their former extent at the beginning of the twentieth century.

Whilst there is no lack of scientific research that focuses on the environment of Venice and its lagoon, this information has not been organised and brought together in an accessible form which could then be consulted by those interested in the 'Venice problem'. Such an exercise will provide the foundation for a wide-ranging debate within the international scientific community about management solutions to these environmental problems, including an evaluation of those solutions being proposed.

Cambridge Environmental Initiative (CEI) and Churchill College, Cambridge in collaboration with the Venice in Peril Fund (the British Committee for the preservation of Venice) are undertaking a three-year research project focussing on the flooding and environmental challenges for Venice and the Venice Lagoon. The project is carried out in association with a number of Italian partners, in particular the Venice based Consortium for co-ordination of research concerning the Venice Lagoon System (Corila).

Our mission is to provide an international dimension to the objective study and review of information concerning key aspects of the flooding and environmental issues relevant to Venice. The scope of the project aims to:

• Support through discussions, workshops and this International Meeting in September 2003, the exchange of reliable scientific information between researchers around the world working on similar problems to facilitate a fruitful exchange of knowledge;
• Provide a well-founded and realistic analysis of the environmental issues for Venice;
• Promote widespread recognition of the flooding issues and related environmental problems of Venice.

The safeguarding of Venice has been an on-going issue since its beginnings and interventions to protect Venice in its unique setting, the Lagoon, have been undertaken for many centuries. Last century the world was awakened to the threat to the existence of Venice in the long-term by a large flood in 1966. Since then a large body of work has been on-going in Venice raising solutions to the problem of flooding and wider measures to combat issues such as environmental degradation of the lagoon system. Interventions and lagoon management have been set out in successive iterations of the special laws for safeguarding Venice (Special Law no. 171/73; 798/84; 139/92). The Italian Government decided on 6 December 2001 to continue with planning for a number of interventions to regulate the hydrodynamics of lagoon/sea exchanges and environmental restoration of the lagoon ecology and morphology. In addition, decisions in December 2002 to proceed with the works for the breakwater at the Malamocco inlet and the first stage of the project for the protection of St Mark's square from high waters, and more recently on 3^rd April 2003 to go-ahead with the mobile barriers (so called MOSE system to defend the city of Venice from High waters) make the Venice in Peril initiative very timely. Furthermore proceeding with the mobile barriers is subject to certain specified conditions many of which are environmental in nature and the problems of Venice, associated safeguarding measures and other key environmental issues are of interest to other flood-prone urban locations worldwide.