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POLICY FORUM: URBAN ECOLOGY
Flooding in Venice not only imposes high costs on those who live there but endangers a rich cultural heritage that is unique in the world. Scientists and engineers have not taken a long enough view in their approach to this serious threat. Records for the 20th century show that acqua alta, the local name for an exceptionally high tide, is a worsening phenomenon (1, 2). The decade with the highest number of such tidal events is the one that just ended. A project called MOSE (Modulo Sperimentale Elettromeccanico or experimental electromechanical module) was officially put forward in 1981 (2) as a potential answer to the problem. It would involve building a system of 79 mobile flood gates at the three inlets to the lagoon that surrounds the city.
This much-debated proposal has slowly worked its way through different review agencies (3-5), and the project has just reached the point where a final decision on its implementation is to be made by the Council of Ministers of the Italian government. However, new data on the long-term rate of rise in relative sea level (RSL) at Venice (6) are raising basic questions about the feasibility of the project. In light of the prospect of global warming (7), what is at issue is the high frequency of gate closing that will occur in the later stages of the gates' life and the impact that this will have on the ecology of the lagoon. The purpose of this article is to consider how science and public policy relate to one another at this critical juncture in the current effort to save Venice.
On 4 November 1966, Venice received an unexpected wake-up call in the form of a tidal event that peaked at 1.94 m above the standard for mean sea level established in 1897. The flooding took a heavy toll on the city's art and architecture and left many Venetian families with deep economic losses. This disaster drew worldwide attention to the vulnerability of the city. The tides themselves are driven by astronomical cycles in combination with meteorological conditions. Winds from the southeast, acting together with atmospheric pressure and rainfall, can produce storm surges reaching heights well above normal ones. To avoid flooding, the...