Venice, Italy, is a city famous around the world for not only its stunning canals and historic buildings, but also for its high vulnerability to flooding. The MOSE system of mobile flood barriers is a bold initiative intended reduce risk, preserve the cherished cityscape, and protect the entire Venice Lagoon from flooding.
Based on information from the project website
The MOSE (short for “Modulo Sperimentale Elettromeccanico” in Italian) system consists of four mobile barriers closing off three inlets in the Venice Lagoon. The barriers themselves are made up of 78 flap gates that are installed at the bottom of the inlets to separate the lagoon from the sea when raised. The system takes approximately 30 minutes to open and can be closed in 15 minutes, but takes on average five hours to close. Once raised, the barriers are able to withstand three meters of high tide. The barrier at the Malamocco inlet even has a lock system installed to allow merchant and industrial ships to cross while the MOSE system is in operation to reduce interference on port activities.
Seasonal high water is a constant threat to Venice, and the city has adapted with raised walkways, waterproofed buildings, and power outlets installed halfway up the wall in businesses and homes. Flooded scenes of a usually picturesque St Mark’s Square can be explained due to the fact that it is the city’s lowest point. However, more extreme high tides that occur roughly every three years and can raise water levels by over a meter present a much greater risk to Venice’s cultural heritage and justify a system such as MOSE.
Venice and its Lagoon is a UNESCO World Heritage Site, which makes its protection even more important. The MOSE project was implemented by the Italian Ministry of Infrastructure and Transport and managed by the Consorzio Venezia Nuova for the purposes safeguarding Venice and the lagoon. The decision to construct the mobile flood barriers was made after collaboration between all levels of government and consideration of various other coastal defence measures.
The MOSE system in its entirety is an impressive and innovation response to the threat of coastal flooding and erosion, both from a construction and coordination standpoint. The hydrological and geophysical profile of the Venice Lagoon needed to be fully considered when designing the barriers and their final locations.
While the MOSE Control Centre uses advanced technology to predict flooding, model the effects of gate manoeuvres, predict port traffic, determine warning levels, and so on, the MOSE project also employs other smaller scale measures to optimise the overall goal of flood risk reduction in the lagoon. These local defences consist of raising quaysides, roads, walkways, and installing smaller gates in the urban canals in the lagoon settlements, known as the “Baby MOSE” gates. This holistic and comprehensive approach to encouraging protection for the entire lagoon, aside from that which is provided by MOSE, is also innovative.
It is not easy to construct such large-scale defences in fragile environments, but, as the MOSE system illustrates, sometimes this approach is necessary to provide significant long-term protection. Venice represents an especially vulnerable coastal city with globally significant heritage sites and a very active tourism industry. With so much at risk, the MOSE system will ensure businesses, residents, and visitors will be able to enjoy the fabled canals, palaces, and plazas without the threat of flooding and building damage. The implementation of local defences diversifies the resilience of the settlements in the lagoon and increases the rate of success for the MOSE project.