The lagoon of Venice is one of the oldest examples of the complex relationships between human activities and natural dynamics. In the lagoon, the high tide phenomenon is particularly relevant and this causes periodic flooding in Venice and Chioggia. Rising water levels and gradual foundation decay started to be seen as a serious risk to the city and its people from the dramatic flood of 1966.

In 1973, the first Special Law Interventions to safeguard Venice was enacted, identifying the protection of the lagoon as an objective of national interest [1]. In the following years emerged the “Progettone” proposal, currently called MOSE. In 1984 the second Special Law for Venice emphasised the need for a unified approach to the safeguarding measures, set up the committee for policy, coordination and control of these activities, the "Comitatone"[see relevant government actors involved], and entrusted design and implementation to a single body, the Consorzio Venezia Nuova-CVN (constituted by major Italian construction companies and local cooperatives and firms). In 1998 the MOSE Environmental Impact Assessment received a negative opinion, but an appeal lodged by the Veneto Region to the Regional Administrative Court (TAR) annulled it. In 2001 the Legge Obiettivo was issued, an instrument creating a fast track to funding, project approval and execution of strategic national infrastructure. In 2002 the final design of the MOSE project was presented and in 2003, the Comitatone gave the go-ahead for its implementation. Works at the three lagoon inlets started the same year. The construction should be complete in 2016.

Starting from 2000 the project has met resistance from local citizens for high costs, environmental impacts and monopoly concession to CVN. In June 2005, the Permanent Assembly NoMOSE was founded with the aim to block the construction of the project. The Assembly promoted several forms of mobilization from information dissemination to popular petitions, demonstrations and work site occupations (2005). The later led to arrests among the NoMOSE activists in 2010. In 2005-2006, the Municipality of Venice, critical of some technical aspects of the MOSE system, commissioned a study [2] that proved technical failures of the project in situations of strong pressure from the sea and compared it with a new and alternative proposal [4]. But the new proposal was not considered. In 2005 the EU Commission opened an infraction procedure against Italy for "pollution of the habitat" of lagoon sites protected by the Nature 2000 Network and by the European Directive on birds. In 2009, after a few adjustments and given the importance of the project, the case was closed.

Local movement criticism against the project have dealt with various aspects. First the high costs for the Italian State for construction, management, and maintenance of the installations. The actual estimated cost for construction is 5,5 billion €. This exclude costs for management and maintenance whose details have not yet been established. The functioning will have a high energy cost, thus a power plant will be created on the artificial Island Novissima, situated between the mobile gates of the Lido inlet where control offices will be placed.

Then, the project affects the delicate and unstable hydrogeological balance and the unique ecosystem of the lagoon. The big monolithic infrastructure system is not “gradual, experimental and reversible” as required by the Special Law for Safeguarding Venice.

In addition, the local movement strongly criticized the Consorzio Venezia Nuova monopoly on the design, planning and implementation of any intervention on the city of Venice and its lagoon. Critics include the procurement assignments and the lack of transparency in the working procedure.

In June 2014 investigations of the Italian Judiciary led to the arrest of 35 persons (including the mayor of Venice, a former governor of the Venice region and the former President of the Consorzio Venezia Nuova) accused of corruption in connection with the procurement system of the MOSE project.

Compressed air will be pumped into the gates when a tide of more than 110m height is expected. The air will rise up the barriers to the surface of the water to block the flow of the tide and prevent water from flowing into the lagoon. When the tide drops, the gates are filled with water again and return to their housing.

The MOSE project also includes strengthening of the coastal areas, raising the quaysides and paving of the city.

The level of investment has increased considerably compared to the initial budget, from 3,4 to 5,5 bn €. The annual technical and energy costs for the operation of the Electromechanical system are unclear.