The Venice Lagoon and the three inlets
How the Mose System works
Barrier: type section and construction elements
The gates emerged in the North Lido inlet
The Mose system is located at the inlets of Lido, Malamocco and Chioggia, the three gates of the coastal cordon through which the tide spreads from the Adriatic sea into the Lagoon. To respond to the objective set by the Law for Venice 798/84, the complete defense of the entire lagoon from the high tides of any level, an integrated system of works has been developed that foresees the barriers of mobile gates, able to isolate the lagoon from the sea during the events of high tide, complementary works such as the cliffs outside the port mouths, designed to attenuate the levels of the most frequent tides and the rise of the banks and pavements, at least up to +110 cm, in the most low in the lagoon dwellings. The integration of these interventions defines an extremely functional defense system that guarantees the quality of the water, the protection of the morphology and the landscape, the maintenance of the port activity.
The Mose is formed by a series of barriers consisting of mobile gates located at the inlets. There are 4 defense barriers: 2 at the inlet of Lido (the one closest to Venice which is twice the size of the other two and is made up of 2 channels with different depths) which are respectively composed of 21 gates and one in the north channel of 20 that in the south channel, the two barriers are connected to each other by an intermediate island; 1 barrier formed by 19 sluice gates at the port mouth of Malamocco and 1 barrier of 18 gates at the port mouth of Chioggia. The depths and pre-existing sections of the mouth canals are not altered by the work. At the port mouths of Lido and Chioggia, take shelter and small navigation basins allow the admission and transit of pleasure boats, rescue vehicles and fishing boats even with the sluice gates in operation. At the mouth of Malamocco a navigation basin was built for the transit of ships, so as to guarantee the operation of the port even with the sluice gates in operation. The basin, protected by the outer cliff that creates a calm water basin sheltered by the waves, is located on the south bank of the mouth and has a useful length of about 370 m and a width of 48 m. The cliffs to the south of the port mouths, requested by the Council of Ministers on 15 March 2001 and the Steering, Coordination and Control Committee of 6 December 2001, serve to dampen the liveliness of tidal currents at the mouths attenuating the most frequent tidal levels. The cliff outside the mouth of Malamocco also has the function of creating a basin of calm waters that facilitates the entry of ships into the navigation basin, to the sluice gates.
Operation and construction elements
When they are inactive, the floodgates are full of water and lie completely invisible in housings placed in the backdrop. In the event of a particularly high tide hazard which could cause flooding of the territory, compressed air is introduced into the sluices which empties it from the water. As the water exits the sluice gates, rotating around the axis of the hinges, they rise up to emerge and block the flow of the incoming tide in the lagoon. The sluice gates remain in use only for the duration of the high water event: when the tide falls, and in the lagoon and the sea the same level is reached, the sluice gates are again filled with water and come back into their own premises. Each gate is made up of a metal box-like structure bound by two hinges to the housing box. Each gate is 20 m wide and has different lengths proportional to the depth of the mouth channel where it is installed (Lido-Treporti: 18.6 m and Malamocco: 29.6 m) and variable thickness (Lido-Treporti: 3.6 m and Chioggia: 5 m). The average closing time of the port inlets is about 4/5 hours (including the maneuver times for the opening and closing of the sluice gates).
The housing caissons are the elements that form the basis of defense barriers: they house mobile sluice gates and systems for their operation. They are connected by tunnels that also allow technical inspections. The connecting element between the barriers and the territory is represented by the shoulder boxes. They contain all the systems and buildings necessary for the operation of the sluice gates.
The need to defend the lagoon territory from increasingly frequent and intense high water is the origin of the design of the Mose system, whose subsequent realization, currently underway, may also be an opportunity for a comprehensive exploitation of the territory. The Venice Water Authority, prescribed by the Ministry of Cultural and Environmental Heritage as expressed in the Safeguard Commission, instructed the University of Architecture in Venice to carry out the preliminary project for the insertion of the defense works from the high waters into the landscape of the Venetian coasts. For each inlet, a proposal of intervention has been elaborated whose guidelines can be summarized in the necessity to maintain unchanged the character and the perception of the places; in the enhancement of the environmental, landscape and historical complexity of the coast; in the improvement of their practicability and functionality.