MOSE Tide Barrier System
Modulo Sperimentale Elettromeccanico (MOSE) or Experimental Electromechanical Module is a protection project for the city of Venice, Italy and the Venetian Lagoon from flooding. MOSE: the system of flood barriers that has, after 1,200 years, allowed the floating city to withstand the rising sea levels. It is part of a General Plan of Interventions to safeguard Venice and the lagoon.
The project is an integrated system consisting of rows of mobile gates installed at the Lido, Malamocco and Chioggia inlets that isolate the Venetian Lagoon temporarily from the Adriatic Sea during “acqua alta” high tides. Together with coastal reinforcement, the raising of quaysides and the paving and improvement of the lagoon, MOSE protects Venice and the lagoon from tides of up to 3 m (9.8 ft). Currently it is raised for tides of more than 110 cm.
The name MOSE, before being the official acronym used to describe the entire flood protection system, represented the 1:1 scale prototype of a gate that had been tested between 1988 and 1992 at the Lido inlet. The name also holds another meaning: “MOSE” is a hint to the biblical character Moses (“Mosè” in Italian), famous for parting the Red Sea.
Concept
The Mose, 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 fashioned with 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 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.
While 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 compressed air is introduced into the sluices which empty it from the water.
As the water exits the sluice gates, rotating around 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, the lagoon and the sea water reaches the same level, 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 (LidoTreporti: 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).
Construction
Construction of MOSE was authorised by the committee (Comitatone) chaired by the President of the Council of Ministers and consisting of representatives of local and national Authorities and Institutions on 3rd April 2003. Work began simultaneously and continues in parallel at the three inlets of Lido, Malamocco and Chioggia.
Work on the structural parts (foundations, mobile barrier abutments and gate housing structures), associated structures (breakwaters, small craft harbours, locks) and parts for operating the system (technical buildings, plant) is now at an advanced stage.
Currently about 4000 people are employed in the construction of MOSE. Also, the construction sites at the inlets, fabrication of the main components of MOSE (the hinges, the mechanical nucleus of the system which constrains the gates to their housing and allows them to move, and the gates) is also in motion.
Restructuring of the buildings and spaces in the area of the Venice Arsenal where maintenance of MOSE and management of the system will be located is also underway.
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 marked by the shoulder boxes. They contain all the systems and buildings necessary for the operation of the sluice gates.
Works for what has been praised as a “jewel of national engineering” aimed at handling extreme situations began in 2003 and were envisioned to end in 2011. However, construction is now due to be completed in 2022, owing to delays and unexpected issues – like erosion, thanks to mussel.
With its specific composition for MOSE, it is able to guarantee a lifespan of more than 100 years.
To meet the high volumes required by the construction, Calcestruzzi has installed a concrete plant on the coast of the island of Pellestrina within the site area, consisting of 2 mobile plants. The cement produced by the cement plants in Calusco d’Adda and Trieste arrives at Porto Marghera and then reaches the concrete production plant directly by sea.
Facts
Four mobile barriers are under construction at the lagoon inlets (two at the Lido inlet, one at Malamocco and one at Chioggia).
The project utilises 1.6 km (0.99 mi) of mobile barriers.
There are 18 km (11 mi) of linear worksites on land and at sea.
MOSE has a total of 78 gates.
The smallest gate is 18.5 by 20 by 3.6 m (61 ft × 66 ft × 12 ft) (Lido–Treporti row).
The largest gate is 29.5 by 20 by 4.5 m (97 ft × 66 ft × 15 ft) (Malamocco row).
One lock for large shipping at the Malamocco inlet enables port activities to continue when the gates are in operation.
Three small locks (two at Chioggia and one at Lido-Treporti) allow the transit of fishing boats and other smaller vessels when the gates are in operation.
There are 156 hinges, two for each gate and a number of reserve elements.
Each hinge weighs 42 tons.
The gates can withstand a 3-m (9.8 ft) maximum tide (to date, the highest tide has been 1.94 m (6 ft 4 in)).
Mose has been designed to cope with a 60 cm (24 in) rise in sea level.
30 minutes are required to raise the gates.
15 minutes are required to lower the gates back into their housing structures.
During a tidal event, the inlet will remain closed for 4/5 hours, including barrier raising and lowering times.
References
https://www.designboom.com/architecture/ mose-flood-barrier-venice-storm-alex-10-05-2020/
https://www.mosevenezia.eu/project/? lang=en » https://edition.cnn.com/travel/article/mose-venice-flood-barriers/index.html
https://edition.cnn.com/travel/article/mose-venice-flood-barriers/index.html
By -
Tuhina Chatterjee, Associate Editor - Civil Engineering and Construction Review
