Operation of The Gates
MOSE consists of a system of retracting oscillating buoyancy flap gates which respects the indications given in 1982 by vote no. 209 of the Higher Council of Public Works, namely that the barriers must not modify water exchange between the sea and the lagoon to avoid damaging lagoon morphology and water quality, must not obstruct navigation, thus interfering with port activities and fishing, and must not alter the landscape. In normal conditions, the gates, large metal box type structures 20 m wide, between 20 and 30 m long and about 5 m thick, are full of water and rest in prefabricated concrete caissons on the reinforced seabed. When a tide higher than 110 cm is forecast, the gates are emptied of water by introducing compressed air. They therefore rise, rotating around the axis of the hinges until they emerge from the water, temporarily isolating the lagoon from the sea and stopping the tidal flow. The gates reach in the raised position in about 30 minutes and will then take about 15 minutes to retract.
The level of 110 cm above which the barriers will enter into operation has been agreed by the responsible bodies as the optimum level with respect to current sea level. However, the MOSE System is flexible enough to also be used for high waters below that level. According to the winds, pressure and level of the tide, the system can also be managed in different ways, with differentiated closure of the inlets or partial closure of each inlet.
A total of 78 gates divided into four rows will be installed to protect the three inlets: two rows of 21 and 20 gates at the Lido-San Nicolò inlet, the widest, connected by an artificial island; one row of 19 gates at the Malamocco inlet and one row of 18 gates at the Chioggia inlet. To guarantee navigation while the mobile barriers are in operation, three locks are being constructed to allow the transit of vessels (large ships at Malamocco, pleasure, emergency and fishing boats at Lido and Chioggia).
At the end of work, the consortium which has designed and constructed MOSE will be in charge of management and maintenance of the system for four years, then for a further 10 years it will be responsible for its operation and for all the other public works.
Read more about this topic: MOSE Project
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