Case Study 4: MOSE flood barrier in Venice, Italy

Although the threat is different from that in the case of the Thames Barrier, like London, the gated flood defenses of the MOSE project in Italy are designed to protect Venice from high tides and surges from the Adriatic Sea, thereby reducing flood frequency. The project takes advantage of the three main tidal inlets connecting the Venice lagoon to the sea, where a series of hollow gates on hinges initially resting on the bed will rise and close the inlets during periods of high tides. The MOSE barrier uses a completely different method than the approach used in the Thames Barrier. The idea, however, is similar in that for much of the time, when there is no imminent threat of flooding, the gates are filled with water and resting on the sea bed; when floodwaters threaten Venice, the gates are closed in response to incoming high water. The smart building elements in this approach are in the design, the operation, and the utilization of processes and water properties to minimize operating costs, energy, and maintenance. The gates simply close under the influence of gravity by slowly filling up with sea water, and once fully open the added weight of the steel when added to weight of water keeps them submerged. To close the gates, the opposite of gravity, buoyancy, is used. Pumped air forces water out of the gates, and since the air density is more than a thousand times less than seawater, the gates are lifted into the closed position, rising above the water surface. The lack of mechanical infrastructure and arms to perform these steps keeps operating cost low, although, as we learned in earlier modules, the upfront capital costs for such projects can be in the billions of dollars.

Watch this video flood gate demonstration