The $7BN Megaproject to Save Venice

[Music] this is the venice we're all familiar with and this is the version that's a little less ideal over time the city famous for its canals bridges and architecture has also developed a reputation for flooding yes it's always been prone to the water but the frequency and seriousness of its floods has gone up a few notches in recent years to solve the problem the city invested in a one-of-a-kind new defense system costing billions and featuring some amazing engineering its task is to stop this unwanted water problem once and for all but it's not gone entirely to plan far more expensive than first predicted and now decades in the making this game's been marred by corruption environmental opposition and questions about its long-term effectiveness in the face of a changing climate this is a story that any coastal city needs to hear and remember as we build the future both for its triumphs and its tribulations built in the middle of a lagoon venice has been susceptible to a natural phenomenon known as aqua alta or high water since its founding in the 5th century it's where a combination of weather factors take place at the same time a high tide low atmospheric pressure and strong winds blowing in from the adriatic sea the result is flooding and though it's been a part of life here for centuries it's now becoming an existential problem [Music] what used to happen just a few times a year began occurring more than 60 times a year by the end of the last decade and 2019 saw the worst flood in over 50 years with 80 of the city underwater combine this with rising sea levels more extreme weather events a city that's gradually subsiding albeit very slowly and bond james bond sinking buildings and you have a situation that needs an urgent fix that's where this near 6 billion euro or 7 billion us dollar flood blockade comes in now finally up and running 18 years after construction began called the mosaic system it's formed of 78 gates each 20 meters wide that rise up out of the water when flooding is imminent these pop-up barriers are located at three points along the coastal cordon that separates the lagoon from the adriatic the two lower inlets malamoko and kiyoja have one barrier each while there are two at lido in the north where a new artificial island fills the gap between them when they're not needed the gates are filled with water and lie in submerged giant reinforced concrete housings allowing boats to pass overhead to raise them compressed air is sent into the gates this forces the water out and causes them to rotate on their massive 42 42-ton hinges eventually breaching the surface once empty of water they form a barrier high enough to block even the highest tidal waters from getting through they can resist a three metre high tide that are designed to be effective even if sea levels rise by as much as 60 centimeters in the future once the tide passes the gates are refilled and they flip back to their closed position they can be raised in about half an hour and the sinking process takes about 15 minutes because each barrier has multiple gates and they can be controlled separately the whole system is flexible depending on the size of the tide and other conditions [Music] the way the gates work may be clever but it's the enormous housings or casings that are perhaps most impressive from a construction point of view these immense structures which are as big as apartment blocks and weigh many thousands of tons each had to be manufactured in three separate locations before being dropped into huge trenches on the seabed there are also two shoulder casings at all four barriers which connect the housings to the mainland these allow workers to reach the system's inner mechanisms via service galleries that run underneath each barricade at kiyoja and malamaco different methods were used to launch the casings into the water those manufactured on the kyoto side were constructed in a dry dock which was filled with water causing the finished structures to become almost buoyant barges armed with huge cranes were then used to pick up the casings and maneuver them to their resting place over at malamoko the units were moved by massive rolling platforms mounted on tracks once at the water's edge a crane lifted them in before barges and tugboats arrived to take them away across all three sites when it came to lowering the cases hydraulic dampers in each corner helps to absorb the force of these massive structures hitting the seabed even when mosaic is deployed there's still a way for vessels to get through locks were built alongside the barriers to ensure some boats could still come and go even when the gates are up it's a clever flood defense system that could also make a difference around new york city on san francisco bay or in sydney harbour in the years ahead but before these cities had the idea to basket it's important to ask a fundamental question does the system in venice actually work well the good news is it passed the first major test in october 2020 mosaic successfully protected the city from a 1.3 meter high tide and it's performed multiple times since but this doesn't mean that flooding's been stopped entirely in december it was unable to prevent an unexpectedly high tide from sweeping in and drenching the city once again but this wasn't the fault of the system weather forecasters underestimated how high the water would get so authorities kind of didn't think to switch it on [Music] it was far from the first blunder for the project in 2014 dozens of officials including the city's mayor were arrested in a corruption scandal with millions of euros in bribes thought to have changed hands over this game its final cost is now around 4 billion euros higher than originally predicted and that's without the 100 million euros required each year to maintain the system opponents have voiced their concerns about moses impact on the lagoon's ecological systems as holding back water in this way could lead to depleted oxygen levels this would get worse the more the barriers are used and it's likely they'll be seen more frequently as sea levels rise others have cast out over it actually being able to withstand the higher water levels that are expected to occur later this century the time it's taken has also been heavily criticized the system might be new but it was designed in the 1980s when attitudes to climate change were less serious than they are today many also question whether it's as effective as much older and less expensive defenses like the thames barrier in london or rotterdam system whether the pessimists are proved right or not this is what the people of venice are putting their faith in for years to come and for many it'll be a huge relief it might not turn out to be the perfect solution but the main thing is that it works at least for now and it stands as a powerful case study for other cities facing rising sea levels to look to if you liked this video and you want to 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Channel: Tomorrow's Build

Views: 2,736,072

Keywords: construction, architecture, engineering, Tomorrow's Build, tomorrowsbuild, TomorrowsBuild, tomorrows build, B1M, The B1M, Fred Mills, building, future, Venice, flood control, climate, sea levels, italy, flood defence, venice mose, climate change, new york, sydney, megaprojects

Id: b9_QDqpXCE0

Length: 8min 19sec (499 seconds)

Published: Tue May 25 2021