Saving Venice and other great plans to reclaim land from the sea26/08/2020
The ambitious MOSE project has implemented a mobile barrier system to prevent the Adriatic tide from flooding the Venice lagoon. Credit: Ihor Serdyukov.
ANTONIO LÓPEZ | Tungsteno
All civilizations have sought an enclave close to water to establish themselves, so perhaps it is not surprising that even back in Ancient Mesopotamia, Egypt or Rome, channels, reservoirs and dikes were built to manage inundations and river floods. This age-old challenge is now compounded by increasingly frequent droughts combined with extreme flooding and rising sea levels, two problems that require new solutions to preserve the habitability of hundreds of cities at risk of flooding. Looking to the future, large cities like New York, Miami and Jakarta, and even entire countries such as Bangladesh, are confronting the challenge of reclaiming land from the sea.
MOSE: the plan to prevent Venice from sinking
At this moment, one of the most pressing problems is the city of Venice, situated in the middle of a complex ecosystem formed by a lagoon connected to the Adriatic Sea. The system that supports the city has worked for 15 centuries; a structure of wooden piles and "waterproof" bricks keeps the foundations dry. But tidal fluctuations and rising sea levels are causing the city to slowly sink as the dry-humid environment that generates this constant alternation damages the clay bricks that support it.
The MOSE plan to save Venice includes the reconstruction of the coast and the environmental recovery of the lagoon, but the jewel in the crown to prevent flooding is a set of mobile barriers that block the seawater at high tide. A hydraulic system causes them to rise to the surface when the control centre considers it appropriate, as it monitors weather data to anticipate storms and tidal surges.
The 8-kilometer-long Oosterscheldekering dam is a unique work and the greatest exponent of the engineering feats of the Dutch Delta plan. Credit: Wikimedia Commons.
The Delta Plan: or how to turn water into dry land
With more than half of its territory at risk of flooding and 26% of it below sea level, the Netherlands would be a quarter smaller today if it had not engineered its way out of the water and into the sea.
Since the 12th century, the Netherlands has grown thanks to a system that involves draining the surface water, containing it with dikes and channelling it to the sea. Even the classic Dutch windmills were involved in the process by helping to drain the excess water. The worst flooding in its history, in 1953, gave rise to the Delta Plan: a comprehensive (and very ambitious) engineering solution to protect the land from water.
Today considered one of the seven wonders of the engineering world, the most formidable construction in this complex and specific network of gates, channels and dams is the Oosterscheldekering permeable barrier. With a length of nine kilometres, this structure of 65 pillars and 62 sliders avoids the need to completely close off the marine arm of the bay, which would have had dire environmental consequences. The complex hydraulic system of this flood barrier allows the gates to open and close when faced with tidal surges and storms.
To reclaim land from the sea using artificial islands is beginning to be an upward trend. One example of this is The World Islands complex in Dubai. Credit: Wikimedia Commons.
Growing by means of artificial islands
The system in the Netherlands is not the only solution for building in the water; artificial islands have become a trend in different regions of the world as a way to reclaim land from the sea. In 2015 alone, in China, the equivalent of two Manhattans of new land were created on a set of artificial islands constructed with a dredging system that uses ships equipped to suck sand from the sea bed and separate it from the water with a kind of blender, a centrifugal pump.
But the greatest example of this trend is a complex of more than 300 islands in Dubai, called The World Islands, conceived in 2003, although these types of island-building mega-projects have actually been going on since the 1990s. The first was Kansai Airport (in Osaka, Japan), located on an artificial island that required 21 million cubic metres of concrete to form the 30-metre-thick base layer on which it sits.
According to OECD forecasts, the engineering world will have to continue developing new construction tools in the battle against the sea, as it estimates that by 2070 up to $35 billion in real estate will be at risk of flooding in some of the world's largest port cities.
· — —
Tungsteno is a journalism laboratory to scan the essence of innovation. Devised by Materia Publicaciones Científicas for Sacyr’s blog.