BY STAS MARGARONIS, RBTUS
The City of Venice must to adopt “a resiliency plan to stave off the long-term threat of increased flooding and that flooding can come not just from high sea levels but also from the rivers and heavy rainfall,” according to Piet Dircke, a water management consultant for the Dutch firm Arcadis.
The resiliency plan needs to factor new construction and upgrades that raise roads, and walkways so as to “keep water from flooding transportation links and infrastructure including utilities, sewage, piping and bridges.”
Dircke, an internationally recognized water management expert, says the recent flooding in Venice makes the need for the resiliency plan more urgent.
He notes that the recent flooding in Venice was caused by an unusual combination of adverse weather patterns, that are likely to become more common for Venice and flood prone cities around the world as the intensity of climate change and sea level rise accelerate.
In the case of Venice, there “was an unfortunate combination of events”:
- Weeks of heavy rainfall.
- A high “King Tide,” in which the tide is higher than normal.
- A southeast wind blowing from North Africa that pushed water into Venice from the nearby Adriatic Sea that is called a Sirocco.
In addition, there has been a historic subsidence of land and buildings for many centuries “but this is almost coming to zero because of the ban on ground water extraction in Venice which has been addressing the problem.”
Unfortunately, “the sea level is rising, and this is posing a long-term threat to the city. The San Marco Square (in Venice) today floods more and more frequently.”
Fortunately, “people in Venice have become very resilient to what we would call ‘nuisance’ flooding. For example, stores continue to be open and restaurants continue to serve customers with waiters waiting tables in rubber boots sloshing around in the water.”
MOSE FLOOD GATE PROJECT
The Washington Post recently reported on the flooding in Venice in which it describes problems with the MOSE flood gate system that is supposed to protect the city but is still not complete. The newspaper said the rationale “behind the retractable gates was that, when they weren’t needed, they would allow Venice to retain its aesthetic feel, and allow for fishermen and other boats to make it in and out of port. More importantly, the Venice lagoon uses the Adriatic as a flushing valve, and its ecosystem would be jeopardized if sealed off from the high seas. But based on projections of rising sea levels, in the not-too-distant future the floodgates would need to be raised so often that they would function like a near-permanent wall.”[1]
Dircke notes that “the MOSE flood gate system is almost complete and will be able to protect the city from flooding in a range of 1.1 meters to 3 meters. This would have protected the city from the recent flood which was 1.8 meters.”
The MOSE flood gates require “78 gates for it to be completed and there are 9 gates that still have to be tendered. These should already been installed but corruption in the bidding process has caused a delay and included the jailing of the former Mayor of Venice.”
Dircke says the Netherlands is helping Venice by working through an organization called I-STORM, an international association devoted to building storm surge barriers, as well as with the Dutch national flood control agency Rijkswaterstraat “to help Venice develop the tender for the last 9 flood gates. This process needs to meet EU (European Union) bidding standards and to be very transparent. Once the bidding process begins there is going to be an additional 200 to 300 hundred million Euros that will need to be spent to complete the MOSE project with the last MOSE gates.”
Unfortunately, as a result of the delays a new discovery found that 6 to 8 of the first gates that were installed are corroded due perhaps to a failure to put on a sufficient coating. As all of the gates are permanently in the water, “the six to eight will need to be pulled out of the water, repaired and reinstalled into the water.”
People in Venice may be forgiven for believing “that there never is a light at the end of this tunnel and that the delays continue and continue.”
Dircke believes there is hope, but future sea level rise poses a long-term risk: “For Venice, the MOSE floodgates will be completed and working but nuisance flooding will continue to get worse and San Marco Square will face a growing number of days when it is flooded.”
THREAT TO HISTORIC BUILDINGS AND FROM ‘OVER TOURISM’
Dircke says there is a long-term threat to the older buildings in Venice: “As they continue to suffer from flooding, damage to older buildings will increase and is going to require a very expensive process of repair and protection.”
Another threat Venice faces comes from “over tourism that is coming in part from new cruise ship business that brings new money and new business to the city, but also places new stresses on traffic, pollution, water and will require some means to offset the damage that additional people are causing.”
[1] https://www.washingtonpost.com/world/europe/how-venices-plan-to-protect-itself-from-flooding-became-a-disaster-in-itself/2019/11/19/7e1fe494-09a8-11ea-8054-289aef6e38a3_story.html