Venice: Keeping The ‘Floating City’ Afloat—For Now

Venice is under siege from a fast-rising sea, and a slow-to-complete mitigant. Will a new approach to lagoon isolation help or hinder efforts to keep the city above water?

While many industries have seen negative financial, regulatory and human knock-on effects from climate change, one industry has thrived: the climate change impact mitigation industry.

Rising seas have proved a particular challenge for cities on or near the water-edge, yet dams have remained the ubiquitous mitigant with little successful innovation over time. This post explores the business case for re-focusing industry efforts from innovation to improving defense resilience.

The Sinking ‘Floating City’

Venice is supported by more than 10 million multi-century-old wooden poles which hold up the foundations of its buildings.[i] These poles rest on a layer of hard clay and are sinking into the clay at a modest rate of ~2mm/annum.[ii] More worryingly, sea-level rates are projected to rise by ~8.6mm/annum through 2100.[iii]

To combat this, the Italian government has commissioned MOSE (translation: Experimental Electromechanical Module), a series of 78 barriers that will rise from the sea, blocking high waters from entering the lagoon’s three entrances.[iv] One lagoon will include a lock, to facilitate trade continuity.

Consorzio Venezia Nuova (CVN) is the pass-through company comprising the for-profit research, design and execution Italian-only companies responsible for MOSE.

Designing MOSE: Promoting Versatility

Traditional tide-mitigation barriers have focused on blocking an entire river-way or lagoon entrance(s), e.g., London’s Thames Barrier. However, this strategy presents a challenge for Venice, which as a historically important Freeport still accepts ~4,800 passengers arriving by cruise-ship per day:[v] how can you facilitate substantial sea trade while blocking increasingly frequent sea threats?

Slated for completion in 2018, MOSE is intended to strike this delicate balance, since the 78 barriers across lagoon entrances can be variously blocked, partially blocked or unblocked as befits the needs of incoming ships. Importantly, deep and wide cruise ships are accommodated since the barriers can be brought to the bottom of the lagoon inlets.[vi]

Designing MOSE: Sacrificing Resilience

This new and innovative solution is not without downsides. MOSE is designed to protect the city from seas of up to 286cm above current levels.[vii] The project was approved in 2003 using then-current forecasts, and unfortunately, the following decade has seen a doubling of estimations of the rise in sea-levels by 2100.[viii] Some expectations reach ~3-4x the annual rise vs. expectations just two decades ago.[ix]

At current average sea levels, a tide of 57cm leaves 2% of the city surface submerged, while 77cm (the intended threshold for raising the barriers) swallows 12%, and 135cm covers 80%.[x] The last fifty years have seen eight events of 80%+ surface-level submersion, with a max height above average of 194cm, and an average tide of 157cm.[xi]

Assuming a catastrophic event of 194cm-above-average tides and an increase in average sea levels of ~8.6mm/annum, MOSE’s protection period is ~105 years, roughly the intended usage timeframe at time of project authorization.[xii] Assuming sea increases of 13-14mm/annum shortens effectiveness to ~60-70 years.

Furthermore, since the infrastructure’s resting state is submerged, maintenance is more complex vs. above-water structures. Since rising sea levels correspond to a lower threshold for the MOSE operators to trigger the barriers, usage and maintenance requirements should increase. Performing maintenance on submerged structures is a key negative factor of MOSE, and current projections of sea level rises and subsequent barrier usage exceed what the structures were designed to be able to withstand.[xiii]

Next Steps for CVN’s Constituents

When considering sea-level assumptions and maintenance difficulties, many scientists now believe that MOSE’s effective use period will be limited to decades.[xiv] [xv] Likely as a consequence, MOSE Project has since been expanded to include non-barrier-based elements such as raising the height of Venice’s quaysides. The project’s extension has been branded “Not Just MOSE.”[xvi] In part due to these extensions, costs have escalated from ~€4.1bn to ~€5.5bn.[xvii] [xviii]

My recommendation for CVN’s constituents is to acknowledge the deficiency in planning for versatility vs. resilience. When considering future projects, planning for resilience must be the primary objective, with all local elements and commercial biases taking a back seat. This may be a short-term negative for many involved—more expensive structures lead to higher government costs and local taxes, while lower design flexibility leads to less competitive differentiation between construction companies. However, the MOSE Project clearly exhibits the pitfalls of overlooking a primary objective for the sake of a secondary objective; it would be ill-advised to repeat this process.

(709 words)[xix]



[i] Eric Nakasako, Illumin, vol. X, no. IV (July 2008),, accessed November 3, 2016.

[ii] Science Channel, “Sinking City—Venice,”, accessed October 31, 2016.

[iii] US Department of Commerce National Ocean Service, “Is sea level rising?”, accessed November 2, 2016.

[iv] MOSE Project, “MOSE System,”, accessed November 1, 2016.

[v] Port of Venice, “Passengers,”, accessed November 3, 2016.

[vi] MOSE Project, “MOSE System”.

[vii] MOSE Project, “MOSE System”. 286cm at current levels = 300cm at 2003 levels.

[viii] US Department of Commerce, “Is sea level rising?”

[ix] Center for American Progress Action Fund/Think Progress, “Has The Rate Of Sea Level Rise Tripled Since 2011?”, accessed November 2, 2016.

[x] City of Venice, “The altimetry of the historical center: percentage of flooding,”, accessed November 3, 2016.

[xi] City of Venice, “Data & Statistics,”, accessed November 3, 2016.

[xii] City of Venice, “Venice Altimetry,”, accessed November 3, 2016.

[xiii] City of Venice, “Venice Altimetry.”

[xiv] World Bank, “Climate Resilient Cities,”, accessed November 3, 2016.

[xv] Steve Connor, “Venice flood barriers scheme ‘will soon be obsolete,’”, accessed November 2, 2016.

[xvi] MOSE Project, “Not Just MOSE,”, accessed November 1, 2016.

[xvii] MOSE Project, “MOSE System.”

[xviii] IlFattoQuotidiano, “[trans.] MOSE, in ten years, costs [€]1.3 billion more,”, accessed November 1, 2016.

[xix] Photograph credit: MOSE Project, “MOSE System.”


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Student comments on Venice: Keeping The ‘Floating City’ Afloat—For Now

  1. Raphael, thanks for an interesting post. Cities all over the globe have expensive projects underway to mitigate the effects of rising seas on their coastal infrastructure. As you point out, it is entirely possible that current forecasts will be wrong, and the useful life of the improvements could actually be much less than was anticipated when they were capitalized. There is certainly a case for conservatism in the useful life forecasts of these types of projects.

    Your post also made me think differently about the costs associated with climate change. Most people (myself included) gravitate toward thinking about the costs of increase pollution, severe weather, and rising seas. But there are certainly business opportunities in climate change too. Just ask the heavy equipment contractors paid millions to clean up record snowstorms across the northeast this winter.

  2. Great article. It’s great that they finally managed to finish the barriers after years of delays. I’d be curious to hear your thoughts on allegations that the project will alter the biodiversity of the lagoon (

  3. Great article! Unsure of one thing though: Does these 78 mitigation dams simply keep the high water waves from entering into the harbor or do they keep all of the rising water out? At the end of its service life will it effectively be holding back meters of water?
    Another random thought, as the buildings were already on poles, did they consider the cost of ‘re-raising’ the buildings to a new higher level?

  4. Raphael; thanks for this interesting post on such a life-or-death issue for the city.

    I thought your discussion of time-frames and useful lives was particularly interesting. So far in business school, we’ve been discounting future states and future investments–with the effect that things occurring more than, say, 30 years in the future have little impact on decision-making today. This likely isn’t the right framework to use for civil engineering projects like this one, though. Of course it matters whether Venice sinks in 35 years!

    I’d be curious to learn more about what kind of future-state discounting is appropriate for this type of decision making.

    Thanks Raphael!

  5. Raphael, thanks for the thoughtful and interesting post. I wonder if there are other examples of cities or countries approaching this same problem of rising seas in a different way. Certainly, this will be an important and necessary ‘playbook’ for many more cities and countries. Venice may in fact be lucky, as they can focus on the lagoon entrances. Islands that are at risk face a trickier task.

  6. This was a very enjoyable read. While I’ve heard in passing of this project before, I didn’t know about all the negative implications the project had in terms of impacting the way & quality of life for Venice. What I find even more interesting after reading this is the fact that after so much time, energy, and effort was put into planning and developing MOSE, climate change is happening at such a rapid pace that its useful life will be much shorter than originally intended.

    With that in mind, while I do agree with your argument that they should have planned more for resilience, I also wonder if they should take a more active role in combating climate change in general. Islands in the Pacific are facing similar issues as Venice but with less resources. They have accepted the fact that building seawalls is a reactionary measure and will only do so much to save their coastal cities short of moving them entirely [1]. Their plea to the rest of the world is to step up, take responsibility, and take meaningful action and with Italy in the EU, it’s in a unique position to help make that influence in the EU.

    [1] –

  7. This post hits particularly close to home as a few of my family members are Venice residents. I have seen this initiative “in action” over the past few years when I visit the floating city. I agree with you that they should acknowledge their mistakes in this case and not let this happen again. Unfortunately, Venice will be quite hard to salvage. So much of the economy there is driven by tourism and putting up gates to prevent the sinking will prevent cruise ships and other tourism to easy access the city. There is a serious trade off here. Hopefully other floating cities can use Venice as an example of what not to do when implementing these programs. I would be interested to understand other use cases of similar programs and if/how they were implemented.

  8. Rapha – interesting and (as always) entertaining. When I last visited Venice, residents seemed to be of two minds: (1) the sink is inevitable so enjoy it while we have it or (2) it’s time to leave. I am curious your take on why residents are so fatalistic when MOSE can help the city accommodate. Perhaps, it is because of the tension you highlight around versatility vs. resilience. There is even a xenophobia-fueled but likely-warranted response around worries that visitors are contributing to the problem ( I guess what intrigues me most is how citizens react when their government have a plan but they don’t buy it.

  9. Great Article. Would I be correct in assuming the expansion in scope of the MOSE, and consequent spiraling costs, is an attempt to address the acceleration in sea-level increases vs. initial forecasts? If so, how are residents responding to the growing threat? Have there been any alternative proposals to address any further unanticipated forecasts in the future?

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