The Problems of Acqua Alta and the False Expectations of Mo.S.E.


versione italiana

The first autumn acque alte have arrived, with a sequence of days – in the second part of last week – of sustained tides, between 116 and 125 centimeters at the mouth of Lido harbor. The floodgates were raised, and rows closed, yet the flooding of Piazza San Marco was noticeable, and the water invaded the banks in several “lower” parts of the city.
The situation is again creating difficulty for residents and businesses, especially in the Marciana area. Marco De Martin, director of a boutique in the Procuratie Vecchie, wrote a letter to Mayor Luigi Brugnaro in which he asks “what is the point of raising Mo.S.E. at times when there will still be water in San Marco”. “It often happens to allow the passage of ships, but if the naval part is more important than safeguarding that is not ok”, says De Martin to Corriere del Veneto. “If you tell me that Mo.S.E. is going to be raised, I expect to find the whole city dry”, adds Claudio Vernier, president of the Associazione Piazza San Marco.
On Thursday there were also inconveniences regarding the footbridges. After the moment of peak tide Veritas ordered them to be removed as usual. However, around 16:00 people continued to walk on them, finding gaps between one footbridge and another.

In a letter sent to the local press, Prof. Andreina Zitelli, a former member of the Environmental Impact Assessment Commission (VIA) and responsible for drafting the negative VIA Opinion, highlights these and other problems, which are inherent – as well as widely and repeatedly stigmatized over time – to the Mo.S.E. project itself and its realization.

The text of the letter follows:

Mo.S.E. is not designed to intercept the low/medium tides that are and will always be the most frequent.
Having made the citizens believe (and businesses in particular) that Mo.S.E. is a system for combatting all high tides represents not only a technical error but also false public information. False information generates mistaken expectations and implies the dismantling of the alert system (sirens, notices, footbridges) and the installation of individual safeguards (high shelves and gates at the front door).

One of the reasons for the negative Environmental Impact Assessment (VIA) of Mo.S.E. (1998) was that the system of dams could not serve to regulate low, medium and medium-high tides. 

Moreover, low and medium tides (from +90cm to +130cm) cannot be classified as “exceptional”, that is those against which the system of interception is provided for in Law 798/84. Mo.S.E. cannot be used to intercept small tides because it was simply not designed for this.

In addition to creating expectations and the dismantling of defense systems, the uncertainty of forecasts leads to false alarms and closures. The frequent closures then interrupt the life-giving exchange between the sea and the lagoon and compromise navigation to the port.

These considerations, along with others relating to the behavior – still unknown and unpredictable – that the dams could exhibit when faced with serious marine disturbances of exceptional magnitude, led to the negative Assessment of Mo.S.E., inviting a review of the methods of intervention due to the environmental and climatic complexities that determine the phenomenon of “acque alte” and their logistical consequences for the city and businesses.

Translation by Paul Rosenberg

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The Problems of Acqua Alta and the False Expectations of Mo.S.E. ultima modifica: 2023-10-23T16:53:00+02:00 da ANDREINA ZITELLI
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