How the Lagoon of Venice works, explained in six terms

Following the cruise ship accident of 2 June 2019, discussions were sparked on the future of Venice and a possible referendum on the new location of the port of Venice:

Six terms explain what works and what doesn’t for the Lagoon: There is no Venice without the Lagoon: Thus, any proposal regarding the port of Venice has to take six terms into account, outlined by Venetian engineers of the past (starting in the 11th century).

When you arrive in Venice, your first impression is the deep blue, turquoise green or grey water surface. This stretch of water, the Lagoon, is so much more than a “romantic backdrop”: Without the Lagoon fulfilling her tasks, Venice cannot exist. The Lagoon is the lifeline, which in Venice we call our liquid plain (pianura liquida). Any proposals for changes made to the Lagoonscape, from dredging canals to creating port facilities, need to take into account the following six terms described in the textbooks of the hydraulic experts of the past: Ghebo, barena, bocca, argine, escursione termica, Scanno della Pisciotta.

Ghebo (pronounce as “kebo”; plural: ghebi): The Lagoon is criss-crossed by a large number of narrow canals branching out into many directions. These canals are called ghebi, formed by marine and river currents. Their existence allows us to describe the Lagoon as living organism: Natural deep water canals can be compared to main arteries, but for the whole system to work and to supply all areas in the Lagoon with nourishment (plancton arriving from the open sea), the ghebi are indispensable.

Before the Lagoon was settled, there were four natural deep water canals following the river mouths. From these deep water canals, the numerous ghebi branched out to reach every part of the Lagoon. To this day, wooden poles called bricole / mede desig safe routes for boats. Sometimes, ghebi widen to create basins called sacche or secche, where in the past (400 – 1000 AD) saline (salt pans) were created.

Barena (plural: barene): Barene are sand banks overgrown with grass, sea lavender, and edible herbs while on velme (sand dunes) plants don’t grow well.

Barene are yellow-green swamps you can make out flying over the Lagoon. They act as sponges and soak up excess water (floods) and also purify the Lagoon from toxins. Thus, barene are essential in balancing the Lagoon ecosystem.

The barene fulfill their function during “normal times” but so far, the Lagoon experienced four major seaquakes. Also, the subsidenza (shifting ground) phenomenon causes islands to sink and others (re-)emerge. One example is the island Sant’Ariano in the northern Lagoon. These and the few times when the laws of the tides don’t apply are the only limitations when barene cannot do their work of protecting the ecological balance of the Lagoon.

Bocca di Porto (pl.: bocche; Inlets): Bocche are inlets between the outer Lagoon islands (Lido, Pellestrina) separating the Lagoon from the open sea, allowing sea water and nurishment (plancton) to enter the Lagoon. The depth of the inlets is decisive: The deeper a bocca di porta is (like dredged for cruise ships or oil tankers to pass), the more water will enter the Lagoon during high tide. The barene and the ghebi next to a deep bocca, having been dredged and removed, are unable to fulfill their task of soaking up excess water.

As a result, all the water masses reach Venice, as they aren’t stoppecd by the barene, causing acqua alta (floods) or even acqua granda (excessive floods) in the city. There were still five inlets in the 16th century, and it was the famous hydraulic engineer Cristoforo Sabbadino (1490-1560) who had two inlets closed in order to protect the Laguna viva (a term explained below) from turning into an arm of the sea.

Argine (pl: argini – dam): The next term we need to understand is argine, a dam following the watershed separating Laguna viva and Laguna morta. Yes, there are actually two Lagoons (!), remnants of the Lagoonscape which during Roman times was called The Seven Seas (I Sette Mari). As I’m explaining in this article, in the year 1610, the argine called Taglio Novissimo, was built to prevent the northern Lagoon (Laguna morta, consisting of freshwater pockets at the river mouths), from turning into an uninhabitable swamp. By building the dam, the hydraulic engineers of the Republic of Venice were able to prolong the life of the Lagoon, and the mix of flora and fauna required for human settlements was able to survive as well.

Escursione termica: Tidal patterns in the Lagoon work differently in summer and winter: Only one high tide per day occurs in summer, while there are two peaks in winter. When less water and nourishment arrive in the Lagoon during summer, the water level falls and temperature rises, which may endanger the survival of fish, birds and plant life. Thus, leaving the bocche di porto open to allow tides to arrive in the Lagoon is essential. The inlets cannot be closed without endangering the endemic flora and fauna. Escursione terminca is the reason why the Mose barriers, closing the Lagoon temporarily and repeatedly, could damage life in the Lagoon.

Maintaining the Lagoon ecosystem alive has never been easy during history. The above mentioned engineer Sabbadino warned against closing the bocche in the year 1555(!) as this would turn the Lagoon into a piscina (“swimming pool”): Plancton, the nourishment of fish, cannot arrive in the valli da pesca (fish farms), and the lack of sea water would be detrimental to animal and plant life in general. Sabbadino’s solution was to keep open three narrow bocche to ensure that just enough sea water and nutrients reach the Lagoon.

Scanno della Pisciotta: Until the 19th century, maps of the Lagoon show the existence of a large, banana-shaped sand bank off the coast of the Lido and the Cavallino Peninsula. This sand bank had to be carefully maintained to avoid blocking la bocca di porto del Lido. One can consider the sand dunes located on both sides of the bocca di porto del Lido as close “relatives” of the Scanno still visible in our times. And here, in the open sea off the Scanno della Pisciotta, the main port of Venice was located during the times of the Republic of Venice, until 1797.

Porto (port facilities): Using the Lagoonscape terms ghebo, barena, bocca, argine, we can describe the effects that dredging deep water canals, or creating a port facility, or closing the Lagoon by means of the Mose barriers, have on the Lagoon: Ghebi and barene are damaged, the bocche di porto need to be dredged, the argini removed, which impacts the watershed acting as barrier between the two Lagoons, Laguna viva and Laguna morta, and their different habitats.

Of course, striking a balance between protecting the Lagoon and the business interests of Venice was never easy. Until 1797, the business of the former Republic of Venice was based on transporting goods from the Levant to Venice and vice versa on board huge merchant cogs: The huge merchant cogs were never allowed to enter the Lagoon but were moored along Scanno della Pisciotta. Passengers and goods were taken to Venice (or rather, to the quarantine islands) on board smaller and flat vessels able to navigate the ghebi.

If you speak Italian and would like to learn more about the Lagoon, I’m sharing Governare le Acque, a video presentation by Professor Luigi d’Alpaos (Istituto Veneto and Università degli Studi di Padova), one of the most renowned experts in Lagoon hydraulics:

This blog post is Part 3 of Cruiseship Accident in Venice, 2 June 2019: Click here to read Part One: Cruiseship Accident in Venice: What Happened, the Background and the Future, and here to read Part Two: How Ships Damage the Lagoon, and What is Being Done: Expert Opinions.

5 responses to “How the Lagoon of Venice works, explained in six terms”

  1. Gary Francis Avatar

    It seems crazy that action isn’t being taken right now to provide a solution that takes the threats posed by the cruise ships away from the old city and provides real financial benefits for the city and its people from the thousands of day-trippers the cruise ships unleash daily.

    1. Iris Avatar

      There’s a huge backlog of tasks to fulfill and I agree, what you say is the core question to be resolved to ensure a sustainable future of our city.

  2. […] Click here to read the English version […]

  3. […] How does a Lagoon function, and six terms you must know about the Lagoon of Venice – read our blog article here. […]

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