How the Lagoon of Venice Works, Explained in Six Terms

Click here to read the Italian version 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 and Venice. There is no Venice without the Lagoon: Thus, any proposal regarding the port of Venice has to take six terms into account, used by Venetian engineers since the 11th century.

When you arrive in Venice, your first impression is the deep blue, turquoise green or greyish water surface surrounding the city. This stretch of water, the Lagoon, is so much more than a “romantic backdrop”: Without the Lagoon fulfilling her tasks, Venice cannot subsist. Thus, to Venetians, the Lagoon is the lifeline, the liquid plain (pianura liquida). Any proposals for changes made to the Lagoonscape, from dredging canals to setting up 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 not just one water mirror but her ground 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 responsible.

Before humans settled in the Lagoon, there were only ghebi branching out from four natural deep water canals following the river mouths. So yes, from the beginning, it was difficult and often dangerous to navigate the Lagoon. To increase safety, wooden poles called bricole / mede designed the safe routes for boats. Sometimes, the ghebi widened to create basins called sacche or secche, used during early Venetian history (400 – 1000 AD) to set up saline (salt pans).

Barena (plural: barene): Barene are sand banks overgrown with grass, sea lavender, and edible herbs (compared to sand dunes which don’t host plants). Often, it’s hard to distinguish between what is a barena and what is actually an island!

Barene are the yellowish-green formations you can make out flying over the Lagoon. They act as sponges and are able to soak up excess water (floods) and purify the Lagoon from toxins. Thus, barene are essential to balance the Lagoon ecosystem, but is this really possible over time? Yes, but there are exceptions: So far, the Lagoon experienced four major seaquakes. Also, the natural subsidenza (shifting grounds) 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 thus nurishment in the form of plancton, to enter the Lagoon. Their depth is of vital importance: The deeper a bocca di porta is (like dredged to let cruise ships or oil tankers 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 arrives directly in Venice, causing acqua alta or even acqua granda (floods). 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 (see below) from turning into an arm of the sea.

Argine (pl: argini – dam): The next term we need to understand is argine, the 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. In this way, the hydraulic engineers of the Republic of Venice were able to prolong the life of the Lagoon, and the exact mix of flora and fauna required for permanent 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 arrives in the Lagoon during summer, the water level sinks and temperature rises which may endanger the survival of fish, birds and plant life. Thus, leaving the bocche open to allow tides arrive in the Lagoon is vital.

Escursione terminca is the reason why the Mose barriers, closing the Lagoon temporarily and repeatedly, have the potential of damaging life in the Lagoon: Maintaining the Lagoon ecosystem alive has never been easy during history. The above mentioned 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 just three narrow bocche to ensure just enough water and nutrients arrive in 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 obstructing la bocca del Lido. You can consider the sand dunes located on both sides of the bocca as closest relatives of the Scanno still visible in our times. And here, in the open sea along the Scanno della Pisciotta, the port of Venice was located during the times of the Republic of Venice, until 1797.

Porto (port facilities): Based on the Lagoonscape terms above, ghebo, barena, bocca, argine, describe the effects that dredging deep water canals, or creating a port facility, have on the Lagoon: Ghebi and barene are destroyed, 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 the Republic of Venice was never easy. Business was based on transporting goods from the Levant to Venice and vice versa on board huge merchant cogs: These 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.

Italian Version coming soon

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  1. 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. 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.

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