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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Gronda lagunare | 4/6 | https://en.wikipedia.org/wiki/Gronda_lagunare | reference | science, encyclopedia | 2026-05-05T07:18:21.567680+00:00 | kb-cron |
=== The "stiffening" of the gronda lagunare === In Italian the term "stiffening" of a shore or bank refers to the construction of embankments. Such works create rigid structures which make the shore or bank rigid compared to a natural state and constrains its waters. The term comes from the word rigido, rigid. In relation to the gronda lagunare, it indicates the development of artificial shores along the gronda and, through this, the creation of a fixed lagunar boundary which prevents natural fluctuations of its edge with a consequent loss of gronda's character as a transitional area between the open lagoon and the mainland with lagunar deltas and wetlands. Much of the gronda lagunare has been "stiffened" by the above-mentioned river diversions carried out by the Republic of Venice (particularly with the Taglio del Sile, Osellino and Taglio Novissimo canals). It has been accentuated by 20th century developments. This situation started to draw attention in the 1970s, when scientists determined that this exacerbates the risk of flooding in Venice and elsewhere in the lagoon. The river delta which was created in the southern part of the lagoon by the Brenta Nova canal and the nearby areas saw extensive land reclamations in the early 20th century. This dramatically changed the characteristics of this area, wiping out the local saltmarshes and patches of the lagoon and completely rearranging the local lagunar hydrographic network. It triggered substantial subsidence, causing in the long-term a lowering of the ground by a few metres. A new airport, the Venice Marco Polo Airport, was built by the edge of the central part of the lagoon, in the Tessera area in 1961. Its 3.3-kilometre (2.05 miles) long runway runs along the coast of the lagoon. The airport was built over part of the Osellino canal (which was covered), some 500 metres before it ends in the River Dese. The central area of the lagoon has been affected by industrial development. In the 1950s the town of Marghera, on the mainland coast of the lagoon, started to become an industrial area. The digging of a canal, the Malamocco-Marghera canal, was proposed. Its purpose was to link the Malamocco inlet access of the sea into the lagoon to a second industrial zone at the port of Marghera and make it accessible to large ships. With the development of large oil tankers in the 1960s, the project was modified and the canal was dug to a greater depth to allow these vessels though. For this reason the canal was nicknamed canale dei petroli (oil canal). The works started in 1964 and finished in 1968. An oil refinery was also built. The sediments which were dredged to create the Malamocco-Marghera canal were used to create artificial islands, the casse di colmata A, (155 hectares), B, (385 ha) and D-E (752 ha), for the creation of a third industrial area at the port of Marghera. The original plan envisaged further artificial islands that would fill in the whole of the saltmarsh area between Marghera and Chioggia, in the southern part of the lagoon. However, studies carried out by scientists after the disastrous 1966 flood in Venice and the lagoon showed that the islands reduced the area in which the tidal flow could expand and that this had an impact both on lagoon's water level and the efficiency of water turnover in the lagoon. The former has also had the consequence of worsening the aqua alta phenomenon (high water, the floods which can occur in Venice and the lagoon with above average high tides). As a result, the expansion works were suspended in 1969 and the plan was scrapped in 1973. To try to alleviate these problems a number of channels which had been filled in to create the islands were reopened to reconnect the waters behind these islands to the rest of the lagoon. These are the Volpego and Fiumesino, which cut through the cassa B, the Taglio Vecchio and Mattoni, which cut through the cassa B and the Avesa, which cuts through the cassa A. The area of the lagoon which can absorb the tidal flow has decreased by about 30% since 1791. The "stiffening" of the gronda lagunare, which has been worsened by the creation of the artificial islands for the industrial area, and its connection with an exacerbation of the aqua alta phenomenon has also drawn attention to another factor which contributes to this "stiffening" of the gronda lagunare: the valli da pesca with fixed banks.