Engineering Rome

Venice: the effects of water in the city

(Tabatha de la Rosa)

Introduction

The architecture, history, and picturesque canals of Venice have made the city one of the most popular tourist locations in the world. The influx of tourists, cruises, and the sea level rise threaten the integrity of the city. The combination of these factors has made the city candidate for Heritage in Danger by the UNESCO since 2016. Nevertheless, the city has proven to be resilient starting from how it was designed to the multiple modifications that have been through the years. This paper analyses: historical construction methods, the historical and current effects of motorized vehicles and sea level rise (SLR) in the city and the solutions the city is applying to combat them.

[image of canal]

Construction in Venice

Venice is situated in a lagoon, which are unstable locations, over time they are usually either covered by water or become land. In the case of Venice, it had three immediate challenges to overcome: soft soil, brackish water and shortage of land. Approximately, the first 70 m of soil are a heterogenous mix of artificial deposits, sand, clays, and silts. Due to this combination the soil on its own doesn’t have the capacity to withstand buildings taller than two stories. (Foraboschi). But Venice being one of the most prosperous cities of the 14th century attracted many newcomers and with the limited space available they needed tall buildings to accommodate its population. A combination of soil modification techniques and the addition of piles increased the strength and stiffness of the soil.

Although the modifications to the soil improved its capability to withstand weight, the buildings still needed to be lightweight. The buildings are made of brick with big windows/perforations, and the floors and ceiling are made from timber to minimize the weight. The issue with having such lightweight and thin walls is that they need stabilization. The Venetians used fiube to provide the extra stabilization these walls need. The fiuba is made from Istria-stone and connects the wooden floor to the walls through an iron hook. Figure 2 shows a fiuba with the visible hook, there are others that don’t show it, this is a stylistic choice. The fiube are commonly found in the buildings over the lagoon while are a rare peculiarity in mainland. Over time the buildings that needed extra stability were added sheer straps which serve the same purpose as the fiuba.

[picture of fiube and sheer straps]

Walking through the city, one can notice many buildings with a combination of fiube and sheer straps. While the fiube tends to have little variation across buildings, the sheer straps have a wide variety of shapes, sizes and placement across the different buildings.

Motorized boats and the city

Venice has served for years as a major port; it is the biggest one in the Northern Adriatic Sea with approximately 3500 port calls per year pre-pandemic. Ship traffic in shallow waters such as the ones in the Venice Lagoon can cause high leading waves, depression areas, or supercritical bores. These can damage the coastal environment and the integrity of the bottom. (Marco Scarpa, 2019).

[map showing ship routes]

Some of the effects described above have been intensified in the city after 1960s when the Malamocco-Marghera Channel (MMC) was opened. The major recorded effect is the erosion of the central lagoon between 1970 and 2000. Although negative effects in the lagoon have been registered and are expected to continue, there are plans for further expansion of the shipping port while restrictions are being applied to cruises which arrived through the Lido inlet, much closer to the city.

MOSE

[picture of the port]

One of the biggest threats to Venice is the SLR. Paintings by Canaletto among other artists have served as quantitative tools to understand the SLR by comparing the highly accurate paintings with the current sites. The traces of algae, the stillness of the water, and the many steps of the stairs used to get to the gondolas serve as clues into how the city has changed due to the SLR. Another clear and more recent indicator of the SLR is how buildings have closed what used to be their doors to access boats and made bridges or doors on what used to be their windows.

The city currently lies 80 cm above the sea level, while projections predict a SLR between 30 and 100 cm. To protect the city from the SLR, the city started the construction of the Mobile Venice Dams know as MOSE to try to control the water levels. The system extends for 1600 m and is made out of flap-gates. When there is a prediction of a high-water level, the gates are raised. This system is intended as a preventative measure with a lifetime of 100 years, although the system is still in construction.

Venice nowadays

Nowadays, Venice is in a complex position with tourism becoming its major and unique industry. This has made taking action to reduce the arrival of cruises and the use of motor vehicles particularly hard. It is estimated that before the pandemic cruises generated an average of 150 million euros per year (Daily Times). It wasn’t until July 2021 that the Italian government prohibited the arrival of big cruises to the Venice port. However, the law hasn’t been strongly implemented, combined with a decline of the cruises due to the pandemic is still unclear if the law will have an impact on the way tourism has been managed.

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