All images © by Roberto Piperno, owner of the domain. Write to firstname.lastname@example.org. Text edited by Rosamie Moore.
When the Tiber grows
S. Maria sopra Minerva is one of the most interesting churches of Rome: its interior
contains masterpieces by Michelangelo, Bernini, Filippino Lippi and other important painters and
sculptors. It is also the church with the highest number (5) of papal monuments
after St. Peter's. Visitors usually pay little attention to its simple
fašade and do not notice a group of plaques on its right side.
The plaques can be divided into two groups of three: the upper group is composed of very similar plaques showing a hand pointing towards a stream of turbulent water: inscriptions in each plaque explain that the stream marks the level reached by the Tiber during floods which occurred in 1530, in 1557 and in 1598; the lower group of plaques have just an inscription indicating the level reached by the river in 1422, in 1495 and in 1870. The three higher plaques are considered as supporting evidence of the "European Little Ice Age", a period of lower temperatures and increased rainfalls which lasted approximately from 1500 to 1800.
The Tiber, unlike the other rivers of the Italian peninsula, runs parallel to the range of the Apennines mountains, where this veritable "backbone" of the peninsula reaches its highest points: M. Vettore (2476 m.); M. Terminillo (2213 m.), the "mountain of Rome"; Gran Sasso d'Italia (2914 m.), the "big stone of Italy"; M. Velino (2457 m.); M. Viglio (2156 m.); these mountains force the moist air coming from the Tyrrhenian Sea (some 50 miles to the west) to rise and eventually to cool and condense, producing local rain showers. When the ground is already saturated by previous storms, the rainfall is rapidly conveyed into the Tiber by small rivers on its left side. In particular River Aniene which flows through Subiaco and Tivoli and joins the Tiber near Ponte Milvio can grow in a massive way in a matter of hours.
All the main recorded floods occurred between the end of September and the beginning of January: winter months are usually dry and the occasional intense rainfalls which occur in April are unlikely to cause a significant increase in the river level because the ground is not saturated.
The ancient Romans emphasized the ship aspect of Isola Tiberina. Today the shape of the small island is modified by quays built to protect it, but when the river grows these modern alterations disappear and the island conveys again the impression of being a ship (by clicking on the link below the picture you can see an image of the same site when the river is at a low level).
Very occasionally someone falls into the river, either to commit suicide or because of drunkenness. A Police station located at the tip of Isola Tiberina is in charge of quickly assisting those in need and more in general of patrolling the river banks. Their boats are usually moored along the quays (click on the link below the picture to see them), but when the Tiber grows policemen tie the boat at the balcony of their small office. The picture on the right shows how the large opening at the centre of Ponte Quattro Capi easies the flow of water.
The last damaging flood of the Tiber occurred in December 1870, right after the annexation of Rome by the Italian State. Pope Pius IX called it a divine punishment for the sacrilege which had deprived the Church of its worldly possessions. The Italian government, more practically, debated at length on the best ways to protect Rome from further floods. Giuseppe Garibaldi, the national hero, strongly supported a project for deviating the river outside the Eternal City and turning its urban course into a canal (that is what happened to the Danube in Vienna), but eventually budget constraints led to a less dramatic plan. High walls along the river granted a physical protection to the lower quarters of Rome, but in addition to this the river bed was enlarged at certain locations which reduced the water flow. One of these bottlenecks was at Ponte Cestio: the buildings next to S. Bartolomeo all'Isola were pulled down and the two lateral arches of the bridge were enlarged.
In the XXth century several dams were built to exploit the energy of the Tiber and of its tributaries for hydroelectric generation; they have reduced the flood hazard and it is very unlikely we will ever see the Tiber flow through the "eye" of Ponte Sisto: in the past, when this happened, it announced a major incoming flood.
S. Maria sopra Minerva is not the only place where one can see plaques indicating the level reached by the river waters: Porto di Ripetta, S. Rocco, Arco dei Banchi and Ospedale di S. Spirito (to see the tablet placed by Pope Clement VIII click here) are other locations where floods are recorded. A less known tablet written partly in Latin and partly in Italian can be seen in Rione Regola, a quarter frequently flooded by the Tiber. In this rione, after the erection of the walls on the river, the level of some streets (which once led to its shores) was raised and this explains why one can see a fine Renaissance portal half buried in the ground.