Page 3 - monument

THE FLOODS OF THE TIBER
The Tiber, even if it had given birth to Rome, periodically created some pro- blems: the floods.
On average, every 20 years an "important" one (+17 meters) has arrived and every 200 one with catastrophic effects (+19 meters).
Numerous plaques, called little hands, are scattered throughout the city and indicate the levels reached by the water in the various neighborhoods.
In ancient times and during the Middle Ages, the only contrasting action was to raise the ground, where possible.
To get an idea of the phenomenon, just think that the Thames or the Seine increase their range by 6, 7 times when exceptional events occur. The Tiber 35 times!
But in 1870, just 3 months after the conquest of Rome by the Italian army, a devastating one arrived and then, the new government was forced to find a definitive solution.
Numerous solutions were proposed and among these also the one, sugge- sted by Garibaldi, to create a bypass that went around the city.
The final decision was to build containment walls.
The project was ready in 10 years but their complete realization had to wait until 1926: 45 years later. And, meanwhile, the floods continued: the photo below is from 1900.
In 1937 a flood of +16.8 m arrived and the walls worked perfectly!
The map above shows us the areas that were flooded during the flood of 1870.
As you can see, the flooded areas are sometimes not contiguous. This is because of the water whi- ch, going through the sewers in reverse (in our case the Cloaca Maxima), brought the same level of the river back to the city as well.
To solve this problem, all the sewers were made to flow into two large collectors inserted in the walls that pour the waters at the end of the city.