With some 300,000 people living and working in a danger zone that measures some 1,135 hectares, Rome has “the highest exposure in Europe” to the risk of flooding, the Central Apennines District Basin Authority said on Monday.
“There are parts of Rome that can't withstand a heavy downpour,” according to the authority, which monitors the risks of floods, landslides, coastal erosion and other water damage in and around the Lazio region.
Rome's soft soil and famous hills make it naturally vulnerable to erosion and mudslides. But in its latest report, the authority said poorly maintained sewers, waste dumping and rampant vegetation blocking the course of the Tiber and Aniene rivers were contributing to the danger.
It has identified nearly 400 areas in the Rome area that are considered at risk of landslides, especially Monte Mario, the city's highest hill, Viale Tiziano near the Parco della Musica concert hall, Monteverde Vecchio by the Villa Doria Pamphili park, and the Balduina neighbourhood in the north-west.
The swollen Tiber in December 2008. Photo: Protezione Civile/AFP
Rome is further weakened by several kilometres of cavities running underneath the city, some manmade in previous centuries and others the result of subsidence.
At least 32 square kilometres of underground caverns have been mapped so far, while the number of new holes opening up is increasing at an alarming rate, the authority said: more than 90 sinkholes appeared in Rome each year on average in the past decade, compared to just 16 a year between 1998-2008.
A massive sinkhole opened in the Balduina neighbourhood in 2018. Photo: Tiziana Fabi/AFP
Rome's problems have been clear to see in the past month as weeks of rain fill drains and send the overflow spilling into the streets. Several roads were left underwater after the heaviest storms.
The city last suffered heavy flooding in January 2014, when downpours flooded the streets and brought public transport to a halt.
While high walls protect the heart of Rome from the Tiber, the river has burst its banks outside the historic centre at least three times since 2008.
Firefighters in the Prima Porta suburb north of Rome in January 2014. Photo: Tiziana Fabi/AFP
Cities are the parts of Italy most at risk from extreme weather aggravated by climate change, according to a recent report by Italian environmental watchdog Legambiente.
And of all Italian cities Rome suffers the highest number of extreme weather-related events, the report found, with 33 during 2018.