Seine flooding: study reveals that 70,000 Parisians in the same neighborhood would be the first to be affected

A new study published on June 1, 2026 by the Institut Paris Région (IPR) draws an alarming conclusion. In the event of flooding of the Seine, over a million Parisians would be directly threatened by flooding. Paris and its inner suburbs appear to be the most vulnerable areas inthe Paris region.

More than 555,000 homes at risk of flooding

The IPR study reveals some worrying figures for the region’s residents. More than 555,000 homes, many of them multi-family dwellings, are at risk of flooding in the event of flooding on the Seine and Marne rivers. This number represents a considerable population, estimated at over one million people.

River floods are characterized by a gradual rise in water levels. They occur particularly during prolonged periods of heavy rainfall. Since 1910, the Zouave on the Pont de l’Alma has served as a historic alarm bell: when its feet touch the water, a Seine flood begins.

Experts now estimate that such an event has a one-in-a-hundred chance of occurring every year. This may seem a small probability, but it is significant on the scale of a decade or a generation.

“Floods remain unpredictable, but fortunately they are not fast enough to surprise us: the rise in water levels is gradual and would therefore give us time to minimize the risks.”

Water threatens vital infrastructure

In addition to housing, essential infrastructure would be paralyzed. Drinking water production plants, waste treatment centers and data centers are among the facilities at risk. In addition, electrical substations could be affected, depriving entire neighborhoods of power.

A major flood would paralyze much of the equipment needed for our daily comfort. Transport, communications, electricity and gas: all these services could be interrupted for several weeks.

• 555,000 homes at risk of flooding
• Over a million people potentially affected
• Drinking water plants and waste treatment centers under threat
• Data centers and vulnerable substations
• 30 billion euros estimated cost for the Île-de-France region

The historic flood of 1910: a landmark precedent

In January 1910, the Seine reached a record level of 8.62 meters on the scale of the Austerlitz bridge. The Zouave was up to his shoulders in water at the time, an image engraved in the collective memory. It took ten days for the water to rise, and 35 days for it to subside completely.

Fortunately, the human consequences of the Seine flood were not catastrophic. However, the economic consequences were disastrous. Businesses ground to a halt, transport came to a standstill and electricity and gas supplies were cut off for weeks on end.

Today, a similar event would cost the Île-de-France region around 30 billion euros. This considerable sum takes into account material damage, economic losses and reconstruction costs. Consequently, prevention remains a priority for the authorities.

More recent floods: 1982, 2016 and 2018

Since 1910, other episodes have reminded us of the threat posed by the river. Floods occurred in 1982 and 2016, with 6.10 meters of water measured. 2018 saw a further episode, once again alerting the people of Paris.

These recent events have shown that flooding of the Seine remains a reality. They provided an opportunity to test warning systems and evacuation plans. Above all, they served as a reminder of the need to prepare residents to protect themselves.

The most vulnerable districts and municipalities in 2026

The IPR study precisely identifies the areas at risk in the event of a further rise in water levels. In terms of the number of inhabitants at risk, the 15th arrondissement would be the hardest hit. The Beaugrenelle area alone is home to 70,000 people living along the Seine.

In the inner suburbs, a number of municipalities appear particularly vulnerable. Proportional to their population, Alfortville, Asnières-sur-Seine, Gennevilliers, Colombes and Créteil are likely to be the hardest hit. These towns combine high urban density with immediate proximity to the river or the Marne.

Residents of these areas need to be vigilant during periods of heavy rainfall. Knowing how to evacuate and preparing an emergency kit are useful reflexes. However, the gradual rise in water levels means there’s still time to take action and secure essential assets.

Faced with this identified risk, the authorities in the Paris region are pursuing their prevention efforts. Precise knowledge of the areas at risk means that urban planning can be adapted and protection reinforced. Every resident can also contribute by learning how to behave in the event of flooding on the Seine.

• Seine flooding