Ille-et-Vilaine

Recorded Natural Hazards (Géorisques)

It has 332 municipalities and 1,120,666 inhabitants. Under the seismic zoning in force since 2011, its highest seismicity is low (zone 2 of 5). A natural disaster has been declared 1,809 times since 1982 (one declaration per municipality and decree), mostly for floods (1,079) and ground movements (346). The most recent was signed on 18 January 2026. 212 municipalities have a high radon potential (category 3), home to 63% of inhabitants. 114 municipalities are covered by an approved natural hazard prevention plan.

Seismicity Zones

Number of municipalities in each zone of the regulatory seismic zoning (from 1, very low, to 5, high).

Natural Disasters Declared Since 1982

Declarations per five-year period.

Most Widespread Events

• 1999Ground Movements · 25 December 1999332 municipalities
• 1999Floods and Mudflows · 25 December 1999332 municipalities
• 1987Storms · 15 October 1987332 municipalities
• 1995Floods and Mudflows · 17 January 199597 municipalities
• 2025Floods and Mudflows · 23 January 202570 municipalities
• 2001Floods and Mudflows · 5 January 200128 municipalities

Most Frequently Affected Municipalities

• 16Guichen
• 16Guipry-Messac
• 15Redon
• 14Goven
• 14Montfort-sur-Meu
• 14Pacé
• 14Rennes
• 13Bréal-sous-Montfort

Hazards Listed by Municipality

Number of municipalities exposed to each natural hazard according to the departmental major risks file.

Hazards at a specific address on Géorisques