Flooding in Western France: Rennes Grapples with Worst Levels in 40 Years
Rennes is facing its worst flooding in 40 years following days of heavy rainfall and the impact of Storm Herminia, which began battering Normandy and Brittany on January 25, 2025. The Vilaine River has reached or surpassed historic levels, with some areas experiencing water levels exceeding those recorded in 2001.
The mayor of Rennes described the current flooding as the worst the city has seen in four decades, with nearly 400 residents evacuated. Residents described waking up to water levels reaching their hips, forcing some to escape through windows and seek refuge in local businesses to charge their phones.
The situation is further complicated by the forecast of Storm Ivo, expected to bring gale-force winds of 80-100 km/h (50-62 mph) and moderate rainfall to Brittany, potentially exacerbating the ongoing flooding. At least two people have died in France as a result of Storm Herminia.
Water levels in the Vilaine River basin are being closely monitored by Eaux et Vilaine. In Guichen, the water level currently matches that of January 2001, while in Guipry-Messac, the 2001 record has been surpassed by 20 cm (7.9 inches). While flooding is expected to stabilize in some areas on January 28, water levels in Redon are still rising and could reach a historic high of 5.35 m (17.6 feet), previously recorded in 2001.
Impact on the Real Estate Market
The recent floods are beginning to impact the real estate market in Rennes. Real estate agents report that potential buyers are increasingly asking if properties are located in flood zones, a question that has “made a comeback” following the January 2025 floods. The increased awareness of flood risk is leading some buyers to reconsider purchases or to negotiate lower prices.
Approximately 30,000 residents of Rennes already live in areas designated as flood zones, a number that is expected to slightly increase as the state revises risk assessments for the Vilaine basin. A new risk map, published recently, identifies additional streets and sectors in Rennes now classified as flood-prone areas. However, many residents reportedly remain unaware of these changes and the associated urban planning restrictions.
New Restrictions and “Bands of Caution”
The implementation of “bands of caution” – areas identified as being at risk if existing flood protections fail – is introducing significant restrictions on construction. These bands were established following the lessons learned from the 2010 “Xynthia” storm, which caused widespread damage and loss of life when storm surges overwhelmed coastal defenses, including the tragic events in La Faute-sur-Mer, where 29 people died.
Within these bands, obtaining building permits is becoming increasingly difficult. Several sales have already failed due to these restrictions. The most significant band of caution in Rennes, approximately 300 meters wide, is located south of the Quai de la Prévalaye. Future construction within these zones will likely be limited to projects undertaken as part of urban renewal initiatives designed to improve resilience to flooding.
While existing buildings within the bands of caution are not expected to be required to undergo immediate renovations, owners of vulnerable properties, such as single-story homes below the reference level, may be asked to commission a vulnerability assessment from a qualified engineering firm.
The new regulations are expected to significantly impact property values in affected areas, according to local real estate professionals.
