A Silent Threat Underneath Lyon
In Lyon, France’s third-largest urban city with 1.4 million residents, are suffering from prolonged heatwaves and dry spells drying out clay-rich soils, and causing them to contract. When heavy rain falls, these dehydrated soils expand rapidly. This process, known as clay shrinkage and swelling, destabilises foundations, buckles roads, damages underground utilities, and cracks house walls:
- 26% of homes in Metropolitan Lyon are located in areas with high clay content
- Between 2009 and 2020, 47% of municipalities in the region filed natural disaster claims due to ground movement.
- The severe drought of 2022 alone cost the French national insurance framework an estimated €2.4 billion to €2.9 billion.
To make matters worse, homeowners face a substantial insurance coverage gap. France’s Catastrophes Naturelles (Cat Nat) insurance scheme requires official municipal disaster declarations. As a result, many property owners are left without financial protection when structural damage occurs.
The PIISA Project & Open-Data Pioneers
The PIISA Mission Project, an EU Horizon Europe-funded initiative, alongside data scientists from AMIGO Srl and local regional partners, recognised that technical climate models were not reaching the people who needed them most.
The project team stepped in to empower citizens by translating complex geological and climate data into clear, accessible language, bridging the gap between technical expertise and individual local action.
To tackle soil instability and insurance ambiguity, the project created the Clay Shrink Swell Building Damage Assessor, an intuitive digital dashboard designed specifically for homeowners, int includes:
- 3-Minute risk assessment
- Financial risk calculations
- Preventive guidance
The pilot combined digital outreach with hands-on citizen workshops and presence at local gatherings, such as the Ethical Finance Forum in May 2025. Following its success in Lyon, this open-data methodology has been expanded nationwide across France and provides a scalable model for other European regions facing similar climate hazards.