Lyon, France
#00197
Case study of
#00009 Catchment-wide rain gardens and sustainable drainage to cut runoff at source
Implementer
Metropole de Lyon, ville permeable program
Timeline
Since Jan 1, 2020
Location
Description
Since 2020 the Metropole de Lyon has run a "ville permeable" (permeable city) program, systematically disconnecting surfaces from the sewer network or depaving them so rain infiltrates where it falls. By 2025, 255 hectares had been disconnected or depaved against a target of 400 hectares by 2030. The 2025–27 phase is structured as a contract of 190 enumerated actions worth 286 million EUR, of which 53.9 million EUR comes from the Agence de l'Eau Rhône Méditerranée Corse. The cost recorded is the 2025–27 contract only, not cumulative spending since 2020. Schoolyard conversions lag significantly: roughly 10 completed against approximately 50 promised, illustrating that headline hectare targets can be on track while specific sub-categories fall behind.
Metrics
3Funding
Lessons learned
- Agence de l'eau co-financing is the decisive enabler: secure the basin agency contract before scaling — it is what converts a policy ambition into a funded pipeline of discrete actions.
- Underground network costs (locating, cutting, and rerouting buried pipes) dominate per-site budgets; the visible surface depaving is the cheap part, so survey buried infrastructure early in site selection.
- Structure the program as a multi-year contract of enumerated actions (e.g. 190 actions, 2025–27) to create an auditable pipeline rather than a vague target.
- Track and publish per-category progress (streets, plazas, schoolyards separately): aggregate hectares can appear on track while politically visible sub-categories lag badly.
Documented Jul 24, 2026