Swimming in the Rhône or urban forests, how Lyon adapts to the heat

One Tuesday in June, on the eve of summer, Odile Barbier, a 66-year-old retiree, stopped at the "freshness" stand run by the local Energy and Climate Agency (Alec) on a market in Lyon. She talks about her fight with the co-ownership to do insulation work.

“I will never put the air conditioning in my house, I don’t want to make things worse,” she assures.

Cities are particularly sensitive to heat, "not only because of climate change, but also because of the problem of urban overheating", recalls Florent Renard, teacher-researcher at Jean-Moulin Lyon 3 University: excessive mineralization , solar radiation trapped in the streets and other effects of human activities (industries, transport, etc.) contribute to this.

The heatwave of 2023 pushed the city of Lyon to add 14 measures to its “Freshness Plan”, including free museums, cinema tickets offered to people of modest means, or supervised swimming in the Rhône.

In the event of a red alert, the environmentalist municipality will test a new measure: allowing people to sleep under the stars in a park.

“Our objective is to develop a range of services and leisure activities that allow people to leave their homes to find respite,” summarizes Sylvain Godinot, deputy for ecological transition.

These measures, necessary when "the speed of home renovation is much slower than climate change", are accompanied by longer-term investments, such as installation in municipal establishments (schools, nurseries, etc.). ) solar protection or air fans, or shading of parks.

Greening is one of the main solutions in creating islands of freshness, with the de-waterproofing of soils, “stripped” of their concrete.

Revegetation

The long Garibaldi street which crosses the east of the city, the first redevelopments of which date back to 2010, has been equipped with sensors. Between a space with “a plane tree every 14 meters” and “bubbles of vegetation”, the difference is more than 4°C, up to 7,6°C in the event of a heatwave, reports Pierre Athanaze, vice-president at the Metropolis.

Lyon was a pioneer in terms of a "permeable city", a concept which aims to "reconnect rainwater to the water table, no longer send it directly to the wastewater network, and use it to green the city", explains Florent Renard, teacher-researcher at Jean-Moulin Lyon 3 University.

Like the creation of the Urban Hydrology Field Observatory (Othu) at the end of the 1990s.

“During the last three mandates, we planted 1.200 to 2.000 trees per year. This winter, we planted 52.000,” underlines Pierre Athanaze. A rhythm which is accompanied by work to allow the infiltration of water and the recovery of rainwater.

One of the objectives is the creation, when possible, of “urban forests”, “at least two hectares”.

To be able to reach private spaces, the metropolis subsidizes plantations between 50 and 65% in collective housing, and will distribute 2.000 trees free of charge to the inhabitants of Greater Lyon.

The metropolis has voted a budget of 50 million euros for its Nature Plan, established in 2021.

Cold networks

Lyon can also count on two urban cold networks. One in the La Part Dieu district, inaugurated in September 2022, "which refreshes a little more than a million square meters, notably offices, shopping centers, and one in Gerland, in the basement of the skate park, which cools 300.000 square meters", explains Philippe Guelpa Bonaro, vice-president of the metropolis in charge of Climate and Energy. They deliver chilled water to buildings to cool them.

The metropolis is also betting on renovation with bio-sourced materials and a “bioclimatic PLUH” (Local Urban Planning and Housing Plan) with an increasing “open land coefficient” and “a required orientation of constructions to allow natural ventilation.

In this ongoing quest for adaptation solutions, the metropolis is preparing to launch a citizens' convention.

“The urban fabric being extremely heterogeneous, each street has its solution. That’s the problem,” recalls Florent Renard.