Meanders of the Sèvre, gardens of the Brèche, Port Boinot… Ancient or recent, several islands of coolness lower the temperature in Niort, just as a heat wave is approaching. Vegetated places, called to multiply in the years to come.
Be careful, the thermometers will panic. Almost everywhere in Poitou-Charentes, temperatures will exceed 30°C this Friday July 31st. It should therefore make 34 in Poitiers and 37 in Angoulême. 35 degrees are expected in Niort. Temperatures that will not occur anywhere in the city.
In the Jardins de la Brèche, for example, the mercury could be at least 4 degrees lower than in other areas of the city. That’s the cooling island effect, a buzzword used by urban planners among ecologists and those who fear the sharp heat surges expected to sweep urban environments over the next few decades.
The secret of an island of freshness is to give back some space to nature in our paved environments. A principle which translates, at the Brèche, into trees, large grassy areas and limitation of the mineral surface.
“The grass helps create evaporation of water from the soil“, explains Gwenaëlle Dubée, director general of technical services of the city of Niort. Indeed, the transpiration of the plant consumes the heat of the surrounding air to evaporate the water it draws from the ground. “With 1 liter of water evaporating, 1,000 cubic meters of air are reduced by 2 degrees“, continues Gwenaëlle Dubée.
Tar holds heat, weed sends it back
At La Brèche, the current 4-hectare park replaced an asphalt car park in 2013 (it is now buried underneath) with 1,000 spaces. A real breath of fresh air: “We gained between 4 and 8 degrees of cooling, especially in the center of the gardens, compared to the car park“, specifies the director general of technical services.
But the evaporation of the water does not fight against the sun’s rays on its own within an island of freshness. Tar has a very low albedo, that is, it reflects the sun’s rays very poorly. Therefore, it absorbs heat and warms up its surroundings. The solution: replace the tar with other coatings.
At La Brèche, these coverings are naturally grass, and for the paths, a light mineral material which reflects much of the light emitted by the sun. To this must be added some 300 trees, which provide saving shade when the rays hit hard. Results: “There is really freshness, especially compared to the alley in front of the cinema. While being in a sunny space“says an ordinary gardener.
“Even the otters and herons are back“
Initiated more than fifteen years ago, the Brèche plant project has had numerous successes. In the meanders of the Sèvre, the industrial desert of Port Boinot has also begun its green transformation. Port Boinotthere are 7,000 square meters of lawn and 140 trees planted (a dozen are missing to be fixed).
An important project for the mayor of the city Jérôme Baloge, which still resembles a “smoky and polluted industrial site, with few sheds, 2m high concrete block walls set on paved banks“. And after the revegetation of the banks, he rejoices in the “return of the ducks. Even the otters and herons are back.“
And compared to the Berge, Port Boinot has two further advantages. Already, “nature is in direct contact with the ground, and does not rest on a superstructure, indicates the mayor of Niort. This allows rainwater to seep into the ground instead of going down the drain.“Another strong point: Port Boinot is surrounded by water. Two arms of the Sèvre, which are further sources of freshness.
Jérôme Baloge promises that Niort will not stop there, and says he wants “reflecting on the islands of freshness in urban planning and in all city projects, large and small as well“. Before announcing that he “there will be green at the station, there will be greenery in Denfert-Rochereau, there will be green in Martin-Bastardand we will put trees on the avenues where possible“.
Futuristic visions of completely green cities are not for tomorrow. But while ecology is becoming a key issue in French society, natural islands of coolness are becoming commonplace in urban planning projects.
