Redesigning the approach to Miramas to protect against heat islands

Protecting against heat islands

Like every city worldwide, Miramas, a small town in the Bouches-du-Rhône department (France), is experiencing more frequent and more intense summer heatwaves, which are taking their toll on the natural ecosystem and local residents.

The "urban heat island" refers to a phenomenon whereby local urban temperatures are higher than in surrounding rural areas. Caused in part by human activities, the phenomenon is set to grow in all towns and cities as a direct impact of global heating and rising population levels.

In the summer of 2018, under contract from the Ville de Miramas local authority, SUEZ Consulting and its partners began work to transform Boulevard Théodore Aubanel, on the outskirts of the town.

The new linear green space had a number of objectives:

To link Péronne de Miramas urban development zone (ZAC) to the town centre with a high-quality, fun space
To reduce soil waterproofing
To protect existing trees and boost urban biodiversity
To use resources sustainably

Environmental issues as a key concern

Inaugurated in July 2019, the boulevard transformation project adopted measures to meet urban issues:

Climate change resilience and adaptation

Creation of an urban park using existing vegetation
Choice of draining coatings with higher albedo than traditional surfaces to reduce overheating
Disconnection from rainwater system and water infiltration
Reduction in light pollution
Protection of existing vegetation, particularly pine trees

Water cycle

De-waterproofing the road surface using a stabilised sand coating
Turning the former road into a green space
Creating longitudinal parking spaces in a combination of earth and stone covered with crushed grave
Creating ponds designed for direct infiltration into the water table

Circular economy and energy savings

Walls and street furniture made from raw earth and pebbles from the construction site
Lighter road surface (than traditional methods) to reduce the quantity of artificial light required to achieve the requisite level of lighting for urban streets

over

30,000

plants and trees planted

Electrical energy savings of 30%

Well-being, appeal and social cohesion among local residents

Rethinking urban landscapes to meet residents' new usage requirements:

A new public meeting space to enhance social cohesion
Soft mobility solutions encouraged through an 800m-long pedestrian and cycle path, protected from road traffic
A shady pedestrian promenade
An educational garden
An event space for local clubs

The results

Once the development work was complete, our engineers conducted heat assessments to determine the project's impact on urban cooling. The infrared images show surface temperatures, which give two pieces of information that are interpreted differently according to when the images are taken:

At night, they identify materials with high thermal inertia, which accentuate the heat island effect
In the daytime, they show how materials are heated by sunlight, causing thermal discomfort for users

Thermography reveals a difference in surface temperature of 10°C under equal conditions, in sunshine, between tarmac and the stabilised surface used on the new Promenade Aubanel. The difference is caused in part by:

The lighter surface reflecting energy rather than storing it. Albedo of 0.098 previously, compared with 0.369 now
De-waterproofing the promenade and fountains causes evapotranspiration of plants, cooling the surrounding air
Shade provided by century-old trees and pergolas