Rethink Cities for Extreme Heat: Capture Water, Grow Green, Says Architect

Cities need a fundamental shift in how they manage water and integrate nature to combat rising extreme heat, according to landscape architect Bas Smets. He points to striking temperature differences, such as a recent 47-degree Celsius reading in Brussels while a nearby forest remained a mild 24.5 degrees, as evidence of the urgent need for change.

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We must fundamentally rethink the water cycle in our cities. Today, we have paved over most surfaces, causing water to be collected, drained away, and sent into the sewer system, thus removing it from the system.

Smets, known for his work on projects like Tour & Taxis Park in Brussels and Nieuw Zuid in Antwerp, argues that current urban design prioritizes rapid water drainage, leading to downstream flooding and reduced groundwater. "We must fundamentally rethink the water cycle in our cities," he stated. "Today, we have paved over most surfaces, causing water to be collected, drained away, and sent into the sewer system, thus removing it from the system."

He advocates for capturing rainwater where it falls to support plant and tree life, which actively cools urban environments through evapotranspiration. "Trees can absorb water and release it back into the atmosphere through their leaves, providing cooling," Smets explained. This requires a "mindset shift" to see urban spaces not as obstacles to nature, but as opportunities for it.

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Trees can absorb water and release it back into the atmosphere through their leaves, providing cooling. That is called evapotranspiration.

Smets calls for cities to be designed as basins that collect water, with systems to store and reuse rainwater beneath pavements and in parks. He cites Paris's recent efforts under Mayor Hidalgo to reduce impermeable surfaces as a positive example of this approach. The goal is to create more space for root systems and allow nature to actively cool the city.

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We must see the city as an opportunity for nature. This mindset must change, and then we will look very concretely at: okay, what is now under my pavement? Where do I find space for these roots?