How smart water storage on rooftop gardens is becoming increasingly important

You probably recognise it.

It starts with a few dark clouds and five minutes later the streets are flooded. Drains overflow, cars crawl along, and the road slowly turns into a small river with nowhere for the rainwater to go.

This is happening more and more often. Our cities are increasingly facing extreme rainfall. However, the way we have designed our urban environments simply isn’t built to cope with it. Large amounts of rainwater flow straight into the sewer system, which often cannot handle these intense peaks. Meanwhile, something interesting is happening in a place we normally barely notice: on the roof.

The roof is suddenly more important than ever

In the past, a roof was just… a roof. It kept the rain out, and that was about it. Today, roofs are becoming greener and smarter. Especially in cities, where every square metre counts, roofs offer enormous opportunities. Green roofs and rooftop gardens contribute to cooling, biodiversity, and a greener living environment. But during extreme rainfall, the soil or substrate layer quickly becomes saturated. And then the water still has to go somewhere. That is why modern rooftop gardens are no longer just about greenery – they are increasingly about smart water management. After all, why should we let rainwater drain away immediately when we could store it temporarily?

The smart solution lies beneath the greenery

To truly capture rainwater effectively, more is needed than just planting. Water storage beneath the rooftop garden plays a crucial role.

With AquaRaft from GreenMax, rainwater is temporarily stored beneath the greenery, preventing it from flowing straight into the sewer system during peak rainfall. Once the bulk of the water has been processed, it is released in a controlled manner.

AquaRaft uses lightweight, largely hollow water storage crates that can hold large volumes of water without placing unnecessary weight on the roof. This not only helps prevent flooding, but also ensures that rainwater remains available to the vegetation on the roof for longer. In addition, AquaRaft is used beneath sports fields, where it captures rainwater without compromising load-bearing capacity or playing quality.

What makes AquaRaft smart:

• Temporary storage of rainwater
• Reduced load on the sewer system
• Lightweight system for rooftop gardens
• High water storage capacity
• More space for greenery and biodiversity
• Simple and quick to install
• Service life of at least 50 years

Rainwater is becoming increasingly valuable

Perhaps this is the biggest change in recent years: rainwater is no longer seen as something that should disappear as quickly as possible. We are not only experiencing more extreme rainfall, but also longer dry periods. That is exactly why storing water intelligently is becoming more important. As a result, the focus is shifting upwards. Roofs are becoming not only greener, but also smarter. By temporarily storing rainwater, they help reduce flooding, heat stress, and drought in urban areas.

So next time there’s a sudden downpour, look up. That roof above your head might be doing far more than you think.

Advice on water management

Integrated solutions for green, grey and blue infrastructure form the foundation of our approach at GreenMax. From growing spaces and urban trees to water storage on roofs and beneath sports fields. With years of (inter)national practical experience, we are happy to help design smart solutions for capturing, storing and draining water, where greenery and water reinforce each other. Together, we create practical, climate-resilient solutions that truly work. Book a no-obligation consultation with one of our experts!

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Summary

Extreme rainfall is increasingly causing flooding in urban areas, as sewer systems cannot cope with peak loads. Rooftop gardens and green roofs offer an effective solution by temporarily capturing rainwater and releasing it slowly. With smart water storage systems such as AquaRaft from GreenMax, water is stored beneath the greenery, reducing pressure on the sewer system while keeping water available for plants for longer. These lightweight and durable systems combine water management with greening and contribute to climate-resilient cities. By using rainwater intelligently instead of draining it away immediately, roofs are playing an increasingly important role in reducing flooding, heat stress and drought.