Green roof – the solution to urban flooding

In recent times, Europe has been struck by large-scale floods, causing significant damage to both homes and urban infrastructure. The intensification of extreme weather phenomena has brought to light the vulnerability of cities in the face of these challenges, especially due to the uncontrolled expansion of impermeable surfaces and the absence of sustainable storm-water management strategies. As a consequence, floods have become increasingly frequent, generating substantial costs for the required repairs.

Even the Netherlands, renowned for its innovative water-management solutions, has faced major difficulties. Cities such as Rotterdam and Amsterdam were overwhelmed by enormous amounts of precipitation, exceeding the capacity of drainage systems and causing significant disruptions. Additionally, Budapest, the capital of Hungary, was severely affected by torrential rains, which blocked transport and turned entire districts into flooded zones.

In Germany, the city of Cologne was severely impacted, with streets turning into rivers and homes invaded by water, affecting the lives of thousands of people.

These extreme events have once again underscored how exposed urban infrastructure is to climate change, especially in the context of heavy rainfall, which is becoming increasingly frequent.

Romania too has not been spared these challenges. In cities such as Bucharest, Galați, Cluj-Napoca and Iași, the torrential rains of 2024 caused severe floods, paralyzing traffic, affecting the local economy and putting pressure on the transport and utilities network.

Brașov was among the cities heavily affected by the torrential rains in the summer of 2023, together with Bucharest and Galați. In particular, the Bartolomeu and Tractorul districts were hit hard, where sewer networks could not cope with the large volume of water, turning streets into actual lakes and flooding homes and basements.

These extreme phenomena caused considerable material damage, affecting both infrastructure and the well-being of residents, who faced major difficulties in their daily lives.

In the face of these challenges, construction specialists, real-estate developers and local authorities are under increasing pressure to implement sustainable solutions for storm-water management.

An efficient and eco-friendly solution is green roofs, which not only reduce the risk of floods but also bring numerous benefits to the urban environment and infrastructure.

Why is the adoption of effective measures against urban floods urgent?

According to a report by the World Bank, floods account for 40% of natural disasters in Europe and generate estimated annual damage of €30 billion. Extreme weather phenomena are becoming more frequent, and Romania is no exception. In the summer of 2024, Bucharest faced severe floods, especially in areas where drainage infrastructure is overwhelmed and unable to cope with large volumes of water in a short time. The National Administration “Romanian Waters” confirmed that the sewer networks in major cities no longer meet current requirements, being designed for more stable climatic conditions.

In this context, green roofs can become an effective solution to reduce pressure on these systems and to prevent excessive accumulation of water in urban areas.

How do green roofs contribute to reducing the risk of flooding?

Thanks to their layered structure, green roofs act as a natural buffer, absorbing and retaining rainwater before it reaches the sewer system. Vegetation layers and integrated drainage systems slow down water run-off, thus reducing the risk of floods.

A study by the University of Toronto found that green roofs can retain up to 70% of precipitation, significantly reducing the impact of torrential rains on urban infrastructure. In addition, vegetation promotes evaporation of water, thereby contributing to a more balanced natural water cycle.

Cities such as Berlin have invested heavily in green infrastructures, including green roofs, after the floods of 2021 revealed deficiencies in the drainage system. By 2024, these measures had significantly reduced the effects of heavy rains, demonstrating the effectiveness of sustainable infrastructure.

Examples of best practices: Green roofs as a solution for flood-prone cities

A compelling example of the effectiveness of green roofs in preventing floods comes from Copenhagen. Following the torrential rains of 2011, which caused more than US $1 billion in damages, the municipality adopted an urban strategy focused on sustainable infrastructure.

The integration of green roofs and other natural drainage solutions significantly helped reduce the volume of water directed to the sewer system, thus lowering the risk of floods in critical zones.

In Germany, Hamburg followed a similar approach, implementing green roofs on both public buildings and residential complexes. The results were remarkable: in areas where these measures were applied, the probability of floods dropped by 25% over the past three years, demonstrating the efficiency of green solutions in storm-water management.

Sustainable initiatives in Romania

In Romania as well, cities are beginning to adopt concrete measures to limit the effects of urban floods. For example, Brașov has started projects to improve the drainage system in the Bartolomeu district, combining infrastructure modernisation with the development of green spaces capable of absorbing rainwater. In the long term, the municipality is considering the possibility of introducing green roofs on public and commercial buildings, thereby reducing pressure on sewer networks during heavy rainfall.

Another example is Cluj-Napoca, where local authorities, faced with floods in recent years, have launched an integrated climate-adaptation strategy. This includes the creation of urban parks capable of retaining rainwater, the use of permeable materials for street paving and the promotion of green roofs for new real-estate developments. In parallel, Cluj is investing in the modernisation of the sewer network and in the implementation of an efficient storm-water collection and management system.

These examples show that cities in Romania are beginning to adopt sustainable solutions to combat the effects of extreme weather phenomena. Green roofs are becoming a key pillar in flood-risk-reduction strategies, offering benefits for both infrastructure and the urban environment.

Green roofs: A solution with multiple advantages for sustainable cities

Green roofs offer benefits that far exceed simple storm-water management. They contribute significantly to building energy efficiency, improve urban environmental quality and support sustainable development — all essential for architects, real-estate developers and local authorities.

Improved energy performance

Thanks to their insulating properties, green roofs help reduce energy consumption. In winter, they help retain heat inside, diminishing heat losses and lowering heating costs by up to 75%. In summer, they prevent the overheating of buildings, significantly reducing the need for air-conditioning.

Cleaner air in the urban environment

The vegetative layer of green roofs captures fine particles and atmospheric pollutants, contributing to improved air quality, especially in densely populated cities where pollution reaches high levels.

Tackling the urban heat-island effect

Concrete and asphalt surfaces absorb and retain heat, making cities substantially warmer than surrounding areas. Green roofs counteract this phenomenon, reducing local temperatures and providing a more pleasant urban climate. By integrating these solutions, cities can become more sustainable, more energy-efficient and more environment-friendly, thus improving residents’ quality of life.

Implementing green roofs in Romania: Obstacles and solutions

Although the benefits of green roofs are well known, their implementation in Romania faces several challenges. Among the main hurdles are the upfront costs, which may seem high at first glance. However, it is essential to emphasize that this investment pays off over the long term through substantial savings in energy and maintenance.

Another significant benefit is that the lifespan of a traditional roof can be extended by up to 40 years thanks to the protection provided by vegetation against external factors. In countries such as Germany and the Netherlands, authorities support these initiatives through subsidies and tax incentives — an approach that could accelerate the deployment of green infrastructure in Romania too.

We act now, not just react!

Instead of intervening only after disasters, we can adopt solutions that prevent problems before they occur. Close collaboration between architects, developers and authorities can transform Romanian cities into examples of urban sustainability.

Green roofs are more than an innovation – they represent a commitment to the future, a solution that protects today and ensures a safer, healthier environment for future generations.

Every step counts. Every green roof brings change!