01.02.2026

Green Infrastructure for Heavy Rainfall – A Comparison of Solutions

Building design

Green urban landscape shows solutions for urban water management and climate adaptation.

Green Infrastructure for Heavy Rainfall? What was once considered just “greenery” along the roadside is now becoming a high-performance system in urban water management. Climate change is making heavy rainfall the new normal—and the question of which solutions really work has become the most pressing issue for planners, landscape architects, and local governments. Which systems protect the city, and which are merely a placebo? A comparison that dares to put them to the test.

Definition and Significance of Green Infrastructure in the Context of Heavy Rainfall Events
Analysis of traditional versus innovative solutions: basins, retention roofs, sponge cities, infiltration areas, and more
Detailed examination of the mechanisms, advantages, and disadvantages of various systems
Evaluation of effectiveness based on real-world examples from German-speaking countries
Legal, planning, and societal framework conditions
Synergies between green infrastructure, biodiversity, and urban quality of life
Risks, challenges, and limitations of implementation
Outlook: Urban development, climate adaptation, and the role of interdisciplinary collaboration
Conclusion: Which solution really stands out, and what remains to be done?

Green Infrastructure: New Heroes in the Fight Against Heavy Rainfall

Anyone strolling through German cities today will encounter them everywhere—the new heroes of water management. Green infrastructure may sound like parks and trees, but at its core, it is much more: it refers to all nature-based, vegetation-based systems that absorb, store, evaporate, or allow rainwater to infiltrate. In the age of climate change, they are emerging as key technologies, because heavy rainfall is no longer a rare extreme event but rather a meteorological reality of everyday life. The consequences: flooded basements, waterlogged streets, and destroyed infrastructure. Traditional sewer systems quickly reach their breaking point. The urban planning response: the sponge principle.

The “sponge city” concept—as simple as it is ingenious: Cities must not only drain water but, above all, be able to absorb and retain it. Rainwater basins, retention roofs, green spaces, permeable pavements, and urban wetlands play the leading roles here. They form a decentralized network that buffers rainfall and slowly releases it again. The key: these systems work with, not against, nature. They improve the microclimate, promote biodiversity, and enhance the quality of life in the neighborhood.

But green infrastructure is not a panacea. Its effectiveness depends on location, planning, and maintenance, as well as on legal requirements and financial resources. While many municipalities are focusing on trendy pilot projects, widespread implementation often remains piecemeal. Anyone who wants to know which solutions really work has to dig deeper—both literally and figuratively.

Planners today face the challenge of finding the right systems for each urban structure. While space is at a premium in urban centers, suburbs and new development areas offer more leeway for large-scale measures. What matters here is not only technical performance but also public acceptance and maintenance by residents. Added to this are questions of financing, long-term maintenance, and integration into existing infrastructure networks.

The good news: green infrastructure isn’t just a pipe dream. It’s already being used successfully—from the tree-lined boulevard in Vienna to the multifunctional retention park in Hamburg. But which systems are truly resilient, and which are more marketing hype than substance? It’s time for a critical, practical comparison.

Comparing Traditional and Innovative Solutions: Basins, Roofs, Sponges, and More

Let’s start with the classic: the rainwater basin. These slightly sunken green spaces absorb large volumes of water during heavy rainfall, store it temporarily, and then slowly release it into the ground. Their advantage is their simplicity—they require little technology, are cost-effective, and can be integrated almost anywhere. But basins quickly reach their limits: they’re often overwhelmed during extreme events, and they also require space, which is in short supply in city centers.

Retention roofs are the answer to the lack of space in urban areas. They transform roof surfaces into temporary water reservoirs. Special substrates and drainage layers retain the rainwater and release it gradually. This relieves pressure on the sewer system and cools the building. But here, too, the load-bearing capacity of old roofs is limited, installation is complex, and maintenance is demanding. And: The storage capacity is finite—during prolonged rain, the roof quickly turns into a bathtub.

Permeable paving, such as grass pavers or special paving stones, allows rainwater to seep directly into the ground. They are standard in new development areas but rare in historic city centers—retrofitting is too complex, and soil conditions are often too unclear. Furthermore, infiltration is only partially effective in compacted or contaminated soils.

A true game-changer is the “sponge city” principle: here, the entire city is conceived as a water reservoir. Large parks, urban wetlands, planted ditches, and open water bodies form a network that absorbs water, filters it, and slowly releases it again. This system is being successfully implemented, for example, in Copenhagen, where the city center remains dry even after once-in-a-century downpours. But implementation is challenging: it requires space, long-term planning, and a willingness to completely rethink urban design.

Innovative systems such as green facades, tree trenches, and urban rain gardens round out the portfolio. They provide additional evaporation surfaces, cool the surrounding area, and create habitats for insects and birds. But even these solutions aren’t a sure thing: without proper care and irrigation, they risk drying out, and if implemented incorrectly, they can even cause damage. Choosing the right solution is therefore always a matter of local conditions and the willingness to take care and maintenance seriously.

Real-World Examples: What Really Works—and What Are the Limits?

A look at real-world applications shows that there is no one-size-fits-all solution—only tailored strategies. In Hamburg, for example, entire neighborhoods have been redeveloped according to the “sponge city” principle. Retention areas, wide ditches, and green roofs ensure that heavy rainfall is almost completely retained on-site. The result: less flooding, better air quality, and a higher quality of life. But even here there are limits: during exceptionally heavy rainfall, even the most modern systems reach their limits, basements flood, and streets are submerged. The lesson: Green infrastructure can do a lot, but it cannot do everything.

In Vienna, the focus is on a combination of retention roofs, rainwater gardens, and open waterways. New neighborhoods like Seestadt Aspern in particular demonstrate just how multifunctional green infrastructure can be: it serves as a playground, a recreational space, and a water reservoir all at once. But here, too, maintenance is crucial—neglected areas quickly deteriorate, become breeding grounds for mosquitoes, or lose their function. Regular maintenance, monitoring, and civic engagement are therefore essential.

Zurich is taking a different approach: there, the focus is on digital control. Sensors in basins and reservoirs monitor water levels in real time, and automatic valves control drainage. The result is a high degree of reliability—but also significant technical complexity. The costs are considerable, and maintenance is complex. Nevertheless, this example shows that the combination of green and gray infrastructure—that is, natural and technical elements—offers the highest level of resilience.

Smaller cities are also getting involved: In Freiburg, for example, open ditches, troughs, and infiltration areas are being integrated as standard features in new development areas. Acceptance among residents is high; the areas are used and valued as green spaces. The challenge: Retrofitting existing areas is difficult; space is limited, and ownership structures are complex. This calls for innovative, flexible solutions—and patience.

What all these examples have in common: Green infrastructure works best as a network, not as an isolated measure. True resilience is achieved only when depressions, rooftops, infiltration areas, and parks are intelligently interconnected. Crucial to this is the cooperation of all stakeholders—from the administration and planners to the general public. Without communication and maintenance, even the most beautiful solution remains a patchwork effort.

Legal, Planning, and Social Framework Conditions

Green infrastructure always sounds like a free play of forces, but in reality it is a complex web of regulations, responsibilities, and interests. In Germany, the Water Resources Act governs the infiltration and retention of stormwater—and in many places mandates decentralized stormwater management. But implementation is often a struggle: municipalities, property owners, and utility providers vie over land, costs, and responsibilities. On top of that, funding is usually project-specific; grants are scarce and often tied to strict requirements.

Planners must navigate a jungle of standards, ordinances, and grant programs. DIN 1986-100 governs the design of drainage systems, while DIN 18035 addresses the design of green spaces. However, many requirements are tailored to traditional systems and do not adequately account for innovative solutions. Anyone who wants to experiment needs courage, persuasiveness—and sometimes a lot of patience.

Societal acceptance of green infrastructure is high—as long as it is visible and usable. Parks, rooftop gardens, and green spaces are well-received. Things get more difficult with invisible systems such as soakaways or underground drainage trenches—here, there is often a lack of understanding regarding their benefits and maintenance requirements. Education, public participation, and transparency are therefore key factors for success.

Another issue: maintenance. Green infrastructure is labor-intensive and requires regular monitoring, pruning, and cleaning. Many municipalities underestimate the effort involved—resulting in overgrown facilities, clogged basins, and non-functional systems. Without long-term maintenance plans, there is a risk of losing functionality—and with it, public acceptance.

Last but not least: Climate change is placing greater demands on planning. Precipitation is becoming more intense, and dry spells are lasting longer. Systems must become more flexible, robust, and multifunctional. This calls for new planning approaches, interdisciplinary collaboration, and a willingness to view mistakes as opportunities to learn. Only in this way will green infrastructure remain an effective tool against heavy rainfall in the future.

Added Value, Synergies, and Limitations: What Can Green Infrastructure Really Achieve?

Anyone who views green infrastructure solely as flood protection underestimates its potential. It is a habitat, an air conditioner, a gathering place, and a driver of biodiversity all in one. Trees, bodies of water, and meadows provide cooling on hot days, filter particulate matter, promote biodiversity, and enhance well-being. These effects are especially valuable in densely populated neighborhoods. But the added value doesn’t come on its own—it must be planned, maintained, and communicated.

The synergies between water management, the urban climate, and quality of life are enormous. Retention areas become play areas, depressions turn into flower meadows, and rooftops become social gathering spots. Projects such as the “Blue-Green Streets” in Rotterdam or Berlin’s “Rainwater Agencies” demonstrate how technical flood protection measures can give rise to vibrant urban spaces. The prerequisite: interdisciplinary collaboration and a willingness to transcend traditional planning boundaries.

But there are also limitations. Not every city can become a “sponge city,” and not every neighborhood has room for depressions, ponds, and parks. Building codes, property ownership structures, and land-use claims restrict the scope for action. And: These systems are not a silver bullet against extreme events. In the event of a once-in-a-century downpour, often only the traditional sewer system can help—or avoiding sensitive land uses in flood-prone areas.

Another risk: the commercialization of green infrastructure. If green roofs become mandatory but maintenance and oversight are lacking, we risk superficial solutions—green facades that wither after a few years, and basins that degenerate into garbage dumps. This requires expertise, oversight, and commitment—from planners, municipalities, and users alike.

And finally: Social acceptance determines success or failure. Those who involve citizens and users and take their wishes and fears seriously foster a sense of identification and responsibility. Green infrastructure then becomes more than just technology—it becomes part of urban life, a symbol of sustainable urban development.

Conclusion: Green Infrastructure for Heavy Rainfall—What Remains, What’s Next?

Green infrastructure is not a panacea, but an indispensable building block of the climate-resilient city. Its strengths lie in its decentralized nature, versatility, and the added value it provides for people and nature. The best systems operate as a network, combining basins, roofs, infiltration, and technology into a robust, adaptable overall strategy. The quality of planning, maintenance, and the willingness to learn from mistakes are crucial.

The challenges remain enormous: lack of space, legal hurdles, financing issues, and the balancing act between technology and nature pose challenges for planners, municipalities, and users alike. Yet practical experience shows that where green infrastructure is taken seriously, maintained, and further developed, it not only protects against heavy rainfall but also creates livable, attractive urban spaces.

The future lies in the combination of innovation and tradition, of technical precision and natural diversity. The “sponge city” is not a distant dream, but an ambitious goal—achievable with courage, expertise, and the will to collaborate. Those who set the right course today can shape the city of tomorrow to be not only flood-resistant but also a great place to live. And that’s more than just a trend—it’s the new benchmark for sustainable urban development.

20.01.2025

Design

Sculpture of the month: Stone postcard from Solingen

Building design

Bush knife: The Solingen cutting tool turned stone on the right by the hedge. On the left, an unnamed steel sculpture by Thomas Röthel

Steel products from Solingen, especially knives, are known all over the world. Even in the South American jungle, Bud Spencer warned his partner Terence Hill of a “postcard from Solingen” in his back – i.e. the switchblade in the hand of the sneaking attacker – in the 1973 cinema classic “Two Heavenly Dogs on the Road to Hell”. For the tenth anniversary […]

The Solingen trade fair focuses on the products of local industry, in the classic city of blades, of course, especially the well-known steel products. Directly opposite the venue of this largest trade fair in the Bergisches Land region – the local ice rink – is the premises of Marmor Pauly, which has been working in natural stone since 1871. “A knife doesn’t always have to be made of steel,” thought owner Armin B. Pauly, architect and graduate civil engineer.

And it doesn’t have to be handy either: together with the self-employed stone sculptor Hartmut Hegener, he created a butter knife sculpture on a scale of 10:1 to place in front of the entrance to the trade fair and point out that, in addition to the proud steel tradition, there are also many years of stone masonry activity. The knife measures 2.30 meters with a handle made of polished Anröchter Grünstein, a calcareous sandstone from the Soest region. The finely ground blade made of “Belgian granite”, the Belgian equivalent of Aachen bluestone, was made with ground-in fiberglass reinforcement. The contrast between the darker blade and the lighter handle is enhanced by the different cut, which makes the Belgian bluestone appear particularly dark. For installation, the artwork was anchored on a base stone made of black Swedish in the area of the main entrance.

Art exhibition flanked the trade fair

Because Pauly is a cosmopolitan, art-loving person and the “knife made of natural stone” contains a wink at other materials, an art exhibition with a wide variety of materials was held on his factory premises opposite the trade fair from June 8 – 10, 2018 – in addition to works by sculptors and painters, including steel sculptures by Thomas Röthel and Stephan Mensler. This created a bridge between materials and street sides.

After the event ended, however, the city of Solingen showed no interest in keeping the potential postcard motif in front of the ice rink – so the monstrous knife will soon find a new home with a well-known steelware manufacturer.

12.01.2025

Design

Museum of 1000 Places

Building design

Germany

The Federal Republic of Germany has been commissioning art in architecture for its buildings in Germany and abroad since 1950. Over the decades, around 10,000 works have been created. Natural stone works are also included. Now the Federal Office for Building and Regional Planning (BBR) is making the works of art digitally accessible – via the online platform “Museum of 1000 Places”. In conversation with Dr. Ute […]

Ute Chibidziura: It’s an online presentation for the federal government’s art in construction. In other words, art that is created in connection with construction projects. Since 1950, art in construction has been realized in federal buildings, so that over the years an internationally unique stock of post-war art has been created, which includes the works of many well-known artists in all genres and techniques. We wanted to present this collection of art, which is spread across hundreds of properties in Germany and abroad, in a bundled form.

Many works of art are not accessible to the public …

One peculiarity of art in architecture is that it is tied to the building and is realized in places that are only accessible to a few people for security reasons or, like embassies, are in geographically remote locations. As a result, there are numerous works of art that are little known or have fallen out of sight over the years. With the “Museum of 1000 Places”, we can bring them back into the public eye and make them accessible to the general public.

Why in the form of a virtual collection?

The collection comprises around 10,000 works of art in total. We couldn’t present them in an illustrated book or in an exhibition – that would go beyond any organizational and personnel framework. The “Museum of 1000 Places”, on the other hand, is structured in such a way that works of art can be added bit by bit and the museum grows continuously. In addition, changes can be made to the content at any time. Art in architecture would be difficult to show in a traditional exhibition anyway, because in order to illustrate its location in the spatial context, you would have to build a model of each room or building and prepare picture galleries and texts for it, which would mean an enormous amount of work for just a few examples. Another advantage of a virtual exhibition is that it is not tied to a specific location, but can be viewed from home via the Internet.

How does the digital museum visitor navigate through the site?

There are several ways to access the art: an intuitive one via the images of the artworks on the homepage, a systematic one via the artworks, artists or locations tabs and one via the free text search. Within the artworks, you can sort by technique or context of use.

What information can you find when you call up a work of art?

You will find detailed information about the artwork in its architectural context, about the building and the property, and of course about the artist. It explains the artist’s career, the focus of their work and where else they have realized art on buildings. All information and photos relating to a work of art are stored in the form of a PDF that can be downloaded.

How does the virtual museum build a bridge to the physical world?

The museum indicates whether a work of art is freely accessible or at least open to the public, so that you can also view Kunst am Bau as part of a Sunday stroll. In addition, all works of art will gradually be equipped with a QR code that can be used to link to the “Museum of 1000 Places” to obtain detailed information about the work of art.

Which works of art are made of natural stone?

One important example is the “Rising Phoenix” by Hannes Schulz-Tattenpach on the Old House of Representatives in Bonn. This work of art made of limestone was the first work to be selected and commissioned after the Second World War as part of an open art-in-architecture competition. The phoenix rising from the ashes was intended to refer to the situation of the Federal Republic of Germany at the time, which had to reorganize itself as a democratic state after the war. The motif was still considered so apt in 1974 that it was used as a stamp on a special postcard issued by Deutsche Post to mark the 25th anniversary of the Federal Republic.

You can take a look at the database here: www.museum-der-1000-orte.de.