Rainwater, the gold of the future? Sounds exaggerated, but it’s a bitter reality – at least in cities that oscillate between heavy rainfall and drought. Anyone planning urban areas today without a clever infiltration trench has not heard the shot. Underground rainwater storage is no longer a niche product, but a key building block for climate-resilient architecture and sustainable urban development. But how far along are Germany, Austria and Switzerland? And why is the industry still missing out on the potential that lies dormant beneath every sidewalk?
- Infiltration trenches as decentralized rainwater storage tanks are an answer to urban climate extremes and flooding risks
- Germany, Austria and Switzerland are experimenting with innovative infiltration trench systems – but the breakthrough is yet to come
- Digital planning tools and AI are fundamentally changing rainwater management
- Sustainability and resource protection require technical expertise and interdisciplinary collaboration
- Infiltration trenches influence architectural practice and demand new ways of thinking in urban planning
- Debates about sealing, maintenance and competition for space are slowing down progress
- Global trends such as sponge cities and blue-green infrastructure are setting new standards
- Those who view infiltration trenches as a technical choreChore: Die Chore bezieht sich in der Architektur auf die Anordnung von Fenstern, Türen und anderen Elementen in einem Gebäude. Sie beschreibt die räumliche Verteilung und Ausrichtung dieser Öffnungen und hat Einfluss auf die Lichtverhältnisse und Belüftung im Inneren des Gebäudes. are missing the opportunity to create liveable and resilient cities
Infiltration trenches: from drainage to urban life insurance
Anyone who only thinks of infiltration trenches as gravel pits or temporary construction sites is underestimating the revolution under our streets. Originally designed as simple infiltration aids, modern infiltration systems are now highly developed storage and filterFilter: Ein Material, das bestimmte Wellenlängen oder Frequenzen von Licht oder anderen Strahlungen blockiert oder durchlässt. systems that not only absorb rainwater, but also storeStore: Ein Fenster- oder Türbeschattungssystem, das aus einem Stück Stoff, Jalousien oder Lamellen besteht., clean and release it in a controlled manner. At a time when heavy rainfall events are increasingly paralyzing entire city districts and groundwater levels are falling at the same time, infiltration trenches are becoming urban life insurance. They buffer flooding, relieve pressure on sewer systems and contribute to the microclimate. Anyone who thinks this is all old hat has not recognized the signs of the times. The classic concrete channel has had its day. Today, it’s all about modular, easy-to-maintain and digitally monitorable systems that blend invisibly into the urban infrastructure. The city of the future thinks underground – and not just in the sewage department, but in every architectural design phase.
Germany, Austria and Switzerland are very active when it comes to infiltration systems, but there is no real paradigm shift. While in Scandinavian and Asian metropolises entire districts have long been organized as sponge cities, here in Germany much remains piecemeal. Although there are ambitious pilot projects – from Berlin courtyard districts to Zurich streetcar routes – the large-scale roll-out is faltering. There are plenty of reasons for this: complicated approval procedures, lack of clarity regarding maintenance, competition for underground space and a building culture that struggles with the invisible. Those who cannot see what has been invested are reluctant to pay for it. The result: the technology is there, but the mindset is lacking.
From a technical point of view, infiltration trenches are true all-rounders today. They storeStore: Ein Fenster- oder Türbeschattungssystem, das aus einem Stück Stoff, Jalousien oder Lamellen besteht. precipitation, filterFilter: Ein Material, das bestimmte Wellenlängen oder Frequenzen von Licht oder anderen Strahlungen blockiert oder durchlässt. pollutants, delay runoff and thus protect rivers and lakes. Modern systems have a modular design and can be adapted to the respective topography, soil structure and load scenarios. Sensors and intelligent control systems even make it possible to monitorMonitor: Ein Anzeigegerät, das beispielsweise Bilder oder Informationen aus einem Computersystem darstellt. the fill level in real time and schedule maintenance in a targeted manner. In theory, this sounds like a no-brainer – in practice, it often remains a pilot island solution that is scrapped after a few years. The reason: a lack of interdisciplinary collaboration, a lack of visibility and a planning culture that thinks in squares but not in layers.
However, the real problem is not the technology, but the perception. Infiltration trenches are still seen as a compulsory technical exercise, not as an integral part of urban resilience. Yet as green infrastructure, they could be just as identity-forming for the urban space as parks or squares. Anyone who merely files them away as a cost factor in the specifications is missing the opportunity for innovative urban development.
The international architecture and urban planning debate has long since moved on from this. Terms such as blue-green infrastructure, urban sponge city or nature-based solutions are no longer buzzwords, but tangible strategies that are setting the pace in Shanghai, Copenhagen and Rotterdam. Cities that continue to rely on conventional drainage are building themselves into a dead end. Those who rely on decentralized, flexible and smart rainwater storage, on the other hand, are investing in the future viability of their city.
Innovation and digitalization: the infiltration tank becomes smart
Ever since Smart City and Building Information ModelingBuilding Information Modeling (BIM) bezieht sich auf den Prozess des Erstellens und Verwalten von digitalen Informationen über ein Gebäudeprojekt. Es ermöglicht eine effiziente Zusammenarbeit zwischen verschiedenen Beteiligten und verbessert die Planung, Konstruktion und Verwaltung von Gebäuden. (BIMBIM steht für Building Information Modeling und bezieht sich auf die Erstellung und Verwaltung von dreidimensionalen Computermodellen, die ein Gebäude oder eine Anlage darstellen. BIM wird in der Architekturbranche verwendet, um Planung, Entwurf und Konstruktion von Gebäuden zu verbessern, indem es den Architekten und Ingenieuren ermöglicht, detaillierte und integrierte Modelle...) arrived in German engineering and architecture firms, a breath of fresh airAIR: AIR steht für "Architectural Intermediate Representation" und beschreibt eine digitale Zwischenrepräsentation von Architekturplänen. Es handelt sich dabei um einen Standard, der es verschiedenen Software-Tools ermöglicht, auf eine einheitliche Art auf denselben Datenbestand zuzugreifen und ihn zu bearbeiten. has been blowing through the world of rainwater management. Infiltration trenches are no longer only planned in analogue form, but are now recorded, simulated and optimized as part of digital city models. What used to disappear underground as reactive power is now a data set with coordinates, capacity values and maintenance intervals. Digitalization makes possible what even the best engineers could only estimate in the past: precise, predictive control of the urban water cycle.
AI-supported simulations calculate the impact of rain events throughout the year, where there are critical bottlenecks and how structural changes affect water retentionRetention: Die Fähigkeit eines Materials, Wasser oder Feuchtigkeit aufzunehmen und zurückzuhalten.. This is not a luxury, but a survival strategy for cities that do not want to end up in a state of emergency every time there is a summer storm. Digital twins integrate infiltration systems as well as roads, buildings and green spaces. Those who take digitalization seriously think not only in terms of buildings, but also in terms of processes and systems. The construction site becomes a data source, the city a learning organism.
Germany, Austria and Switzerland are certainly active in the digitalization of water management, but the big picture is still missing. While entire city districts are monitored and controlled in real time in Copenhagen or Singapore, data protection and responsibilities are still being discussed in Germany. Many local authorities shy away from the complexity, others fear a loss of control. The result: isolated solutions, fragmented data silos and a patchwork of different systems. However, those who take the plunge into the digital age can save resources, reduce operating costs and extend the service life of the infrastructure.
Digitalization is also changing everything in planning practice. Architects and engineers have to learn how to use new tools and data formats. Anyone creating BIMBIM steht für Building Information Modeling und bezieht sich auf die Erstellung und Verwaltung von dreidimensionalen Computermodellen, die ein Gebäude oder eine Anlage darstellen. BIM wird in der Architekturbranche verwendet, um Planung, Entwurf und Konstruktion von Gebäuden zu verbessern, indem es den Architekten und Ingenieuren ermöglicht, detaillierte und integrierte Modelle... models must create infiltration trenches as objects with attributes and interfaces. Anyone designing urban open spaces has to think about water management as an integral component – from the green roof to the retentionRetention: Die Fähigkeit eines Materials, Wasser oder Feuchtigkeit aufzunehmen und zurückzuhalten. body under the parking lot. This makes the planning profession more complex, but also more exciting. Anyone who refuses to embrace digitalization is planning past reality.
However, digitalization also opens up new opportunities for participation and transparency. Citizens can understand how their city deals with rainwater, what measures are planned and where there are risks. Open data initiatives and visualization tools are turning the invisible underground into a topic for the public. Those who use the digital transformation wisely get the urban community on board and create acceptance for necessary investments. In short: without digitalization, the RigoleRigole: Eine Rigole ist ein Bodenfilter, der zur Versickerung von Regenwasser eingesetzt wird. remains a foreign body – with it, it becomes an integral component of the sponge city.
Sustainability, technology and the battle for the subsoil
Infiltration trenches are considered a prime example of sustainable urban development – at least on paper. They promote groundwater recharge, prevent flooding and support the urban microclimate. Sounds good, but as always, the devil is in the detail. In practice, numerous technical, ecological and social challenges have to be overcome. It starts with the right location: Not every soil is suitable for infiltration, and not every district offers enough space for extensive storage systems. There are also questions of load-bearing capacity, maintenance and life cycle costs. Anyone planning infiltration systems needs to know what loads the subsoil can withstand, how filterFilter: Ein Material, das bestimmte Wellenlängen oder Frequenzen von Licht oder anderen Strahlungen blockiert oder durchlässt. materials age and how to minimize the inflow of pollutants.
The interfaces with other infrastructures should also not be underestimated. In the subsoil, infiltration trenches compete with pipes, foundations, parking garages and roots for every cubic centimetre. The famous civil engineering coordinate becomes the crucial question: who has priority in the urban subsoil? Many cities lack a coordinated management system that systematically integrates all uses. The result: expensive rescheduling, conflicts on the construction site and, in the worst case, non-functional storage facilities that never go into operation. If you want sustainable solutions, you need interdisciplinary teams that work together from the outset – from urban planning to landscape architecture and civil engineering.
Another problem: maintenance and operation are often underestimated. Infiltration systems are not self-sufficient. Without regular checks, filters become clogged, sediment builds up and effectiveness drops dramatically. Local authorities and owners must be prepared to invest in monitoring and maintenance. Digital sensor technology can help, but it is no substitute for qualified specialists. Those who focus on sustainable effects must also ensure long-term maintenance.
The legal framework is another minefield. Although there are numerous standards and recommendations for the construction and operation of infiltration systems in Germany, Austria and Switzerland, implementation is often patchy. Responsibilities are unclear, approval procedures are complex and liability issues are not conclusively clarified. If you want innovative solutions, you must also have the courage to question rigid regulations and make use of the leeway available.
In the end, however, it is not the technology that is decisive, but the interplay between planning, operation and acceptance. Infiltration trenches are not a magic bullet, but they are an important building block for climate-adapted cities. Those who seize the opportunities and master the challenges can make a decisive contribution to urban resilience. Those who get lost in the jungle of regulations or technical details risk falling back into a concrete jungle.
Architecture in the sponge city: new roles, new responsibilities
The integration of infiltration trenches and decentralized rainwater storage systems not only changes the infrastructure, but also the role of architecture. Buildings, districts and open spaces must now be considered as part of an urban water cycle. Those who continue to design only roofs and façades are ignoring the most important resource of the future. The demands on planners are increasing: Material selection, terrain modeling, retentionRetention: Die Fähigkeit eines Materials, Wasser oder Feuchtigkeit aufzunehmen und zurückzuhalten. volumes, hydraulic calculations and monitoring – everything becomes part of the design responsibility. Architecture is becoming more technical, but also more relevant. Anyone who does not speak the language of engineers becomes an extra in their own design.
At the same time, the sponge city strategy opens up new design freedoms. Trenches do not have to remain invisible. They can be staged as part of parks, squares or streetscapes – as watercourses, troughs or retentionRetention: Die Fähigkeit eines Materials, Wasser oder Feuchtigkeit aufzunehmen und zurückzuhalten. basins. Making the technology visible creates identity and awareness for the use of resources. The city becomes a stage for water, climate and the circular economy.
Cooperation within the planning team is also changing. Landscape architects, urban planners, building physicists and civil engineers must all pull together. Interface management, data integration and iterative design processes are becoming an everyday challenge. Those who entrench themselves in silos will lose touch. However, those who are open to new ways of thinking can develop innovative solutions that are both technically and aesthetically convincing.
The global discussion about blue-green infrastructure and nature-based solutions has long since reached German-speaking countries. International projects set standards against which domestic building culture must be measured. Anyone who believes they can get away with minimum standards and mandatory programs will be caught up in reality. The sponge city is not a utopia, but a necessity. Those who fail to implement it are building against the future.
In the end, it’s about more than just technology. It’s about responsibility, innovation and the courage to break new ground. Infiltration trenches are a symbol of the transformation of the city – from a concrete sewer to a living landscape. Anyone who gets involved in this not only shapes the infrastructure, but also the self-image of the architecture. The future of the city lies underground – and in the hands of planners who are prepared to rethink.
Conclusion: Those who do not plan infiltration trenches today will be left out in the rain
Infiltration trenches are far more than just technical stopgap solutions. They are the backbone of sustainable cities – invisible but indispensable. Germany, Austria and Switzerland have the know-how, but lack the courage and vision. Digitalization offers new tools, sustainability requires new ways of thinking and architecture must take responsibility. Those who continue to rely on conventional drainage will be overtaken by reality. Those who rely on clever rainwater storage, on the other hand, will build the city of tomorrow – resilient, liveable and ready for the next downpour. The sponge city is not a trend, but the order of the day. Anyone who ignores this will literally be left out in the rain.