Rainwater as a resource rather than a risk—that is the guiding principle of forward-looking urban design. Rainwater management has long since ceased to be merely a technical side issue; instead, it has become a strategic lever for climate-resilient, green, and livable cities. But how can we make the transition from a sewer system to a “sponge city”? And what role do planners, landscape architects, and local governments play in this transformation? It’s time to rethink rainwater management—as an integral part of urban design and a driving force behind sustainable urban development.

• Why rainwater management today is more than just drainage—and why it plays a key role in urban design.
• The most important technical and design principles of sustainable rainwater management: from decentralized systems to the sponge city.
• Concrete examples from Germany, Austria, and Switzerland that demonstrate how rainwater shapes urban spaces.
• Current challenges: legal frameworks, competition for land, public acceptance, and financing.
• Interdisciplinary collaboration: How planners, city administrations, and citizens work together to develop solutions.
• Rainwater as a driver of biodiversity, microclimate, quality of life, and urban resilience.
• Innovative tools and digital planning instruments for rainwater management in the context of urban design.
• An Outlook: How rainwater management highlights urban transformations and is becoming a trendsetter for sustainable urban development.

From a wastewater problem to a design resource: The new role of rainwater in the city

Anyone discussing urban design today simply cannot ignore rainwater management. While the goal used to be to “drain away” rainwater as quickly and efficiently as possible, we are now witnessing a turning point: Rainwater is now recognized as a precious resource that must be harnessed, stored, and integrated into urban design. Cities face the dual challenge of dealing with the consequences of climate change—heavy rainfall, flooding, and heat islands—while simultaneously creating livable, green spaces. The traditional sewer system, once hailed as a technical masterpiece, has long since reached its limits. It can neither mitigate heavy rainfall events nor improve the urban climate or promote biodiversity.

Modern stormwater management therefore does not begin at the drainpipe but considers water from the very beginning—from the roof to the urban landscape. The vision: Every property, every neighborhood, and every public space becomes part of an interconnected water cycle. Rainwater should be retained, infiltrated, evaporated, or utilized as decentralizedly as possible. The buzzword “sponge city” aptly describes this paradigm shift. A sponge city absorbs rainwater, stores it, and slowly releases it again—just like natural soil.

For planners, this means that stormwater management is no longer just the responsibility of engineers, but also a matter of design, material selection, vegetation, and urban spatial planning. The goal is to make water visible and tangible, rather than hiding it in underground channels. From green roofs to swale-and-trench systems to open waterways—the possibilities are diverse and inspiring.

This new role for rainwater requires close collaboration between urban planning, landscape architecture, engineering, and public administration. Only in this way can solutions be developed that not only function technically but also shape the urban landscape and enhance the quality of life. Cities such as Berlin, Zurich, and Vienna demonstrate that rainwater can become a design element, a resource that shapes identity, and a driver of innovation for sustainable neighborhoods.

But the path to achieving this is challenging. It involves transforming existing structures, mediating competition for land use, and establishing new ways of thinking. Rainwater management is thus far more than a technical discipline—it is a driving force for change in urban design. Those who boldly lead the way here turn necessity into a virtue and transform rainwater from a problem into a design partner.

Technical and Design Principles: From Decentralized Retention to the Sponge City

Implementing sustainable stormwater management begins with a fundamental shift away from centralized, technical thinking. Instead of directing the water as quickly as possible to the nearest wastewater treatment plant, modern concepts rely on decentralized retention, evaporation, and infiltration—keyword: creating retention space. In this process, technical, ecological, and design aspects are woven together into a holistic system.

A key element is the so-called “trough-swale technique.” This consists of shallow, vegetated troughs that collect rainwater and slowly release it into underlying swales—which are ditches filled with gravel. The water infiltrates, is filtered, and enters the groundwater. At the same time, a green, visually appealing element is created in streets or parks that promotes recreation and biodiversity. Even more elegant are open watercourses and urban streams, which showcase rainwater in a deliberate way and guide it through urban spaces as tangible waterways.

Green roofs and facades play a dual role in this context: they store water, delay runoff, and cool the surrounding area through evaporation. In addition, they provide habitat for insects and birds—a real boon for urban nature. Rainwater harvesting systems for irrigating green spaces or flushing toilets are also increasingly being integrated into new construction projects. They not only reduce drinking water consumption but also make water management a tangible experience.

Designing such systems is an art in itself. The goal is to combine technical function with aesthetic quality. Surfaces must be shaped in such a way that they absorb water without causing flooding. Plant selection, soil composition, and materials—all of these must be tailored to precipitation levels, site conditions, and usage requirements. Good examples include the rainwater gardens in Copenhagen and the attractive retention areas in Hamburg’s Oberhafen district, which function as temporary water bodies during heavy rainfall and serve as play and recreational areas in everyday life.

The “sponge city” is not a fixed blueprint, but rather a flexible principle. Every location, every neighborhood needs a tailor-made solution. Thinking in terms of systems is crucial: rooftops, streets, squares, parks, and private gardens are interconnected in such a way that rainwater becomes the unifying element of the urban landscape. The rule of thumb is: The earlier rainwater management is integrated into the planning process, the more effective and cost-efficient the result will be. Anyone who waits until the very end to look for a drainage solution has already lost.

At the same time, the importance of digital planning tools is growing. GIS analyses, hydrological simulation models, and digital twins make it possible to precisely predict stormwater runoff, retention potential, and flood risks as early as the design phase. They help compare alternatives, make optimal use of land, and respond flexibly to changing climate conditions. The digital and green cities are thus converging in the truest sense of the word.

Practical Examples from German-Speaking Countries: Rainwater as Urban Added Value

Theory is all well and good, but what really matters are the built examples that demonstrate how stormwater management can shape urban spaces. In Germany, Austria, and Switzerland, there is now an impressive range of projects that can serve as blueprints for other cities—provided one has the courage to break new ground.

A prime example is the Berlin project “Flussbad Berlin.” Here, a former branch of the Spree River is being transformed into a publicly accessible swimming area. Rainwater from neighboring neighborhoods is pre-treated in near-natural filtration zones before entering the sewer system. The result: a multifunctional urban space that combines water quality, livability, and urban nature. The project impressively demonstrates how stormwater management can enrich urban life—when technical, ecological, and social aspects are considered together.

Hamburg is also setting a good example. In the “Oberhafenquartier” urban development area, retention areas and trough-and-trench systems have been designated as key design elements of the neighborhood. The water features serve not only as functional buffers during heavy rainfall but also as defining elements for recreation, play, and social interaction. Rainwater is viewed as a design partner—not as a disruptive factor.

In Zurich, on the other hand, rainwater is specifically used to cool street spaces. Unpaved surfaces, tree swales, and green spaces ensure that rainwater infiltrates locally, evaporates, and improves the microclimate. The example of “Pfingstweidpark” shows how innovative water management and high-quality open-space design can go hand in hand. The result is attractive, resilient urban spaces that need not fear climate change.

Smaller cities are also making their mark: In Graz, the “Smart City Lab” has been equipped with decentralized water systems that use rainwater for irrigation and evaporation. In Basel, new neighborhoods are featuring multifunctional green spaces that serve simultaneously as rainwater buffers, playgrounds, and biodiversity reservoirs. Such projects encourage us to think outside the box and view rainwater as an opportunity for design.

What all these successful examples have in common is an integrative approach. Planners, city administrations, engineers, and citizens work together on solutions that are ecologically, socially, and aesthetically sound. Rainwater management thus becomes a driver of innovation and identity in urban design—and the key to resilient, livable cities.

Challenges and Prospects: Between Land Use Competition, Public Acceptance, and Digital Transformation

As compelling as these examples may be, the path to widespread rainwater management is fraught with obstacles. In practice, planners and municipalities face numerous hurdles—ranging from legal restrictions and competition for land to a lack of acceptance among investors and users. The central question remains: How can we succeed in establishing rainwater management as a natural part of urban design?

German building codes remain a major obstacle. The requirements for infiltration, retention, and use of rainwater are often complex and vary from state to state. Permit processes drag on, and scope for innovation is limited by technical regulations. Creative solutions, bold public administrations, and close coordination between specialized agencies are needed here to expand the scope for sustainable rainwater management.

Added to this is competition for land. In densely populated cities, land is scarce—every function must compete for its space. Rainwater management is often still viewed as a land-consuming activity rather than a source of added value. This makes it all the more important to develop multifunctional solutions that combine retention, play, recreation, and biodiversity within a single area. This creates synergies that win over all stakeholders.

Acceptance is also a key issue. Building owners and investors often fear additional costs or restrictions on use. Users worry about mosquitoes, odors, or supposedly “wet” areas. The only solution here is transparency, good communication, and a compelling design. When stormwater management is visible, tangible, and attractive, it becomes a defining feature of a neighborhood—not a nuisance.

Digitalization opens up new opportunities. Hydrological simulations, digital twins, and real-time data make it possible to precisely plan, control, and monitor rainwater processes. This allows risks to be minimized, potential to be fully realized, and citizens to be actively involved in design processes. Digital tools make the complexity of stormwater management manageable—and open up new ways to design urban spaces for the future.

The greatest challenge, however, remains establishing stormwater management as a natural part of everyday urban life. This requires committed planners, bold public administrations, and informed citizens. Only when all stakeholders pull together will the vision of the “sponge city” become a living reality. The good news: The tools are here, expertise is growing—and societal pressure to make cities climate-resilient and livable continues to increase.

Conclusion: Rainwater Management as a Future Challenge for Cities and the Landscape

Rainwater management is now at the heart of sustainable urban design. It is far more than a technical requirement—it is a creative, design-oriented, and social project. Those who view rainwater as a resource can make cities climate-resilient, green, and livable. Examples from German-speaking countries show that with courage, creativity, and interdisciplinary collaboration, it is possible to develop solutions that are ecologically sound, visually striking, and enrich urban life.

The future belongs to the “sponge city”—a city that not only manages rainwater but also harnesses it, makes it visible, and integrates it into its very DNA. For planners, landscape architects, and city administrations, this is an exciting challenge. The goal is to combine technical innovation with design excellence, engage citizens, and creatively overcome regulatory hurdles. Digitalization offers new tools for planning, visualizing, and optimizing rainwater management processes.

Those who invest in rainwater management today are shaping the city of tomorrow. It is no longer about drainage, but about enabling urban life—despite, and precisely because of, the water. Rainwater thus becomes a driving force for biodiversity, a catalyst for quality of life, and a link between technology and design.

*Garten + Landschaft* remains at the forefront of this development—with expertise, inspiration, and a critical eye on trends and challenges. Because one thing is certain: The city of the future will not just be built; it will be designed—and water plays the leading role in this.

Urban design and rainwater management are inextricably linked. Those who understand this plan in a resilient, bold, and forward-thinking way. Welcome to the new urban landscape—with rain as a friend, not an enemy.