Blue/Green Cities

In many cities, nature is fragmented, and stormwater is treated as a problem. Blue-Green Cities aim to change this by connecting parks, wetlands, rain gardens, and streams into continuous networks. These connected systems help water flow naturally through urban areas while supporting habitats and human recreation.

This approach reduces flood risks, improves air quality, and creates walkable, enjoyable spaces. Instead of hiding water in pipes, it is celebrated and used as a design element.

In the city of Melbourne, Australia, the Moonee Ponds Creek was once a concrete channel, but recent efforts have begun transforming it into a chain of wetlands, green corridors, and recreational trails. These connected blue-green spaces now help manage floods and provide bike routes and bird habitats.

Have you seen a park or street where water and plants are used together to make the space more enjoyable?

In a natural landscape, most rainwater is absorbed into the ground. But in a city full of concrete and asphalt, rain quickly becomes runoff, water that flows over surfaces and overwhelms drains. This causes flooding and pollution. Blue-Green Cities try to mimic the natural water cycle. Features such as green roofs, permeable pavements, bioswales, and wetlands help rainwater soak into the soil, evaporate, or slowly seep into nearby water bodies. This method is known as sustainable urban drainage or low-impact development, and it works in harmony with nature instead of against it. In Berlin, Germany, the Rummelsburg neighborhood was designed with permeable walkways, stormwater gardens, and green courtyards that allow rain to seep into the ground. Even during heavy storms, these areas prevent street flooding and reduce the load on the city’s sewers. Can you imagine how different your street would look if rain could soak into the ground instead of rushing down the gutters?

Blue-Green solutions do more than manage water. They improve quality of life. Trees and plants cool cities, reduce energy use, and capture carbon dioxide. Green spaces improve mental health and increase physical activity. Cleaner waterways support fish, birds, and insects, boosting urban biodiversity. Studies also show that well-designed Blue-Green areas can raise property values and reduce the cost of infrastructure maintenance over time.

In New York City, the High Line, a former elevated rail track turned into a green walkway, not only manages rainwater through its planting system, but has also become a significant attraction. Property values around the park increased, and the area saw economic revitalization alongside ecological improvement.

If your city had more greenery and clean water spaces, how would your daily life feel different?

Designing Blue-Green Cities isn’t guesswork; it involves careful study. Planners use hydrological models to simulate how rainwater behaves across different surfaces and during storms. These tools help determine where water flows, where flooding is likely to occur, and where interventions can have the most impact.

Combining this data with maps, population density, and climate trends allows cities to create resilience strategies that prepare for future challenges, like intense storms or long dry periods. In Rotterdam, engineers utilized flood prediction models to identify low-lying areas that were vulnerable during extreme rainfall events. This led to the creation of “water plazas"—sunken public squares that stay dry most of the time but temporarily store stormwater when needed.

Why do you think it’s important to plan for water, even if your city doesn’t flood often today?

Blue-Green design requires a new way of thinking about space. Instead of treating water as separate from city life, it becomes part of the urban experience. Parks may double as flood zones. Streets may include swales to guide water into planting beds. Buildings may have green roofs to capture rainfall.

This vision comes from landscape urbanism, a design approach that uses natural processes, like water flow and plant growth, as the basis for planning cities. In Singapore’s Bishan-Ang Mo Kio Park, a once-concrete drainage canal was transformed into a meandering river surrounded by parkland. The space now supports wildlife, reduces flooding, and provides a peaceful gathering place for residents.

Would you prefer a neighborhood designed around nature and water, or one built only around traffic and buildings?

Once designed, Blue-Green systems must be built and maintained. Materials must be both durable and environmentally friendly. Maintenance teams must keep wetlands clean, maintain healthy vegetation, and ensure that water channels remain unblocked. Cities often use life cycle assessments to track the long-term costs and benefits of these systems. This ensures that the solutions are not only good for the environment but also affordable and practical for years to come.

In Philadelphia, the “Green City, Clean Waters” program tracks the performance and cost of over 1,000 green stormwater infrastructure projects. Regular maintenance ensures they continue to work and collect reliable data, which helps justify future investment.

What do you think is more challenging, building new systems or making sure they keep working well?

For Blue-Green Cities to succeed, people need to be involved. Local governments must enact strong policies, but communities must also play a role in shaping and supporting these projects. Sometimes, residents help care for rain gardens or take part in “adopt-a-green-space” programs. It’s also essential to make sure Blue-Green benefits are shared fairly. Good design considers all communities, not just wealthy ones. This leads to more just and inclusive cities.

In Medellín, Colombia, the “Green Corridors” project introduced trees, shaded walkways, and stormwater management systems into low-income neighborhoods, enhancing safety, mobility, and environmental health throughout the city.

If your neighborhood had a say in designing a new green space, what would you want it to include?

Woodstock, Illinois, stands out as a model of environmental consciousness in a small-city context, embodying many principles of the Blue-Green Cities framework. The city’s 2020 Vision Statement defines Woodstock as a “Connected Green Community” focused on protecting natural resources, promoting sustainable development, and fostering ecological resilience. At the core of its strategy is a Green Infrastructure Plan that maps out networks of trails, buffer zones, and preserved natural areas, creating a framework that guides future growth while conserving the landscape. Public parks, such as Emerson Park, Ryder’s Wood Park, and the Donato Conservation Area, serve both ecological and social functions, blending recreation with habitat protection. On the energy front, Woodstock is home to a 2.9 MW community solar farm featuring over 7,700 panels that supply renewable power to hundreds of homes. Residents benefit from tax credits and incentives to adopt solar energy systems, and the local school district is exploring the use of solar energy credits for its operations. Recycling is another pillar of sustainability in Woodstock. The city operates a comprehensive recycling program with single-stream collection, offers additional recycling options for items such as Styrofoam and holiday lights, and maintains continuous public engagement to reduce waste.

What aspects of your city or neighborhood could benefit from Woodstock’s blue-green approach?

The Coulée Verte René-Dumont, also known as the Promenade Plantée, is a visionary Blue-Green space built on an abandoned railway viaduct in Paris. Stretching 4.7 kilometers, it connects neighborhoods through a lush elevated park filled with native plants, shade trees, and walking paths. This green corridor not only cools the city and improves air quality but also absorbs stormwater and supports pollinators, vital elements of urban biodiversity.

What makes the Coulée Verte especially compelling is its integration of ecological function with cultural life. The arches below the viaduct house artisan shops and galleries, showing how reusing infrastructure can serve both people and the environment. Its success inspired similar projects worldwide, including New York’s High Line, and positions it as a flagship example of Blue-Green urbanism.

Could your city repurpose an old road, rail line, or industrial site as a space for both people and nature?

• What is the main goal of Blue-Green Cities?
  • To remove all water features from cities
  • To build more concrete channels for water
  • To connect parks, wetlands, rain gardens, and streams into continuous networks
  • To keep water hidden in underground pipes
• What do Blue-Green Cities try to mimic?
  • The natural water cycle
  • Urban architecture styles
  • Traffic patterns
  • Sewer construction techniques
• What is one benefit of Blue-Green areas besides water management?
  • They increase traffic speed
  • They reduce physical activity
  • They make cities more crowded
  • They cool cities and improve mental health
• What do planners use to understand how water moves in cities?
  • Thermometers
  • Hydrological models
  • Traffic cameras
  • Concrete mixers
• What design approach guides Blue-Green planning in cities?
  • Traffic engineering
  • Classical architecture
  • Landscape urbanism
  • Modernist urbanism
• What design approach guides Blue-Green planning in cities?
  • Traffic engineering
  • Classical architecture
  • Landscape urbanism
  • Modernist urbanism
• What do cities use to track the long-term costs and benefits of Blue-Green systems?What do cities use to track the long-term costs and benefits of Blue-Green systems?
  • Tax records
  • Life cycle assessments
  • Building permits
  • Police reports
• What helps create more just and inclusive Blue-Green Cities?
  • Building only in wealthy neighborhoods
  • Ignoring local feedback
  • Designing for all communities
  • Removing public parks
• What is the core strategy behind Woodstock’s environmental planning?
  • Replacing parks with parking lots
  • Reducing the number of trees
  • Building more roads
  • A Green Infrastructure Plan
• What was the Coulée Verte built on?
  • An abandoned railway viaduct
  • A shopping mall
  • A concrete flood canal
  • A train line