Blue-Green Infrastructure
How nature cools and protects the city from flooding
What it is – in one sentence
Blue-green infrastructure (BGI) is a network of water ("blue") and vegetation ("green") within the urban environment that complements or replaces conventional grey infrastructure, helping cities better manage rainfall, heatwaves and drought.
Instead of directing rainwater immediately into the sewer system, it is retained where it falls—in vegetation, soil and small retention features. This also creates greener spaces, provides shade and improves air quality.
Where the name comes from
- The "blue" element refers to water, including ponds, retention basins, swales, drainage channels and rainwater storage systems.
- The "green" element includes vegetation such as trees, shrubs, lawns, wildflower meadows, green roofs and living walls.
These two elements work together: water sustains vegetation, while vegetation retains and naturally filters water.
Four key benefits
1. Less flooding. During heavy rainfall, conventional drainage systems can quickly become overloaded. Vegetation and permeable surfaces absorb part of the rainfall, reducing the amount of water entering the sewer network and slowing surface runoff.
2. A cooler city. Concrete and asphalt absorb and retain heat, creating the urban heat island effect. Water and vegetation act as natural cooling systems by providing shade and cooling the air through evaporation.
3. Water available during droughts. Rainwater stored in soil and retention features remains available for vegetation and groundwater recharge instead of flowing directly into rivers.
4. Cleaner air and healthier ecosystems. Vegetation naturally filters air and water while creating habitats for birds, pollinators and other wildlife. Green urban spaces also make cities more attractive and enjoyable places to live.
What it consists of – practical solutions
Blue-green infrastructure consists of many interconnected elements distributed throughout the city, including:
- Rain gardens that collect and gradually absorb runoff from roofs and paved surfaces.
- Bioretention basins and swales that temporarily store and filter rainwater.
- Retention ponds and reservoirs that store larger volumes of water.
- Permeable pavements that allow rainwater to infiltrate into the ground.
- Green roofs and living walls that reduce heat and retain rainfall.
- Trees, shrubs and wildflower meadows that provide shade, cooling and increased biodiversity.
Blue-green acupuncture, one of the measures implemented under the Swiss-funded programme in Grudziądz, consists of small-scale interventions in selected urban locations, such as public squares, green spaces and street sections.
How it works in Grudziądz – the "Let's Make a Difference" project
The development of blue-green infrastructure is one of the project's key priorities. Planned measures include:
- The revitalisation of Podworski Tarpno and Kuntersztyn parks, creating more green space, improving water retention and enhancing recreational areas.
- Blue-green acupuncture in selected locations, including Independence Square, Mickiewicza Street, Kwiatowa Street and the former Jordan Garden.
- The redevelopment of areas along the Trynka Canal, Herman Ditch and around Primary School No. 18.
- The stabilisation of the Trynka Canal embankments combined with water retention measures to reduce flood risk.
These measures will increase the amount of green space in the city (currently covering less than 20% of its area), reduce the risk of flooding, create a cooler urban environment during heatwaves and improve the quality of public spaces.
What you can do at home – blue-green infrastructure in your garden
Blue-green infrastructure can also be introduced in your own garden or even on your balcony:
- Create a rain garden by directing roof runoff into a planted depression instead of the sewer system.
- Install a rainwater storage tank and use collected water for irrigation.
- Reduce paved surfaces by choosing permeable materials and increasing green areas.
- Plant trees and shrubs, which provide shade and naturally retain water.
- Replace traditional lawns with wildflower meadows, reducing maintenance while improving biodiversity and water retention.
In summary
Blue-green infrastructure brings water and vegetation back into the urban environment instead of relying solely on concrete and pipes. It helps retain rainwater where it falls, making cities more resilient to flooding, cooler during heatwaves, better prepared for drought and more pleasant places to live. In Grudziądz, it is one of the key ways in which the "Let's Make a Difference" project supports climate change adaptation, and every resident can contribute to these efforts.