Blue Green Infrastructure
Nature-based solution for sustainable built environments.
How is blue green infrastructure transforming cities?
Blue green infrastructure (BGI) is a strategic approach to managing water and incorporating natural elements and features into urban spaces. While terms like green infrastructure, water-sensitive design, low-impact design and sustainable drainage systems may sound familiar, BGI uniquely combines "blue" (water management) and "green" (vegetation) elements to deliver environmental, social and economic benefits.
At its core, BGI focuses on developing a harmonious relationship with nature to create sustainable, resilient and liveable cities. From stormwater management systems that double as recreational wetlands to urban forests cooling cityscapes, this approach offers Nature-based Solutions (NbS) to some of our biggest urban challenges.
Why organisations are turning to BGI
Cities across the world are looking to adopt BGI, with these key drivers fuelling the shift:
1. Urban water management
Traditional grey infrastructure, like pipes and drains, focuses on directing water away from urban areas. BGI, however, manages water at its source, using NbS such as bioswales (channels designed to concentrate and convey stormwater runoff while removing debris and pollution), wetlands and permeable pavements. These systems filter water, reduce runoff and improve water quality while supporting existing ecosystems.
2. Climate change mitigation
Climate change is intensifying urban challenges, from frequent flooding to heatwaves. BGI addresses these risks head-on by absorbing stormwater to reduce flood risks, creating urban green spaces to provide shade and lower temperatures, and sequestering carbon dioxide through vegetation.
3. Flood risk reduction
Naturalised solutions like making space for flood plains, urban wetlands and bioswales absorb excess water during heavy rainfall, reducing reliance on grey infrastructure like dams and flood barriers. These systems not only mitigate immediate risks but also offer long-term resilience.
4. Biodiversity
BGI promotes biodiversity by creating and providing habitats for plants and animals in urban environments. This increases the range of species living in our communities and the ecosystem services that they provide, such as pollination and seed dispersal.
5. Urban space enhancement
BGI creates inviting public spaces where communities can come together, improving liveability in cities. Plants can provide shade, lower temperatures and improve air quality, and people benefit from these green spaces through recreation, improved health and well-being.
The challenges of implementing BGI
While the benefits of BGI are clear, its implementation involves several hurdles:
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1. Dispersed systems and maintenance
Unlike centralised grey infrastructure, BGI solutions are often spread throughout a city, requiring holistic planning oversight and more frequent maintenance. For example, bioswales may need regular cleaning, and vegetation in these systems requires management so that it remains a functional part of the system.
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2. Cost perception and quantifying benefits
One of the main barriers to adopting BGI is the perception of higher implementation costs. However, this often ignores the co-benefits BGI offers, such as improved air quality, increased property values and enhanced community well-being. Quantifying these multi-faceted advantages can be challenging but is essential to its broader adoption.
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3. Complex governance
Implementing BGI frequently involves multiple stakeholders, from municipal governments to private developers. This fragmentation can lead to delays, misaligned priorities and difficulty in securing funding.
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4. Public awareness
Because terms like BGI and water-sensitive design are not widely understood, organisations often face challenges in gaining community and stakeholder buy-in. Effective communication about BGI's benefits is crucial for its success.
BGI in action
BGI solutions can be applied at a wide range of scales, from small lot-level interventions to neighbourhood, city-wide and regional (or watershed) scale initiatives.
We work alongside clients across the entire project lifecycle to help integrate BGI solutions at each stage, from early planning and concept design through to detailed design, implementation and long-term management.
Our work in BGI
GHD has been at the forefront of helping organisations integrate BGI into their infrastructure projects. Below are three examples of our work
1. Green rainwater infrastructure for the City of Vancouver
We worked with the City of Vancouver to develop an asset management program for its green rainwater infrastructure. A key challenge was managing 283 dispersed infrastructure assets while planning for future growth under the ambitious ‘Rain City Strategy’.
To address this, we created a scalable, detailed asset management framework, enabling informed decisions about operations, maintenance and expansion. Vancouver now has a roadmap for its Rain City Strategy, supporting sustainable green rainwater infrastructure for decades to come.
2. Stormwater management in Awarua Wetland, Porirua
We developed long-term stormwater management solutions that focused on reducing flooding issues and further contamination of the Te Awarua-o-Porirua harbour. We had to manage stormwater network issues such as insufficient capacity and the lack of secondary flow paths on low-lying flat areas.
Through collaborative planning with a developer and the local council, we helped design multi-faceted stormwater upgrades aimed at providing additional flood resilience in the city centre and stormwater treatment.
The construction of the new Awarua wetland reduced the catchment’s contribution to contaminant and sediment loading into the harbour, enabling the harbour’s remediation, enhancing the urban habitat for native species and mitigating flooding risks. It also provided educational opportunities for the adjacent school and added amenity value for the wider community.
3. Low-impact development in Kitchener, Canada
We worked with the City of Kitchener to replace and reconstruct its roadways, subsurface infrastructure and stormwater solutions, meeting modern urbanisation standards and stormwater retention goals.
The project required phased construction to minimise impacts on residents, schools and parking, and we also had to address significant grade differences and stakeholder coordination.
We provided comprehensive design and construction services, including innovative BGI systems (e.g., StormTree units, bioretention cells) and detailed stakeholder engagement.
This low-impact development upgraded the city’s infrastructure while maintaining parking availability, serving as a successful pilot project for new BGI technology implementation in Canada.
BGI represents a paradigm shift in sustainable development. By integrating natural and engineered systems, it offers a powerful way to address climate challenges, urban water management and biodiversity loss while creating healthier, more liveable cities.
Want to go deeper?
Dive deeper into our Blue-Green Infrastructure. Discover more in the State of Green Infrastructure Asset Management: Benchmarking Report.