5 lessons learned from blue-green infrastructure delivery

Cities are undergoing a transformation in how they tackle the challenges of climate and environmental change, and are looking towards developing and implementing visions for ‘blue-green’ urban futures.

These are the conclusions of a series of four webinars, 'Blue-green infrastructure: the theory and practice', the ICE East Midlands Chair’s Programme for 2020-21.

Blue-green infrastructure refers to the use of blue elements, like rivers, canals, ponds, wetlands, floodplains, water treatment facilities, and green elements, such as trees, forests, fields and parks, in urban and land-use planning.

Commenting on his programme, Ben McGrath, ICE East Midlands regional chair, said: “Climate change is happening now.

"This means that we, civil engineers, need to look to futureproof the infrastructure we are building today and in the future. Incorporating blue-green infrastructure elements in our designs will help to build more sustainable infrastructure, which is also resilient to climate change and the resulting changing weather."

Blue-green futures project

The programme's four webinars reflect on some of the lessons learned from four exemplar cities with strong blue-green aspirations, and best practice examples of blue-green infrastructure (BGI).

In 2019, we began a project funded by the British Academy as part of the programme on ‘Tackling the UK’s International Challenges’, looking to develop new blue-green futures: where multifunctional blue-green infrastructure (BGI) is delivered by cross-organisational collaborations to address urban water challenges and generate environmental and societal co-benefits. Four cities were selected for analysis:

• Rotterdam, Netherland
• Ningbo, China
• Newcastle, UK
• Portland, Oregon, USA

Each city has different drivers for urban water management, varying approaches to governance, regulations and mechanisms for planning and delivery. These cities are also at the forefront of blue-green implementation in their respective countries, and have established visions (O’Donnell et al., 2021).

We interviewed a range of professionals in the four cities, and reported on findings from an online survey.

Rotterdam, Netherlands

As a low-lying port city situated in the Rhine-Meuse Delta, Rotterdam has a close connection with water. Increasing the city’s resilience to the impacts of future climate change, notably rising sea levels and flooding from extreme rainfall events, is a key priority as outlined in Rotterdam’s climate change and resilience strategies. BGI is a key component of spatial planning to support the transition to greater climate resilience.

Ningbo, China

Ningbo is one of the 30 pilots in the Sponge City Programme, initiated by the Chinese government in 2013. The pilot mitigates flood risk, while storing water to meet future demand by retrofitting existing cities with BGI to facilitate the absorption of rainwater, and subsequent storage, purification and reuse.

By 2020, 20% of urban land in the pilot cities should include ‘sponge’ features: rain gardens, swales - sunken wet or marshy hollows in higher, drier ground - wetlands, ponds, and 70-85% annual precipitation should be managed onsite.

Newcastle, UK

A network of blue-green corridors to capture rainfall in the city centre and transport it to the River Tyne, is a key component of the Newcastle City Strategic Surface Water Management Plan.

The Newcastle Declaration on Blue and Green infrastructure demonstrates the aspiration for BGI, coupled with a change in attitudes, and ways of working towards greater collaboration, while new and retrofit projects, for example, Newcastle Helix and Brunton Park, show evidence of this change.

Portland, Oregon, United States

Substantial investments have been made by government agencies, non-profits, and private landowners, to reduce nuisance flooding, improve water quality, and enhance fish habitat. This includes the ‘Grey to Green’ initiative that widely invested in BGI to alleviate loadings on the piped infrastructure system and reduce adverse impacts on urban watercourses.

Portland has more than 400 eco roofs, over 32,000 street trees, has reconnected and restored urban streams and invested in widespread culvert replacement or removal, allowing water to flow under a road or railway, and downspout disconnection, to allow water to flow directly onto the ground.

Perceptions of BGI

In all four cities, BGI is valued for its positive impact on residents’ quality of life, regarded as providing benefits to flood and water management, water quality, health and wellbeing, biodiversity and urban aesthetics.

The acknowledgement that BGI provide benefits outside of the hydrosphere is a key to the transformation to blue-green futures. BGI is beginning to be regarded as multifunctional, and designed to optimise the delivery of multiple benefits to address each city’s priorities and strategic objectives.

However, the multifunctionality of BGI needs to be a cornerstone of practice and policy to ensure that it provides the greatest benefits, to the greatest number of beneficiaries, and these benefits can be maintained over the lifetime of the infrastructure.

Respondents to our survey identified a range of factors that can improve the uptake of BGI, including increased awareness at all levels - from policymaker to general public. These are:

• wider range of funding
• more BGI in new developments, whether via mandates, planning policy or national/local standards
• increased funding for BGI

Those regarded as driving BGI initiatives differed by city; in Ningbo, the Chinese National Government, which has responsibility for stormwater management in China, is seen as a key driver of BGI implementation, whereas in the other cities, each local or municipal government plays a greater role.

In Rotterdam and Portland, the role of non-governmental stakeholders in driving BGI is apparent. In Portland, communities, non-profits and individual champions are perceived as leading BGI implementation. There is a long-standing tradition of citizen advocacy that has helped push the BGI programme.

In Rotterdam, communities play a key role in decision-making around climate change adaptation and resilience, and are involved throughout the lifetime of projects. This leads to more informed communities, and infrastructure that is designed to deliver benefits that local beneficiaries will value and ultimately desire. Greater community engagement and co-design of projects is a key recommendation.

BGI and net zero

BGI is in the centre of the climate change mitigation-adaptation nexus, by:

• helping reduce greenhouse gas emissions through more sustainable usage of water resources and associated energy
• reducing atmospheric carbon through sequestration (carbon offsetting)
• helping cities adapt to the impact of climate change by:
  • managing flood risk
  • mitigating the urban heat island effect
  • reducing drought risk

For example, by reducing or attenuating runoff, BGI leads to lower volumes of water in combined systems, reducing the flows to sewage treatment works. This leads to energy savings from reduced pumping and treatment.

Managing rainwater at source avoids the large-scale infrastructure to transport the surface water, therefore reducing the carbon footprint. BGI typically has a smaller whole-life carbon footprint compared with grey drainage infrastructure.

The challenge now is to align BGI with net zero initiatives, and ensure that BGI is a key part of the drive to make the UK carbon neutral and able to manage future impacts of climate change.

How can civil engineers support the move towards blue-green, net zero futures?

Monitoring the futureproofing and sustainability of investments in infrastructure delivery and spatial planning is an important role of civil engineers. We must carefully consider the consequences of climate change for future designs.

As civil engineers, we can seize every opportunity to promote the implementation of BGI and sustainable use of water resources in the early stage of the design process of spatial (re)developments.

Hybrid approaches

Besides BGI, hybrid approaches can be an excellent intermediate step. Hybrid approaches combine grey and blue-green infrastructure to maximise water absorption and infiltration and limit costs of green infrastructure, while providing potential co-benefits, for example, net zero. This is partly being driven by legislation, and partly by individual awareness of the benefits of sustainable healthy living (Dolman et al. 2013). For this we must be willing to bridge the gap between disciplines, for example, engineering, planning, governance and finance.

Although climate change and the current Covid-19 pandemic highlights the value of green spaces in cities, the move towards blue-green net zero futures is a transition and needs a step change.

Culture change

In the UK, such a step change will also require a culture change, from seeing water and its supply, transport and drainage as add-on infrastructure, to multifunctional and blue-green infrastructure as an integral part of our living environment. This culture change will initially need to be driven by those of us working in the water management industry, who will need to educate our colleagues in the planning and development sectors, and, from there, raise the awareness of citizens.

Another way of increasing the understanding and awareness of blue-green infrastructure could be to make solutions more obvious to the public, such as increasing the use of above-ground systems.