To find out how extreme rainfall events affect a city, looking at how water moves through the wider catchment is a good place to start. To understand how it interacts with the landscape and vegetation: even better, as plants, soils, trees and other green features may provide solutions to manage surface water drainage that could be part of a smart, sustainable catchment-based strategy for flood management.


Dr Claire Walsh, National Green Infrastructure Facility, Newcastle University

Dr Ross Stirling, National Green Infrastructure Facility, Newcastle University

Professor Richard Dawson, Water Group Head, Newcastle University

Kevin Stott, National Green Infrastructure Facility, Newcastle University

Brett Cherry, Institute for Sustainability, Newcastle University

Built-up environments are part of the water catchment too. Despite their paved surfaces, roads and buildings, water in urban areas behaves the same way as it does in a rural catchment. But in some cases urban catchments are more difficult to manage because water builds up in the infrastructure below ground with no place to go, leading to flooding. It is also much more challenging to store or absorb rainfall on paved surfaces, unless they are made permeable.

This presents challenges for cities which have redirected or eliminated the natural pathways for water to flow. By working with the urban water catchment green infrastructure could make cities more sustainable, allowing them to adapt to climate change, improve air quality and increase biodiversity.

There are few places in the world where green infrastructure features in cities are tested in scientifically rigorous ways. While some cities have incorporated green infrastructure into their planning they may have done so with little if any evidence to justify its implementation. Perceived benefits are not the same as well-tested and trialled ones.

Without a doubt green infrastructure has a role in tackling a range of problems cities are facing, especially surface water flooding. But not all green infrastructure works within every context and the water sector could definitely benefit from real-world data, scenarios and simulations of how green as well as blue infrastructure interacts with traditional grey infrastructure.

This is where real-world demonstrators or ‘living labs’ are important in identifying the attributes of green infrastructure at a range of scales. Data is required for ensuring these benefits are reliable in the short and long term future, making digital sensing invaluable to monitoring urban water catchments.

Cities are unique places for testing catchment strategies for flood alleviation, reducing water scarcity, enhancing ecosystems and sequestering carbon. Blue-green infrastructure has the potential to provide these services and possibly much more, especially when considering evidence that green features enhance property value and citizens’ well-being.

The city of Newcastle has been a demonstrator city for blue green infrastructure since 2013. Working with the local authority, SMEs and Northumbrian Water, both hydrologic and hydraulic modelling of surface water and implementation of blue-green features in the city, were used to develop practical solutions for reducing flood risk in the urban catchment of Newcastle.

The National Green Infrastructure Facility (NGIF) is building upon current and previous research on blue-green infrastructure in cities. Funded by EPSRC through the UKCRIC programme it is based at Newcastle University’s award winning Urban Sciences Building on the Newcastle Helix site, the largest urban development outside of London with research, business and innovation dedicated to helping people live longer, healthier and more sustainable lives.

In collaboration with Northumbrian Water and other stakeholders, NGIF is dedicated to providing proof of concept for green infrastructure solutions in real-world settings. There is no other facility in the country that provides this level of experimental research, demonstration and innovation. It seeks to answer some of the big questions on green infrastructure for cities.

Questions include how well does green infrastructure fare in extreme weather conditions? Are there any reasons for it to be preferred over grey infrastructure? And what knock-on benefits if any does green infrastructure provide? For example, does it alleviate flooding even during the most intense rainfall events? Without researching green features in the field these questions can only be answered anecdotally or in some cases not at all.

In these challenging financial times, the UK water sector, government and local authorities must have reliable data and understanding of what green infrastructure can and cannot provide to cities in order for them to invest in it. It is generally agreed that green infrastructure is not a panacea for flood hazards, nor will it make cities 100% resilient to them. However, it does seem that using green infrastructure when applied appropriately could be one of the most effective forms of flood defence on offer. If this is the case then research in this area could be essential to not only reducing damage to infrastructure caused by flooding, but also potentially save lives.

Combined with digital urban sensing, green infrastructure enables us to interact with urban water catchments at multiple scales. From a systems engineering point of view a tree is no longer simply a ‘tree’ but a node within a wider green infrastructure network that provides basic infrastructure or ecosystem services, such as abstracting water. Soil is highly important as it provides a sink for rainwater. Different types of soil also have multiple sustainability characteristics that could be harnessed for slowing, storing and filtering surface water flows. Soils are also an important carbon sink. An annual growth rate of 4% in the soil carbon stocks would halt the increase in CO2 concentration in the atmosphere related to human activities.

The National Green Infrastructure Facility is testing different ways to use the soil to not only soak up water but to absorb more carbon and to recover and store solar thermal energy for buildings. The research is literally ‘ground-breaking’ and is the first time a facility of this kind is actually part of a city’s fabric. It has implications for urban planning in the city of Newcastle and in cities throughout the UK, if not the world, for testing and demonstrating green infrastructure technologies.

The facility is equipped with ten experimental lysimeters embedded with digital sensing that measure a variety of soils under controlled conditions, including soil moisture, percolation and environmental factors, such as rainfall and drought. Together with in-pavement bioretention features, they make it possible to measure the performance of Sustainable Drainage Systems (SuDS), including water attenuation, storage, treatment and other benefits.

Data from these heavily instrumented features helps us to understand how they function in simulated and real-world storm scenarios. Trees in the facility are fitted with instrumentation to measure how much water they uptake and transpire, monitored with wireless digital sensors. Much of the data generated from the facility will be freely available via the Urban Observatory, a city-wide urban sensing network in the North East of England led by Newcastle University. The Observatory is the largest open digital sensor network in the world.

As extreme rainfall events are expected to increase in the UK according to the latest climate projections, we need to make available as many tools as possible for mitigating flood hazards. Implementing effective green infrastructure solutions to flooding in urban catchments is one of those tools, which may also have large potential to help resolve other problems that nearly all cities have, such as air contamination, over-heating and the need for carbon mitigation. The future of cities using green infrastructure to tackle some of these problems is indeed exciting, and we invite collaborators from the private and public sectors to explore what the National Green Infrastructure Facility may offer to them in addressing these global challenges.

Further info: Urban Observatory