Paul Cannaby is director of civil engineering at construction consultancy Pick Everard
Recent years have seen an increase in extreme weather, with severe droughts and major floods in the UK and around the world due to climate change. This requires building flood resilience, but it’s not just about large-scale infrastructure: there’s also great power in natural infrastructure.
“More than 100 ‘rain gardens’ have been built in Cardiff, which are designed to absorb 40,000 square meters of rainwater each year”
In fact, the government has now allocated £25 million to support projects that use nature to increase the country’s flood resilience. This builds on the £15 million Natural Flood Management pilot scheme, which ran until 2021. Across 60 projects supported by this fund, the equivalent of 1.6 million cubic meters of water storage and 15,000 homes were better protected from flooding. Meanwhile, 4,000 hectares of habitat and 610 km of river have been improved, along with the planting of 100 hectares of forest.
So the power of incorporating the UK’s natural landscape into any built environment is obvious.
While targeted funding is welcome, it is only the starting point and every scheme, government funded or not, should consider how we could use nature to our advantage.
Sponge cities
One possible answer to general flood resilience lies in the concept of the “sponge city”. This idea is not to use sponges physically, but to be inspired by the way they absorb water.
Sponge cities incorporate design elements that retain and slow rainwater between its impact on the ground and its return to waterways, thus alleviating situations where heavy rains cause overflows and floods. It is the implementation of green and blue infrastructure in the built environment, covering elements such as permeable pavements, green roofs and napkins.
The model was first seen in China, but adoption is increasing worldwide and can already be found in the UK. More than 100 ‘rain gardens’ have been built in Cardiff, which are designed to absorb 40,000 square meters of rainwater each year.
With that name, it’s easy to assume that this practice is inaccessible. However, it is a common concept and something that is already happening across the country in different forms.
Today, whether it is a green development or a brownfield site, all development is regulated and planning consent would simply be refused if measures were not included to reduce peak run-off water Managing rainfall to prevent flooding poses two challenges: how can we return more water to the ground and how can we slow the return of water to rivers and waterways?
Those working in construction will be familiar with a variety of means such as sustainable drainage systems (SuDS) and mitigation, but we also need to find new ways of thinking. There is also a need to focus on improving the appropriate features in existing developed areas. For example, hammerhead areas in residential developments can be rebuilt with a permeable surface to allow surface water to escape, without affecting the robustness and usability of the road itself.
Elsewhere, storage and vegetation can be implemented as effective tools that also serve to increase biodiversity and appeal, such as the network of ‘living roof’ bus shelters in Leicester. These storage elements again reflect the name “sponge”, with the idea that rain is retained and returned to the system by trickling, unlike traditional drainage that redirects water very quickly.
Early participation
The biggest challenge lies, as always, in existing infrastructure and how to approach development across project teams. Contractors have an important role to play, using their extensive on-site experience to work with clients and project teams to identify opportunities and address potential barriers. Simply put, they can be the enablers for the inclusion of blue/green infrastructure in schemes, a role that will be enhanced when they are involved earlier.
The wider project team has a role to play in the wider education project needed with the public when it comes to water management functions, what they do and how they should work. People are quick to panic or assume something has gone wrong if they see water at ground level, especially with climate change producing different and more extreme weather patterns. However, with increased implementation of SuDS and other blue/green infrastructure elements, this is more often by design, helping to manage water systems and alleviate flooding or damage to infrastructure.
By introducing more of these blue/green infrastructure elements into development projects, especially storage ones, the public will become more familiar with them. But we have work to do to communicate what the benefits are, along with the critical safety considerations and measures that come with introducing water features into public spaces while balancing how they address the impacts of climate change.
