Could the UK’s new towns be a wash out?

As the House of Lords begins its inquiry into how to practically and effectively deliver the UK’s 100 new towns, deep consideration must be given to how these communities can withstand climate change.

Climate change is no longer a distant threat but a pressing reality. The Met Office reports that five of the UK’s ten wettest years since records began in 1836 have occurred in the 21st century. The decade from 2011 to 2020 was also 9% wetter than the 1961–1990 average, with winter rainfall up by 25%.

Flooding, already one of the most costly and disruptive climate-related risks in the UK, is set to worsen. Therefore, flood resilience must be a non-negotiable feature of these new homes and communities.

From initial statements, the New Towns Taskforce recognises this, stating one of its goals is to create “environmentally resilient places that support the government’s net zero agenda through sustainable design, nature enhancement, low-carbon infrastructure and responsible development, including flood risk mitigation”.

Yet, to deliver on this goal, new towns and communities must be built with a holistic approach to water management, where sustainable drainage systems (SuDS) form a key part of green infrastructure.

Nature-based solutions

While Schedule 3 of the Flood and Water Management Act 2010, which would mandate SuDS in England, is still awaiting full implementation, its principles are readily used in practice. Schedule 3 focuses on managing water runoff in the most natural way possible, slowing down the release of water. This contrasts with more traditional drainage systems, which concentrate on removing surface water as quickly as possible.

Beyond their primary function of improving water quality and reducing flood risk, SuDS offer a wealth of benefits for developments. They can transform public spaces into attractive, usable areas and support biodiversity, a particularly relevant aspect following the introduction of biodiversity net gain (BNG) last year. As a result, SuDS features like rain gardens, swales and tree pits are being used not just for flood mitigation but also for enhancing biodiversity.

Rain gardens, which first appeared in the 1990s in the United States to improve water quality and mimic natural water retention areas, have several benefits for UK housing developments.

Rain gardens significantly improve water quality by capturing and treating surface runoff at the source. As rainwater flows into a rain garden, it is slowed and filtered through layers of vegetation, soil and engineered substrates. This natural filtration process removes pollutants such as sediments, heavy metals, hydrocarbons and nutrients (such as nitrogen and phosphorus) commonly found in urban runoff. The plants and microbial activity within the soil further break down contaminants, reducing the pollutant load before water infiltrates into the ground or is discharged to downstream water bodies.

Rain gardens in particular have increased in popularity among housing developers in recent years. One way to use the rain garden method is to combine it with a kerb, allowing water to flow through an inlet, be slowed down by a diffuser flag and remain at the surface level to be absorbed by the soil. This supports plant life and prevents water from entering the sewer system immediately.

Traditionally, incorporating rain gardens into hard landscaping like this has required bespoke detailing, with design teams often needing to adapt standard kerbs or paving to allow water entry. This bespoke approach has slowed down the process and increased on-site complexity.

However, an off-the-shelf system has been developed to help solve this. It comprises three simple elements that make adding rain gardens to a new development more straightforward than ever.

Combining a left and right-hand inlet and a complementary diffuser flag, it will create both time and cost savings on site when compared to cutting or repurposing standard kerbs. And, due to its modular design, the solution will reduce the margin for error usually associated with bespoke and made-to-measure designs, increasing its effectiveness.

Mansfield District Council

To understand its potential impact on future developments, these rain garden kerbs have been trialled as part of a sustainable flood resilience plan in Mansfield, the largest project of its kind ever attempted in the country.

As part of the scheme, Mansfield District Council and Nottingham County Council have invested £76 million in a range of nature-based solutions to protect communities from flooding. For context, just £15 million has been invested into similar previous projects across the UK.

By the time the project is completed, rain gardens and several other innovative solutions will have played a role in storing over 58 million litres of surface water run-off, reducing the flood risk for 90,000 people in the area.

Intended to be the blueprint for how to manage flooding in the future while also making the area a greener place to live, the project is a showcase of the major impact products like rain garden kerb systems can have on communities as we battle to overcome the catastrophic consequences of biodiversity loss and climate change.

A solution for all

For developers, incorporating flood resilience features is not just a matter of social responsibility but also a smart commercial move. Homes at risk of flooding can be more difficult to insure, harder to sell and more likely to attract post-occupancy issues. This can lead to reputational damage and financial liability.

On the other hand, well-designed SuDS features such as rain gardens and tree pits help reduce the risk of flooding, define a development’s character, contribute to placemaking and appeal to environmentally conscious buyers.

As the UK embarks on its largest housebuilding programme in decades, the opportunity to create flood-resilient, nature-rich communities has never been greater.

Chris Adair is product innovation manager at Marshalls