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Grey to Green

A series of inner-city regeneration and transport projects in Sheffield. Reconfiguring roads and pavements (grey) with new pedestrian and cycling provision and flourishing plants (green).

Location:

Castlegate, Sheffield City Centre

Timeframe:

2014–2022

Cost:

£9.9 million. Funded by Sheffield City Region, the European Regional Development Fund and Sheffield City Council, with small contributions from the Canal and Rivers Trust and Yorkshire Water.

Vibrant plants and flowers and people walking past and in groups.
Completed section of Grey to Green Phase 1

Background:

The primary aim of the project was to regenerate an inner city area dominated by roads that no longer carried heavy traffic. Another key aim was to manage surface water more sustainably.

Rain falling on our cities would normally drain quickly into pipes, for example via gulleys in the road. This can add to flooding problems, especially in periods of heavy rainfall. It can also send pollutants such as oils, heavy metals and microplastics from our roads straight to rivers.

A high proportion of urban areas are serviced by combined sewers. These carry both wastewater and surface water. With a changing climate there is an increasing flow of rainwater predicted to enter these sewers. This can lead to an overload of the system. Risks then include sewer flooding or increased pollution into watercourses from combined sewer overflows.

Sustainable Urban Drainage Solutions (or SuDS) are a range of features that receive water and control its release to the river system to manage these risks. This is the urban equivalent of natural flood management. The Grey to Green projects implement a range of SuDS.

Three images side by side. One shows the original road. One shows the work in progress. The final image shows planting beds and trees in place.
Before during and after the configuration of the highway – Credit Grey to Green

Summary of project:

Sheffield City Council transformed a previously tarmacked 1 kilometre length of highway into a linear green public space. Its innovative drainage system captures rainwater and moves it back to rivers in a way that mimics nature – cleanly, slowly, sustainably.

The project created 56 new planting beds called “swales.” Their plants and soil were chosen to create an attractive, colourful vegetation that encourages wildlife. Multi-layered planting, watered by rainfall from surrounding surfaces, helps to protect people and wildlife from air pollution and heat. It also potentially stores carbon in the atmosphere. Through a series of channels and dams, rainwater is held for longer before draining to the river Don in a filtered and controlled manner.

Diagram showing how the planting beds slow the flow of water through dams and planting.
Diagram of Grey to Green sustainable drainage system

A pedestrian path with plants and trees on either side.
Phase 2 – one year after completion

Benefits

  • Improved surface water management. The SuDs planting beds prevents 24,000 bathtubs’ worth of water from entering Sheffield’s sewage treatment works each year.

  • Reduction of up to 80% flow rate in high intensity rainfall events, reducing the pace at which rainfall reaches the River Don.

  • Climate proofing. The project addresses future surface water flooding risk. It also repairs a catchment through allowing infiltration and establishing paths of flow for water into watercourses, all of which mimics nature.

  • A 561% increase in biodiversity value.

  • Special flowerbeds capture pollutants from the road, as well as plastics from car tyres and road wear. This prevents them from reaching the watercourses.

  • 1.3 kilometres of new footpaths and cycleways, encouraging cycling and walking.

  • Economic development. New office and residential developments have taken place in West Bar and Castlegate. There is an improved likelihood for new sites coming forward for development.

For more information:

Visit the Grey to Green website.

Further Information

View projects located in: Sheffield
View similar projects tagged with: Natural Flood Management, Sustainable Urban Drainage
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