Soaking Up The Pressure

Landscape architect associate Jenny Fergusondescribes how an inventive new park is helping to reduce flooding and connect a Manchester community

[All] West Gorton Community Park, Manchester

Manchester has a reputation for being one of the wettest cities in the UK. Climate change is exacerbating this by increasing the frequency of heavy rainfall events. Could a new park which uses a series of swales, rain gardens and bio-attenuation features to direct rainwater away from homes and prevent flooding be the answer?

The final element in a £100m regeneration scheme of 500 new homes, community facilities and school improvements, the lovingly nicknamed Sponge Park opened in summer 2020. It is the first UK demonstrator project for the GrowGreen initiative, funded by the European Union’s 2020 Horizon programme. The project was a result of close collaboration with Manchester City Council, the Guinness Partnership Ltd and the University of Manchester, who will monitor the storm water flows over the next five years to ascertain how effectively the park can reduce flooding, gathering data to inform the design of other green spaces in flood prone areas across the EU. The aspiration is for West Gorton Community Park to be an exemplar; not just an ingenious way to manage water effectively, but to connect community and alleviate the effects of climate change.

Permeable paving for paths allows rainwater to percolate through the ground or channel from surrounding roads to irrigate the new planting. Sounds simple? But permeable pavements require specific materials to ensure the surface acts as drainage yet remains intact; requiring the uppermost layer to provide a stiff surface resistant to wear, while the lower layers spread the load onto the natural ground beneath. We devised a SuDS surface course composed of interlocking concrete block pavers bedded on a layer of 6mm aggregate and wrapped in an impermeable geotextile membrane to create a fully waterproof ‘tanked system’. This composition enables the rainwater to be stored and also controls its release.

Infiltration basins were installed and swales planted to immediately soak up water. Any remaining water flows into sunken rain gardens, planted with a range of nectar-rich vegetation to enhance the natural environment and increase biodiversity. During heavy storms, water is diverted from road and paving gullies into these nature-based features, where planting will naturally filter and absorb the water - significantly reducing pressure on the active drainage system.

A series of headwalls around the water inlet and outlet positions was built using natural stone, which minimises soil erosion. Through the centre of the swales is a series of timber check-dams, to physically slow the rate of water flow. This means the park and the swales act like a sponge, soaking up the water to feed the plants. By the time the remaining water reaches the central rain garden, which is covered by a timber pontoon deck, there is significantly less to manage.

Community consultation identified local needs and aspirations for the open spaces and raised awareness about the impact of climate change. The community has taken pride – and ownership – of the new facility, which promotes social cohesion and wellbeing, together with the significant environmental benefits.

Woodland:

Natural elements such as timber and rock are used in the playground, with objects placed to encourage physical movement and free play. A pebble rill captures water run-off and acts as a play feature for children to follow. Planting along this rocky creek captures and attenuates the water on its journey down to the rain gardens. To the south a sunny glade has been created by removing a dense cluster of existing trees, allowing light to penetrate down to the paths towards the timber seating below. Existing paths have been refreshed with a new surface wearing course.

Meadow:

In parallel with the primary pedestrian path, a sinuous trail with stepping stone logs and beams offers an alternative fitness route for exploration. It travels through the meadow and orchard, with seating niches set into low timber retaining walls, using stepping stones through the rain garden which lead to a story-telling space.

Community:

Open lawns, community planting areas and a south-facing piazza enjoy full community use for events, sports and pop-up markets. Permeable paving filters rainwater through a series of formal channels which irrigates the new trees and plants and provides a rich, sensory environment for the community to enjoy. An open timber structure with acrylic roof catches more rainwater into water harvesting butts beneath, so that there is no requirement to connect to a potable water supply for the watering of plants. Communal raised beds can be used by residents with a keen horticultural interest or who wish to grow their own food.

With increased awareness of sustainable issues and climate change directly impacting people’s lives, the design of community spaces and public realm is more important than ever. At West Gorton, the combination of natural solutions and intelligent permeable materials provides an innovative solution that supports the local community and solves many of the local council’s challenges. The result is a park that reduces flooding in one of the UK’s wettest cities, creates a net gain in biodiversity but most importantly provides a lasting community space where residents can relax, feel safe and ultimately, enjoy as a wonderful space where they can come together.

"The community has taken pride – and ownership – of the new facility"