Turkey Brook has been transformed following a restoration that did one vital thing similar projects often overlook – it reconnected the waterway with its hyporheic zone
As two great white egrets land at the meandering Turkey Brook in north London, it’s hard to believe this thriving river was once mistaken for a ditch.
Located in Enfield’s Albany Park, the river has been transformed following a restoration that did one vital thing similar projects often overlook – it reconnected the waterway with its hyporheic zone.
Perhaps the easiest way to explain the hyporheic zone is by describing it as a river’s liver.
Sitting beneath the riverbed, the porous layer of sediment connects the surface water with the groundwater underneath, supporting the river in cleaning out pollutants and regulating temperature. Teeming with organisms and tiny invertebrates, it provides a sanctuary for biodiversity to thrive. Salmon and trout lay their eggs there.
But too few restoration projects take into account the hyporheic zone and instead aim to save rivers at surface level, by changing its shape or adding some plants.
It is important to remember that rivers “are three-dimensional ecosystems that extend potentially hundreds of metres below the bed,” says Rachel Stubbington, a professor of river ecology at Nottingham Trent University. “It’s inevitable that surface-focused restoration will have limited benefits compared to a project that does also actively try to restore most of the ecosystem, the subsurface a bit.”
At a time when rivers are dying from pollution and degradation due to human activity, experts such as Stubbington are clear that more needs to be done if we want our river-saving efforts to last.
Leading the way is Enfield Council’s work on restoring a 400m stretch of Turkey Brook that ran up the side of Albany Park in 2021. Like many flood-proofed urban rivers, Turkey Brook was lined with concrete, which disconnected the waterway from its hyporheic zone and all the vital functions it performs.
The water was brown and murky, and the only flora was moss growing on the concrete. “People thought it was just a drain or a ditch,” says Dr Matilda Biddulph, a principal geomorphologist at the Environment Agency and committee chair at the British Society for Geomorphology, who was involved in the restoration.
“When it’s in a straight concrete tunnel, you don’t have much habitat, you don’t have any flow variety. All you could really see down there when you looked over the railings was silty water, a few rats and quite a bit of urban litter. It was just really sad.” The team filled in the concrete and dug a new channel for Turkey Brook that meanders through the park. It hasn’t been lined with any impermeable substance, like concrete or plastic, so the river is connected to its hyporheic zone.
Now the water is clearer, and the banks of Turkey Brook are covered in greenery and daisies. Although it was an enormous civil engineering project, Rick Jewell, Enfield Council’s cabinet member for environment, said it will attract wildlife and improve biodiversity. And the surrounding wetland will protect hundreds of local homes downstream from flooding risks.
Dr Biddulph believes Turkey Brook is a good example of how to approach river restoration. “We just dug a very informal ‘starter’ channel, and then allowed the river to create its own form. I think in the last 10- 20 years, river restoration has been very much, ‘We’re going to dig this very specific shape, we’re going to put some gravel here, some plants here. It’s going to be very prescribed so the river can’t necessarily move because we don’t want that footpath to fall in,’ for example,” she said.
“But we gave this river 40 metres of space and said to it, just go. So every time it rains, it floods and it reshapes itself but that’s fine because it has the space to do so until it finds its comfortable form. We call it process-based restoration and I think it’s a really important way of approaching it.”
Source: iNews, Serina Sandhu
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