Whenever somebody asks me what’s the best example of urban river restoration you know? I always tell them about the upper Wandle.
Right across the road from my own front door, the ancient weir at Butter Hill Mill has probably impounded this stretch of chalkstream for at least 700 years. By the nineteenth century, a complex of foundries, paper mills, corn mills and watercress beds had emphatically erased all vestiges of the river’s original upper course.
At least two of these sites were eventually converted into chemical factories, and the picturesque old millpond was canalised into a single concrete culvert through BP’s Mill Lane works. According to long-time local residents, cages of trout were periodically suspended in this channel to test the water quality. The sooner they died, the more urgently someone needed to check the discharges of hydrocarbons and vinyl compounds into the river…
But when the factories finally closed around 1995, and the area began to be redeveloped for housing, the newly-formed Environment Agency grasped the opportunity to try some real river restoration. After more than a metre of contaminated soil had been scraped off the whole site, project manager Dave Webb began rebuilding the river from the gravels up: replacing one concrete bank with gabion baskets, regrading the other and planting willows, poplars, sedges and other riparian vegetation. Ranunculus, watercress, forget-me-not and mint drifted down from Grove Park, and the gravels were colonised by bullhead, stickleback and stone loach.
Fifteen years later, this stretch of the Wandle is still one of the biggest paradoxes we know. Highly urbanised and horribly over-abstracted, only the local water company’s unique recirculation system actually keeps it flowing at all – yet you can almost guarantee to see a kingfisher flashing along this cool green corridor any day of the week, and the Butter Hill wheel pool holds a small population of determinedly spawning Trout in the Classroom graduates.
As a result, the Wandle’s Carshalton arm probably represents the region’s first best hope of getting an urban water body up to Good Ecological Potential for the purposes of the Water Framework Directive, and the Wandle Trust and Wild Trout Trust have been steadily enhancing this whole reach over the past two years: reducing small stilling weirs to improve fish passage, installing large woody debris and more than 60 tonnes of gravel, and generally trying to max out the habitat in preparation for kick-starting a self-sustaining population of truly wild trout.
In short, as Dave’s before and after photos show… given time and determination, there’s quite literally nothing you can’t do to rebuild an urban river…
(Photos: thanks to Dave Webb)