The river I grew up splashing in has been quietly disappearing. Just three generations ago it was fuller, wider and longer. From Hatch End to Cowley it was skirted with marsh and decorated with ponds. However – inch by inch, year by year – the river has been shrivelling and the land dehydrating.

The inching pace of this loss makes it a classic example of shifting baseline syndrome, the phenomenon where every generation assumes that the condition of the river they experience is natural, and through this constant redefining of natural conditions, ecological collapse goes unnoticed. Truth be told, the only reason I noticed the degradation of my local river was by playing around with old maps for a GIS assignment.

This is a story about what the River Pinn used to look like, how it changed, and what it could one day look like again.

The Pinn springs into life around Harrow Weald Common, slides round the shallow hills of Eastcote and Ruislip, then down the eastern side of the Uxbridge mound before joining Frays River at the mouth of the Colne Valley.

Like much of outer London, when my grandparents moved here in the 1950s, the land was a quintessential modern suburb. The houses you see today blossomed from the post-war economic boom, quietly usurping the farmland that had been there for one thousand years or two. Sub-urbanisation transformed the Pinn’s sleepy villages into the high streets with double yellow lines we recognise today.

Many of these villages-turned-high-streets have riverine names. Ruislip signifies a place where it is narrow enough to leap across the water, a Rush-Leap. Uxbridge derives from Wixan’s Bridge. Pinner’s original name is Pinnora, -ora meaning hill.

Until recently the Pinn wound its way through Pinner (Pinn-hill), the buildings perching around its banks and bends. When world war came to London the river was dammed at Pinner, and its water rushed across the rest of the city to douse the Blitz. Then, without so much as a thank you, the Pinn was pushed underground.

Today, Pinner’s natural history is suppressed beneath car parks, houses and back gardens. But using historical maps we can see where the water once was.

Ghost ponds haunt garden lawn.

Forgotten river bends explain road bends, drivers unknowingly steering along phantom watercourses.

Below is an interactive map with the old water overlaid. Click here for a full screen version.

Not so long ago there was presumably a marsh around Marsh Road, and enough bryophytes around Moss Lane and Moss Close to justify their namesakes.

Downstream in Eastcote, another stretch of river has been buried and two large ponds have disappeared. Walking past in the summer of 1920, you might have watched towers of mayflies blossoming from the ponds, with swifts pirouetting in to feast.

The Pinn is now 8% shorter around Breakspear, and 19% shorter around Brunel. Just between these two examples this is over 200 metres of river length lost to straightening in recent years.

Where it flows through the old RAF base (now St Andrew’s Park), the Pinn has lost a colossal 78% of its surface area. Where there was once approximately 16,500 square metres of open water, there is now just over 3,500. That is enough water the cover two football pitches, disappearing in less than fifty years.

In just a handful of generations the Pinn has been de-wilded, shrunken, narrowed, filled in, straightened and – perhaps most damaging of all – forgotten.

But it doesn’t have to be like this, rivers can be resurrected. Here are some inspiring examples:

Wandle Park, London

Cheonggyecheon, Seoul

Cornmill Gardens, London

Horseshoe Pond, Norfolk

Ladywell Fields, London

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