On the face of it, only one river runs through the centre of London. But there used to be many more. Before our forefathers carpeted the Thames vale with homes and offices, a network of natural waterways flowed down from the surrounding slopes across several now-drained square miles. Where once were fertile meadows, now hundreds of thousands live crammed together in multicultural streets and highrise estates. Where once were trickling brooks, now Victorian culverts burrow deep beneath snarled-up traffic jams. And where once were meandering lines on a map, now an army of amateur psychogeographers can be found attempting to trace the paths of evocative waterways now hidden from view.
There's a huge swathe of central London where rivers used to be but no longer are. Along the Thames from Wandsworth down to Deptford, the mouths of incoming tributaries have been replaced by a series of storm relief outfalls. In Hampstead Heath or Upper Norwood, a raindrop landing on one side of the watershed will flow downhill in open channel, whereas a raindrop landing the other side will disappear almost immediately from view. There are no riverbanks in Kilburn, Mayfair or Brixton, not any more. Only after exceptional rainfall do these subterranean streams ever re-exert themselves along their former course, bubbling up through drains and leaking into ill-prepared basements. In quieter times nothing short of selective linear demolition can ever raise these rivers back above ground floor level, and no amount of ill-informed bluster from Mayor Boris will ever return London's lost rivers to the surface.
Believe it or not it's now five years since I spent an entire month tracing the path of the long lost River Fleet. I started up at the source, both of them, and followed the route taken by the now-underground river all the way down to the Thames. It remains the most popular thing I've ever written. Countless comments at the time, unexpected contact from blokes who've been down exploring the sewers with boots and torches, and a slew of inquisitive emails ever since from Fleet-hungry folk worldwide. Even last night, while I was writing this, a message landed in my inbox from deepest Welwyn Garden City to say thanks for all the Fleety stuff. No problem, and I bet I enjoyed writing it even more.
It's the maps that intrigue many. You can't see these rivers any more, but where precisely did they go? What's up top where the brooks and bridges used to be, and is there any remaining echo in the placenames and landscape of today? A photograph of a map of the Fleet, hastily snapped on a sodden Farringdon wall in 2004, has become one of my ten most-viewed photos on Flickr. Only true cartographical evidence, such as this, allows us to confirm that the semi-mythological Fleet used to run directly beneath such unlikely spots as Great Ormond Street Hospital and the concourse at King's Cross station.
The definitive book about London's lost rivers remains Nicholas Barton's scholarly tome, published fifty years ago. It's detailed, historical and well-illustrated, but even then fails to dig too deeply into the minutiae of what precisely flowed exactly where. It's certainly no walking guide, unless you count the must-have fold out map [jpg][pdf] tucked into the back of the book.
And so, in the absence of any published replacement, I'm making it my task for 2010 to track and trace the remainder of The Lost Rivers of London. I've done the Fleet, so I won't be doing that again. Which leaves about ten lost rivers to explore, both north and south of the Thames, which I'm hoping to cover at a rate of approximately one each month. And I'll be starting tomorrow with one of the bigger ones. If you can't wait until then, or until December for the last one, here's an alphabetical preview of what's coming up (plus a few useful weblinks to ponder).