Tidal Thames: Bow Creek and the River Lea
The river LEA is an extensive network of waterways, TIDAL and NON-TIDAL, with complex interconnections and a long history of commercial exploitation. Until Summer 2007, it was possible to head North on a rising tide off the Thames into Bow Creek (near the Dome) and keep going ... and going. 10K later, you would still be in salt water, heading across Hackney Marshes, having encountered no locks or obstacles of any sort! Although not regarded as a "navigation", this whole section was de facto navigable to kayaks, and was quietly appreciated by lovers of urban wilderness.
As we write (late 2007) a massive re-engineering exercise is underway in preparation for the 2012 Olympics. This has put the whole Waterworks River section North of Prescott Lock out of bounds and also closed the side branches of the neighbouring NON-TIDAL network (Old River Lea, City Mill River and the Bow Back River). When the protective plastic is peeled off in late 2008, what emerges will be NON-TIDAL, with levels managed by a water control structure alongside the new Prescott Lock. Only the 4K stub from here to the Thames remains unchanged.
Those interested can track progress of the project via these British Waterways pages. British Waterways are of course keen advocates of the project, stressing the benefits of regeneration of this long-neglected area, and of water hygiene. (There are currently regular sewage discharges, evidence for which is seen in the fig trees lining the river banks. Humans eat figs, but the seeds pass through undigested ! "Too much information"?) Elsewhere, there are doubts about the chosen engineering solution, and disappointment at the loss of so much tidal river, as eloquently expressed in this paper from the Regents Network