Saturday, July 12, 2008

Exhuming London's rivers

There are dozens of rivers in England's biggest city besides the Thames. But because nearly all of them have been buried in underground drains or converted to sewers over the centuries, even most Londoners know nothing about them.

Now, London's new mayor, Boris Johnson, has proposed that the city work to unearth parts of its historic tributaries to the Thames, as part of a broader scheme to introduce more parks and open space into the city.

Some river daylighting projects have already been accomplished, thanks to the activism of local watershed councils. In southeast London, the Quaggy Waterways Action Group prevailed in bringing a short stretch of the River Quaggy to the surface in Sutcliffe Park:

The restoration project came about when the city proposed a conventional concrete channel to carry the river through the park in 1990. But concrete channels, in aggregate, tend to worsen flooding by rushing rainwater downstream all at once, instead of letting it spread out and sink into the ground along floodplains. The Quaggy Waterways Action Group showed that restoring the riverway through the park would be more effective in controlling floods and less expensive than underground pipes and drains.

Apparently it took the citizen activists 14 years to convince the civil engineers, but good sense prevailed and the waterway was restored in 2004. Apparently, Mayor Johnson was impressed with the results.

The mayor's advisers "believe that unearthing stretches of buried rivers and creating new parkland could help to cool the capital, which can get markedly hotter than the surrounding suburbs." But Londoners can also expect waterway daylighting projects like the one in Sutcliffe Park to also restore wildlife habitat, provide recreation areas for its neighbors, and help improve water quality throughout the Thames watershed.

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