The River Quaggy
Channelised
The death of a river
"Channelising" rivers means putting them into straight artificial channels. It
usually results in the death of the river and the creation of an ugly, dangerous
drain. All the attractive features of the river, which so often caused people
to settle in the area in the first place are lost. And once a river has had its
natural beauty taken away, interest in the river is lost too.
Why were rivers channelised?
The Quaggy, in common with urban rivers around the world, was progressively channelised as the urban environment encroached upon it. Rivers were channelised to prevent them from flooding. The idea was to build an artificial, straight channel that was much larger than the normal flow of the river. The channel was extra large to allow it to take the biggest flows that would occur during very severe rainfalls. The channel was made as straight as possible so that the water could move away from the area as fast as possible.
Channelising can make flooding worse!
Unfortunately, it was found that moving more water faster only made the flooding far worse downstream. This often resulted in ever bigger channels having to be built, at ever increasing costs. (Look at the size of the channels in Lewisham's town centre.)
Ironically, channelising is now often blamed for some of the worst flooding caused by rivers.
Alternatives to channelising
Natural rivers that can spread out when it rains
Today, engineers try to re-create flood plains where water can sit during big
storms. Often these areas will be enhanced to make up for the places where
flood plains cannot be restored because they have been built on. The water is
stored in the flood plain, rather than rushing downstream and flooding property.
When the storm is over, the stored water gradually returns to the river.
Slow down the rainwater!
Architects can design storm water storage and drains into new developments. These feed rain water more slowly into the river system, reducing the chance of flooding. Water butts also help - they store up water during a rain storm and you can then release it during dry periods when you water your garden.
The other advantage
These methods don't just decrease the frequency of flooding - they also give us back an attractive river that can support life.
Reversing the channelisation of the River Quaggy
Although the Quaggy is an urban river, a very large proportion of it flows through green space. (See the map of the Quaggy catchment.) This means there is a lot of potential to remove concrete channels and recreate flood plains. As well as reducing flooding, this would create some natural beauty in our urban landscape.
The channelised Quaggy
John Roan School playing fields, Greenwich
Downstream end of a concrete channel. The Quaggy in this form presents only a liability to the school. After the 2003/4 restoration, the Quaggy should become a valuable outdoor classroom for Nature Studies, Art, Geography, Science and Biology.
Leathersellers sports ground, Colfe's School, Sidcup Road
Fenced-off concrete channel flowing through a more natural, green strip of land. The channel is clearly oversized for normal flows. These oversized, flat bottomed, vertical sided concrete channels can no longer function as rivers and as such are dead.
View from Manor Road, Lewisham, looking downstream
New channelising - this repair and flood alleviation work was completed in 1991 by the National Rivers Authority (NRA), predecessor to the Environment Agency. No alternatives were offered to residents. It was in response to the NRA's proposal to continue this channelising work along the Quaggy's remaining natural sections that "Friends of the Quaggy" formed, later to become QWAG. QWAG has been successful in saving the Quaggy from future channelising, and is now looking at restoring it from past channelising.
Note also the drain outlet.
Chinbrook Meadows before restoration
In parks it is easier to reverse channelising and restore a natural river, because there is usually plenty of space to work in. Parks, because they are open to the public, are also the places where the maximum number of people will benefit from recreating a river.
This area has now been restored as a result of QWAG's efforts in conjunction with the London Borough of Lewisham, the Environment Agency and local residents. Work was completed in 2002.
River Quaggy near Sidcup Road
With no sticklebacks to hunt for, the only kind of entertainment that children can get from a channelised river is to throw things into it and watch them splash. This kind of channel is much more likely to attract littering and dumping than a natural channel.
Quaggy alongside Grove Park Hospital site
Dangerous, therefore fenced-off. When this site was redeveloped in 1995, the river could have been improved and "naturalised", but this did not happen because the local planning department wanted to preserve these trees. QWAG views this as one of many lost opportunities on the Quaggy.
