How pipes and tunnels caused our ‘River of Woe’ to flood

Inside Croydon’s loyal reader, JOHN O’BRIEN is fortunate. He lives on the high and relatively dry ground of Woldingham. From there, he has seen enough to form a view that much of the flooding in the valleys of Kenley and Purley was avoidable, and may even have been caused by modern engineering

Forcing storm waters into underground culverts, as Thames Water has done, will inevitably result in the water forcing itself to the surface after periods of heavy rains

Forcing storm waters into underground culverts, as Thames Water has done, will inevitably result in the water forcing itself to the surface after periods of heavy rains

I have lived in Woldingham since 1985 and have watched the rise and fall of the underground river which flows through Hallilloo Valley, Woldingham. I have also observed the fantasy tales recorded in the media each time it rises above the surface after a period of prolonged rainfall.

The last time this happened was in 2001, and it was foretold in a history of the bourne written by the Bourne Society.

When the rain falls on the hills it drains into the valleys and creates water flows, either underground or most of the time on the surface, and nature takes its course and these rivers take the water from the sky to the sea.

On many occasions when man intervenes in this natural process, he tends to create more serious problems than nature intended. In this case, the flooding of Whyteleafe, Kenley and Purley is man-made and caused by Thames Water’s efforts to channel surface water from the roads into one open culvert.

According to the Bourne Society, from even before Roman times, in this area, “Waters rose unpredictably and the valleys were flooded every few years and the bourne, or ‘woe waters’ as it was often called, gained a reputation far, far beyond its surrounding hills for portending national disasters. Almost certainly the gathering of the flood waters amongst low-lying communities in Croydon was a time of woe and disease for them.

“In the 21st century, with development continuing to spread over the hills south of Croydon and drains and culverts controlling most of the deluges that occur, the rising of the bourne seems – and only seems – to be less frequent. The water that once soaked through the chalk and built up to emerge traditionally every seven years now flows along much of its way north to the Wandle at Croydon and on to the Thames at Wandsworth less visibly through artificial channels.”

The Bourne Society's sketch map of the course of the Woldingham and Caterham Bournes. Note the height figures down the left-hand margin

The Bourne Society’s sketch map of the course of the Woldingham and Caterham Bournes. Note the height figures down the left-hand margin

There are some serious misnomers in some of the coverage of the latest floods.

A bourne is a stream, associated with chalk downland, which only occasionally flows above ground after periods of heavy rainfall.

What is called the Caterham Bourne actually rises under or near the rail viaduct on the Woldingham Road.

Under Stuart Road where it meets the Woldingham Road (by the viaduct) there is a channel to take flood water under the rail viaduct. The water then runs into a gully through the playing field at Marden Lodge primary school.

The gully was dug by Surrey County Council in about 2005 to stop travellers getting on to the field. It has now become a convenient route for water to flow from the Thames Water gully to another Thames Water gully which is located beneath Wapses Lodge roundabout.

That surface water drains into Caterham Valley from Caterham on the Hill, Warlingham and the Woldingham Bourne. From Whyteleafe Valley, the water flows via Kenley Purley and Croydon to the River Wandle and evenutally the River Thames at Wandsworth.

Sadly, Thames Water has constructed underground pipes to drain water to one point at the rear of Whyteleafe Station, where it then flows into a man-made open culvert to drain surface water towards Purley. This system is totally incapable of taking the volume of water flowing into the culvert and as a result it floods over into roads and houses along the way.

Trying to force the bourne into underground culverts, or pipes, as Thames Water has done along the water course from Woldingham to Purley, creates flooding problems at times of heavy rainfall, when the volume of water cannot fit into the piping system

Trying to force the bourne into underground culverts, or pipes, as Thames Water has done along the water course from Woldingham to Purley, creates flooding problems at times of heavy rainfall, when the volume of water cannot fit into the piping system

If the various authorities involved, who now call themselves “Gold Command”, the Croydon Council emergency committee, actually communicated with each other before events like this, the impact could be ameliorated, if not prevented. Even Tandridge Council was handing out leaflets in early January warning of a potential flood.

It seems that once again, Croydon Council never even saw it coming, even though they are downstream from us in Woldingham.

The bourne’s flow has been known to Croydon Council since 1854, when the then Borough Surveyor objected to the construction of the rail link to Oxted and viaduct at Woldingham on the grounds that it would cause flooding when the open valley was enclosed by the viaduct.

There has been so much rain in the past six weeks that flood water is now draining from Woldingham down the rail tunnel to Oxted, where it flows into the River Eden on its way to the Medway. Landslips along the railway line to Oxted, caused by the massive amounts of rain, have seen that line closed for most of this week.

For the residents of Kenley and Purley, another 80 of whom had to be evacuated from their homes overnight, there has been disaster enough from Croydon’s “River of Woe”. If the bourne really does portend further national disasters, as the ancient soothsayers claimed, then we may be in for some very unhappy times.

  • To report rising groundwater levels or flooding, residents are asked to call the Environment Agency Incident Hotline on 0800 80 70 60. You can also sign up to the free groundwater Flood Alert/Warning service by calling Floodline on 0845 988 1188.

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About insidecroydon

News, views and analysis about the people of Croydon, their lives and political times in the diverse and most-populated borough in London. Based in Croydon and edited by Steven Downes. To contact us, please email inside.croydon@btinternet.com
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2 Responses to How pipes and tunnels caused our ‘River of Woe’ to flood

  1. ps does anybody know what happened to the recent-ish plans (2009) to regenerate Purley town centre?

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  2. An interesting but fundamentally flawed article by John. In the south of Croydon highway drainage is a matter for the relevant highway authority and almost exclusively uses large soakaways into the chalk aquifer. Connections to the Bourne are rare. TWU have no involvement in this. Furthermore the upper reaches of the Bourne are the responsibility of riparian (adjacent) landowners who are a mix of private individuals, businesses and local authorities, not TWU. Various sections have been culverted/piped over the years. The capacity of these mainly depends on the size and gradient. If properly designed they can be far more efficient than the open channel feeding them.

    I have been following the efforts to manage the current “rising” of the Bourne and from what is reported in the media I can only conclude that those involved are doing an excellent job – and I can speak with some experience of the issues. Priority, quite rightly, is being given to protecting the water treatment works and several innovative ideas are being implemented. Improving resilience to future events would be expensive but that is a matter for the future.

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