Thatcham Floods 2007 - I have a theory

This article was first published in the Newbury Weekly News on Thursday 26th July, 2007.

The unprecedented flood scenes in Thatcham resulting from last Friday’s downpour were certainly amazing to those who witnessed them but their aftermath should give us cause for thought. Although I am just a local historian and not a civil engineer, I believe there are lessons to be learned from the way in which the worst effects of the flooding were concentrated in particular parts of the town.

When the Saxons first settled here fifteen hundred years ago, they chose a gravel spur clear of the River Kennet and its sidestreams as the nucleus of their village. Hundreds of years later, Thatcham has been developed beyond that nucleus and the sidestreams culverted and covered over, but their ancient courses remain and are ‘rediscovered’ by nature when excess water is channelled through the town.

That water comes from the high ground to the north of Thatcham - falling on land over 400ft above sea level at Ashmore Green, Cold Ash and Bucklebury - and has to find its way through Thatcham to the River Kennet more than two hundred feet below. In the past it did this through open channels such as the Ashmore Green bourne, the Cold Ash stream and the Bucklebury ‘floush’. In recent times these have all been covered in but they still drain the higher ground to the north.

Last Friday’s torrential rainfall overwhelmed the existing drainage system – but only in certain parts of Thatcham. Whether that was because of the amount of rain that fell or the inability of the infrastructure to cope with it – or both – is an interesting point. Even the brand new pipeline just installed here struggled – manhole covers lifted and raw sewage/toilet paper was disgorged onto the Lower Way playing field! Elsewhere in the town, ‘fountains’ gushed from drain covers.

A look at the historical record shows how things have changed. It is easy to forget the two drainage channels that flow through western Thatcham. The Cold Ash stream ran open down Northfield Road until culverted in the 1920s; south of the A4 it has been completely covered by the Paynesdown Road estate. The Ashmore Green bourne too is now somewhere under the ‘Rivers’ estate, although the current road name “Bourne Arch” reminds us that it passed under the A4 near here.

The view from the A4 Bath Road up Northfield Road with the open channel carrying the stream down its eastern side from Cold Ash being culverted between the wars. Collection of P. Allen.

South of the A4, these two channels continued through what was a “water meadow” – subject to controlled flooding for agriculture – into the nineteenth century! They had a confluence just north of Lower Way, at its junction with Muddy Lane, which leads to the Discovery Centre. As a single stream, they flowed on from here to the Moor Ditch and then into the River Kennet at Monkey Marsh Lock near Thatcham railway station, having dropped over 200ft in barely two miles.

The view from Muddy Lane showing the "Arch" carrying Lower Way across the combined Ash Bourne and Cold Ash streams near the Discovery Centre (c.1900s). Collection of P. Allen.

In eastern Thatcham, the Bucklebury ‘floush’ comes down from Harts Hill and along the eastern side of Dunstan Green – once known as The Marsh, for obvious reasons! It passes under the A4 by the Plough pub in what was once an open channel but is also covered in today. It then drops fourteen feet in the short length of Stoney Lane – if the underground pipe can’t cope with the flow, no wonder the water surfaces and runs waist deep down the road, physically carrying parked cars away with it, as I saw it do last Friday afternoon! I’ve never seen anything like it.

From its junction with Station Road all the way to the railway station, the torrent of water flowed towards the River Kennet on the road surface instead of underground – finding its way into side roads as it went. It did most damage on the Kennet Heath estate, which may have been hit by a double whammy. Old maps show the spring line in Thatcham years ago: the lowest spring marked was at what is now the junction of The Moors and Beancroft roads, but there was another where “Spring Cottages” used to be, now the junction of The Moors and Station roads.

The latter spring fed the Goose Green ditch, which meandered over Thatcham Moors towards Station Road through what was once the Depot site and is now Kennet Heath. Surface water has always collected here: when the Depot was being built in the 1930s the ground was described in a poem as “wet and damp”; after it was demolished the ground was waterlogged, as my photograph of the site in the winter of 2003-4 shows. This weekend there is much surface water on the site although the balance pond is very low – is it actually working yet?

The view looking north-east from the railway bridge across the waterlogged ex-Depot site (now the Kennet Heath estate) as it appeared during the winter of 2003-4. Collection of P. Allen.

Perhaps what happened in Thatcham last Friday is a warning against building on river flood plains and the folly of covering our countryside with concrete? A system that was once perfectly adequate to cope with what nature threw at it is now in danger of being overwhelmed in adverse weather – which, by all accounts we shall face more of in the future. In the past this was not a problem but with the urbanisation of Thatcham it may well become a recurring one if something is not done about it.

Peter Allen, Thatcham

There is a flood map which you can also view (click here). Please feel free to add your comments below to this article.