Learning from freak weather events

In the summer of 2007 the town of Thatcham in West Berkshire, like other towns across the country, suffered flooding on a scale not seen before. In Thatcham it was unprecedented because many homes there were flooded for the first time, and the rainfall that caused it had never been experienced in living memory.

Flash flooding
On the afternoon of 20 July, torrential rain inundated the town in just a few hours and, crucially, the sloping fields above it. The result was a volume of water that the drainage system simply could not cope with. Something approaching 1,000 properties suffered flooding of some sort, with some homes remaining uninhabitable for months afterwards.
Much of the flash flooding that occurred was caused by the huge amounts of rainfall on the hills to the north of the town, running down to the properties below, unable to be collected by the surface-water sewerage system that was already at capacity from rainfall on the town itself.
The floods had taken everyone by surprise and the subsequent investigation, spearheaded by civil engineers at West Berkshire Council, resulted in the drawing up of a surface water management plan, many smaller elements of which were put in place as soon as feasible. Most important to the plan, however, were designs for three substantial dry reservoirs above the town, the first of which has now been built.

Attenuation basin
This flood ‘attenuation basin’ has been constructed at Cold Ash Hill, north of Thatcham. The scheme comprises a 1.7 hectare basin surrounded by a raised earth embankment which acts as the required reservoir.
The idea is very straightforward. As Stuart Clark, principle engineer at West Berkshire Council, says: “The pond collects and stores surface water run-off from the rural catchment above Thatcham. Once the storm has passed, the water can then be released at a rate the underground sewers can accommodate.
“Storing the water and releasing it at a controlled way, prevents the sewers becoming overwhelmed and surface water flowing over the ground, which was what caused the flooding in 2007.”
Far from being a blot on the landscape the structure has been designed to blend in with its surroundings. The reservoir will normally be dry apart from one corner which will be permanently marshy and planted to provide wildlife habitats. Over time, the rest of the area will become grass and vegetation like the surrounding countryside
The scheme is designed to provide protection from a ‘once in a hundred year storm’ such as that which caused the flash flooding seven years ago. Designs for further attenuation basins at Tull Way and Dunstan Park above the built up areas are now being finalised.

Helping people help themselves
The £800,000 Cold Ash Hill scheme was constructed by civil engineering contractor, Balfour Beatty, with the majority of funding coming from central government and West Berkshire Council together with contributions from Thatcham Town Council and Cold Ash Parish Council.
Pamela Bale, West Berkshire’s executive councillor for Emergency Planning said: “I’m extremely pleased to see this scheme in place. It is an excellent example of the Council’s commitment to building flood defence measures at key locations across the district.”
“Severe weather over recent years has highlighted the key locations. However protection from floods can never be guaranteed, which is why we urge all those living in areas known to have flooded, to do what they can to further protect their own properties.”
This call to ‘help people help themselves’ has developed as a theme across the district. The authorities can do what they can with the money available, and the reservoirs being built above Thatcham are an excellent example of this. But as they continually point out, 100 per cent protection from flooding can never be guaranteed and households should do what they can for their own properties to complement the wider schemes.
To this end, the government has pledged grants of up to £5,000 for homeowners to install measures to help prevent future flooding to their houses. The aim is to see the cash used for installation of devices such as flood guards on doors, self-closing airbricks, non-return valves on waste pipes or for waterproofing or re-pointing external walls. All such measures must be aimed at alleviating the possible impacts of any future flooding to the property. As is to be expected, there is strict government criteria for claiming the cash, but West Berkshire Council is urging all those who may be eligible to apply. Details are on the council’s website website.

Shared determination
On the wider front, the rural reservoir scheme is certainly a major leap forward in the collective effort to combat flooding. Reflecting on the creation of this first attenuation pond Brian Woodham, chairman of the Funding Committee for Thatcham Surface Water Management Plan said: “This is a really significant first step which will enable protection for around two hundred properties in parts of North Thatcham, Southend and Billington Way. It shows what can be achieved even in difficult economic conditions and has been made possible by the dedication of West Berkshire Council’s flood engineers, support from the Environment Agency and Thatcham Flood Forum. We have shared a common financial determination to get this first retention pond in place, our challenge now is to find funding for the next three.”
Richard Benyon MP said: “This is an excellent scheme for Thatcham. I remember the dreadful flooding of seven years ago and continued investment in our flood defences is crucial to ensure that our community does not have to live through a repeat. I pay tribute to all those who have contributed to this scheme.”
Meanwhile, the council is continuing with its flood alleviation programme elsewhere in the district. A bund wall has been created above Shaw, north of Newbury designed to have a similar effect to the Thatcham reservoirs. And with rising groundwater – rather than flash flooding – having been a main contributing factor of floods last winter, the council is working with Thames Water and other agencies to see what can be done regarding drainage and sewer systems. Work is under way from Lambourn in the west, to the village of Aldermaston in the east of the district. For whatever reason, weather patterns appear to be becoming more extreme, and that can only make addressing the issues of potential flooding even more important – in West Berkshire and in numerous other districts across the country, too.

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