Who are we?

The Purley Flood Defence Group was established in early 2014 as part of a comprehensive initiative, involving local residents, to protect as many properties as possible in Purley that are vulnerable to flooding.

The Group works alongside the excellent Flood Warden emergency response group led by Bernard Nix, however it forms a separate entity, focused on the establishment of future flood defences, with no responsibility for individual flood events, property-level flood protection etc.

PFDG is run by a steering group consisting of the following people:

  • Fiona Williamson (Chair) (Mapledurham Drive)
  • David Jones (Treasurer) (Wintringham Way)
  • Tracey West (Secretary) (Mapledurham Drive)
  • Mel Stevenson (Communications) (Chestnut Grove)
  • Tim Metcalfe (West Berkshire District Councillor) (Home Farm)
  • Bernard Nix (Purley Parish Councillor) (Wintringham Way)
  • Stuart Chester (River Gardens)
  • Jim Lemin (Colyton Way)
  • Steve Young (Wintringham Way)

This is an inclusive, Purley-owned initiative - local residents working together with flood and water experts, using our skills, local knowledge and experience to help the community in our bid to take as much of Purley out of the flood plain as we can.

We are always on the lookout for assistance and expertise.  If you would like to help, please get in touch – here.  We’d be delighted to hear from you.

Aims & Objectives
  1. To represent the community in working towards a comprehensive set of flood defence measures that will achieve protection for as many properties as possible in the vulnerable area of the village.
  2. To build and maintain effective relationships with other organisations to assist with achieving the above. These include the Environment Agency, Local Authority, Thames Water, The National Flood Forum and other community flood groups.
  3. To work towards ensuring that the village infrastructure, such as sewers, electricity, telecommunications etc, are flood resilient and therefore minimising the impact of flood events to the community.
How Purley floods

Groundwater

Groundwater flooding occurs when the water table rises due to prolonged heavy rainfall.

Higher rainfall means more water will infiltrate into the ground and cause the water table to rise above normal levels. Groundwater tends to flow from areas where the ground level is high, to areas where the ground level is low. In low-lying areas the water table is usually at shallower depths anyway, but during very wet periods, with all the additional groundwater flowing towards these areas, the water table can rise up to the surface causing groundwater flooding.

Groundwater flooding is most likely to occur in low-lying areas with permeable rocks (aquifers) below.  In the case of Purley on Thames, the gravel and sandstone that underlies the ground in the lower parts of the village is highly permeable, so when rainwater cannot run off into the river or drains any more, many houses in lower Purley experience water rising in their gardens, up to waist-level in some cases.  Groundwater flooding takes longer to dissipate because groundwater moves much more slowly than surface water and will take time to flow away underground.

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River water

Riverwater flooding occurs when a river cannot cope with the amount of water draining into it from the surrounding land.  This causes it to overtop its banks, and the overspill water runs into adjacent fields, gardens and other land.  Residents of lower Purley will know that historically, water enters Wintringham Way from across the adjacent fields in the gaps between the houses and enters River Gardens and lower Wintringham Way/Chestnut Grove by travelling up the river end of Wintringham Way.  It remains to be seen how this behaviour will differ now the bund is in place.  At the very least, the speed with which the water flows into this area should be significantly reduced.

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Calleys Alley fills with water and often becomes inaccessible and, during severe flooding, dangerous as flood water flowing in through Wintringham Way flows along Chestnut Grove and back down to the river via this alleyway, and the current becomes very strong. 

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The Causeway at the end of Mapledurham Drive, originally put in by the EA to facilitate their access to the Lock, acts like a dam when the river first starts to overtop its banks.  The result of this is that water flows coming across the fields above the lock are arrested and pushed further inland towards and past Bucknells Meadow and the playground, towards the southern end of Mapledurham Drive.  Since the Causeway has a high point of 39.2m and the southern end of Mapledurham Drive is at 38.8m, properties on this road have, in recent years, been flooded with surface water levels from above the lock.  This dam-like effect means that, when the Causeway is finally overtopped, this property-level flooding results in a significant amount of water entering properties in a matter of a few hours. 

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PFDG are currently in discussions with the EA about the possibility of creating gullies/culverts under the Causeway, which will hopefully allow the water to continue its more natural journey down the fields parallel with the river, and thereby affecting fewer houses in lower Purley. 

Sewage

St Marys Avenue floods with sewage running down the pipes from upper Purley.   This is caused by floodwater overwhelming the drainage system, forcing the sewage to re-route.

What does this mean and can we do anything about it?

Groundwater flooding, for residents near to the river, is a fact of life.  Due to the permeable layers of ground under the houses, this area is almost an extension of the river and no flood defences can prevent water seeping up into gardens when the water table reaches a certain height.

Riverwater flooding, however, is something that flood defences can offer some protection against.  By building strategic defences around lower Purley, at the very least, the sheer force and speed at which the water rushes into the streets can be reduced, and in some cases, water can be prevented from entering certain roads altogether, held back instead in the fields by bunds and other flood defence systems.