It’s official: this site constitutes a high-level flooding risk: “The site and its surrounds are within the functional floodplain of the River Wandle (Flood Zone 3b: the highest risk category for flooding). The majority of the site is within a critical drainage area for surface water flooding.” (Merton Borough Council)
The Plough Lane stadium site is regularly subject to flooding, as the images on this page indicate, so any development that fails to address this issue adequately should not be acceptable to local residents or the council. The site (one of the area’s top two highest flood risks along with Colliers Wood) is at risk of flooding from two sources:
- the River Wandle, running close by the site, which is in fact the flood plain for the river. Flood warning for River Wandle
- the ground water, arising from the fact that the site is on a gravel bed.
Any development plans for this site MUST convincingly explain how they will hold within the site all water generated from either source, will not increase flooding on the site above current risk levels and how they will prevent this water from escaping to the surrounding areas. Find out more about how Merton planners must attentuate flood risks in new developments in this report.
How do current plans appear to deal with the flooding issue?
AFC wants to build a large concrete stadium on the site along with 600 homes, substantially increasing the footprint of development here. It is difficult to see how this will reduce flood risks for this site; in fact they are likely to increase. Find out what the experts think…
The greyhound developers intend to build a one-sided stadium and some housing (quantity yet to be announced). Following publication of a consultants’ report on the site, Hume Consulting instructed its architects to cut the amount of housing and residential development on the site by around 50%, in a bid to meet stringent flooding requirements. We have yet to see their revised plans.
Greyhound developers also say that flood water can be allowed to pool on the ground surface within the stadium. The footprint of this development has always been considerably smaller than the AFC Wimbledon plans.
The AFC Wimbledon plans appear to include a large underground holding tank to catch flood water. Unacceptable! This system will merely displace ground water rather than allowing it to dissipate. Imagine you build a swimming pool in your garden: by digging a large lined hole, you are effectively removing the chance for water in that area to drain away, making it more difficult for the rest of your garden to cope with large amounts of rainfall.
The public exhibition on AF Wimbledon/Galliard Homes development proposals referred briefly and vaguely to dealing adequately with flooding issues. No details were provided. We would like to see full technical information on how floodwater will be both contained within the site and allowed to disperse safely and without disruption.
The Greyhound Stadium plan appears to allow water to be held in the centre of the open-roofed stadium and drain away gradually. This would seem to be a more considered approach but of course needs to be thoroughly tested and approved before it can allay local concerns.
What do the experts say? Planning consultants RPS (commissioned by WPRA and Hume Consulting but who have also reported on the site in a study commissioned by Merton Borough Council) conclude that preliminary proposals for the site are weak on flooding and transport grounds. The AFC Wimbledon/Galliard Homes plan in particular is singled out as constituting overdevelopment on a high flood risk site. Read their expert opinion here