Thames Water

Ashley Book and Nishad Sowky from Thames Water and Tom Sly from Merton Council gave a presentation on local flooding issues. The presentation is attached to this report. Nishad and Tom explained that responsibility for infrastructure above ground is Merton Council’s but below ground it is Thames Water’s. In Raynes Park there is separate foul water and surface water. Raynes Park town centre is low, with a raised embankment and river catchment areas.

Current work includes:

·         Worple Road – carrying out an investigation

·         Abbotts Avenue – still looking to reduce the risk of flooding

·         Cottenham Park – tackling a build-up in the sewers

·         Coombe Lane – trying to resolve blockages

·         Seaforth Road – carrying out surveys and investigations.

In addition Merton Council is investigating surface water across the whole of West Merton (Raynes Park and Wimbledon). We have also undertaken extensive gully cleaning programme, with 10,500 cleaned and another 9,000 to be cleaned this autumn. Gully sensors have been installed to monitor silt levels and surface water.

Gathering data has allowed to build up a picture that will inform future strategy, a Drain Water Management Plan. This can be brought back to a future meeting.

It is crucial that residents report flooding when it happens, Merton gets lots of reports, Thames Water not as many. Reporting helps us to build a business case and can include a sewer flooding questionnaire.

Tom explained that under the planning process he is consulted on all major and minor applications and has been able to influence development to help slow the flow of water through Sustainable Drainage Systems (SUDS) and improving green infrastructure. Thames Water are not statutory consultees but do support measures to reduce flow.

Jane Barnes from the Residents Association of West Wimbledon (RAWW) said that the extent of flooding in the area was greater than many realised and gave a number of recent examples. Tom agreed that the issue seemed to be misconnections between the surface and foul water networks. Slowing the flow is critical to helping the network cope. Storm Francis was a high intensity rainfall event that overwhelmed the network. These should be rare events, but with climate emergency these storms could be more likely. As a result we will focus on keeping the foul and surface water separate.

At a previous meeting Thames Water said they had cleared a blockage at Crescent Road. Nishad confirmed that they had checked and found the blockage was still cleared.

A resident asked about off street parking and Tom replied that this can be a problem. Any space over 5m² needs planning permission and must be permeable. Abbott Avenue residents had been given a code to use when reporting to Thames Water and Ashley agreed to looking into whether other residents could receive a code.

Tony Edwards from the RPA asked about gully clearance. Tom explained that Conway are contracted to provide two clearances a year as part of the highways contract in high risk areas. Veolia are contracted to do additional reactive clearing.

A resident raised the Lost Effra project in Lambeth following the historic channel of a river, adding greening measures along the catchment. Merton would support following a similar model and has some funding from the Neighbourhood CIL to conduct clearing of eight high-risk culverts.