River Thames Scheme
Handing over design to the public –
did it make a difference?
24 April 2018
• RTS Vision
• Deliberative approach
• Enhancement opportunities
• Design areas influenced
• Engagement shaped the Vision
• 14.6 km long
• 20-50 m wide
• 150 m3/s
• 2-3m deep
The River Thames Scheme (Datchet to Teddington) is one of the UKs largest flood risk
management schemes of recent years. It involves construction of a 15km long flood
relief channel through west London. Black & Veatch is leading outline design for the
Environment Agency and partners.
The new flood channel is in 3 sections (red dashed lines).
• Nearly 15km in length and
• Up to 50m wide
• Flow capacity of 150m3/s
• 2-3 m deep, but water level increases by c.1m when channel in operation
New opportunities for tourism/recreation/sport
Improving access to the river
Improving landscape and habitats
The vision consists of 3 elements:
- Protecting the communities in the area by reducing flood risk
- Securing the economy by keeping businesses and transport running, allowing the
communities to thrive and encouraging investment
It is the last item where our vision goes beyond the “functional” and becomes more
- To enhance the area by providing new opportunities for tourism, recreation and
sport; improving access to the River Thames; and improving the landscape and
In response to this vision, the project team has placed strong focus on the landscape
and environmental design. Of course, the design has to function as a flood scheme, but
to deliver these wider benefits the scheme needed to be ambitious in its aspirations,
and ensure landscape and environment were at the centre and fully integrated into the
design. It was with these aspirations in mind that we sought to engage the public in the
A deliberative approach was adopted to engage with the wide variety of
stakeholders, including authorities, user groups, conservation bodies and
The Discussion Groups help stakeholders to work through the complexities of the
channel design. The key objectives are to give participants an opportunity to:
• share their views, knowledge and expertise,
• suggest ideas; and
• explore options about what the channel could look like and how it can be
used; whilst also
• ensuring that it creates benefits for people, livelihoods and nature.
By using this approach, we hoped to maximise the potential for the Project to
deliver mutually acceptable designs that bring multifunctional benefits, attract
partnership and investment funding, and empower community groups,
organisations and businesses to be stewards of the improvements it will deliver.
Incorporated stakeholders in the iterative design process, including consideration
of the potential environmental effects.
- Minimising the projects environmental impact and enhancing the benefits, as
part of the EIA process.
• Green: natural
• Pink: landfill
• Blue: flood
Channel section 1
We identified an area where we felt there was a better route to that agreed in the
original Strategy, and wanted the discussion group to be a part of the option appraisal
On this drawing, there is a long section of channel through landfill (as shown in the
pink), and our ground investigations showed this to be a particularly nasty site, with
medical waste found. We therefore considered some alternatives.
Influencing the design
Optional appraisal using multi-criteria evaluation
Feedback from Discussion Groups
Consensus building at final Discussion Group Workshops
- potential effect the introduction of River Thames water would have on the lakes
- the risk of introducing invasive species and
- the affects the different options would have on recreation in the lake (especially as
the northern lake is currently a commercial fishery and the southern is used by a
Strategy (n = 22) 1 (n = 27) 2 (n = 25) 3 (n = 24) 4 (n = 26) 5 (n = 26)
There was strong opposition to the Strategy option through the landfill and also for
options 2 and 3 which had the greatest impact on recreation in the lake. The most
favoured options (or the least opposed) were options 1 and 4.
We later undertook groundwater and water quality modelling to assess the impact on
water quality, and using this were able to demonstrate to Natural England (needed
because the lake is part of the South West London Water Bodies Special Protection
Area) that it was not necessary to isolate the flood water from the River Thames from
the rest of the lakes, so separation embankments were not required.
A consensus was reached.
• Green: natural
• Pink: landfill
• Blue: flood
This shows the original strategy alignment - a straight, trapezoidal channel, through
Flood embankment to the north to protect the Chertsey water treatment works.
The first workshop asked for ideas for enhancements from stakeholders, including areas
of habitat creation, footpaths, viewpoints etc…
Using the stakeholder idea for habitat creation in this area we subsequently developed
our habitats strategy and led us to focus our efforts on specific locations, such as the
channel at Abbey Meads.
In consultation with Affinity Water identified the need for a shallow, wider channel in
this area to prevent affecting their groundwater abstraction requirements.
Having developed a habitats concept using the views from the first workshop the
proposed concept was presented to stakeholders at the second workshop.
No one actively objected to design and overall the majority supported it
We were able to build consensus on this section of the channel.
Using the ideas provided from the discussion groups, expertise from the Project Team
and engagement with the water utility company we were able to develop a concept for
this area of the channel that met the needs and aspirations of all stakeholders and
contributed to achieving all elements of the RTS vision.
We have further developed the design, due to the consensus built from the discussion
groups and have created an area of high value habitat enhancements, incorporating the
entire area in to the channel to create a wet meadow that will be partially flooded in
winter and largely dry in summer with rough grazing during the summer months.
Shaping the Vision
On this drawing there is an existing landfill site – it’s been poorly restored - and has a
degraded landscape. The project, by its nature of excavating a flood channel, generates
an excess of freely available material (approximately 1.5 million cubic meters).
An initial concept for a raised landform was sketched then a more detailed drawing of 2
options presented to the discussion groups:
- option 1 was the development of country park
- Option 2 was a sports and activities recreation center
Option 1 selected
Manor Farm Option 1 Manor Farm Option 2
The Discussion Group Workshop preferred the concept proposals for option 1.
Stakeholders had several concerns with option 2, with 47% expressing concerns and only
6% expressing support for the ‘Active Leisure & Development’ concept. Option 1 was
subsequently taken forwards as the chosen configuration for the LEA. In certain
instances, specific comments from the Discus