River Thames Scheme - IEMA Q Mark...آ  The River Thames Scheme (Datchetto Teddington) is one of the

  • View

  • Download

Embed Size (px)

Text of River Thames Scheme - IEMA Q Mark...آ  The River Thames Scheme (Datchetto Teddington) is one of...

  • River Thames Scheme

    Handing over design to the public – did it make a difference?

    24 April 2018

    Jenny Marshall-Evans Environmental Scientist



  • Agenda

    • Introduction

    • RTS Vision

    • Deliberative approach

    • Enhancement opportunities

    • Design areas influenced

    • Engagement shaped the Vision



  • 3

    • 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

  • 4

     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

    surrounding habitats.

    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



  • 5

    Deliberative engagement

    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 ground

    • Pink: landfill

    • Blue: flood embankments


    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.


  • 6 options


    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

    water quality,

    - 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

    sailing club).


  • Option 1 selected








    Strategy (n = 22) 1 (n = 27) 2 (n = 25) 3 (n = 24) 4 (n = 26) 5 (n = 26)







    Actively object

    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 ground

    • Pink: landfill

    • Blue: flood embankments

    Building consensus

    Second example:

    This shows the original strategy alignment - a straight, trapezoidal channel, through

    natural ground.

    Flood embankment to the north to protect the Chertsey water treatment works.


  • 10

    Building consensus

    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.


  • 11

    Abbey Meads







    Abbey Meads

    Strongly support




    Actively object

    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.


  • 12

    Abbey Meads

    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


    Third example:

    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







    Manor Farm Option 1 Manor Farm Option 2

    P e

    rc e

    n ta

    g e

    o f

    v o

    te s

    re ce

    iv e




    support Support


    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