Some of these homes and businesses are more at risk of flooding than others (i.e. they face a much greater than 1% annual risk). Climate change may bring warmer, wetter winters, further increasing the risk of flooding in the future.
The most significant flooding in living memory was in February 1947, but the Lower Thames has already experienced two significant floods this century, in 2000 and 2003. The most recent brought flooding to many areas of the River Thames downstream of Datchet.
Since then, we have been planning a way to manage flood risk from Datchet to Teddington. The Lower Thames Strategy is the result of this work and sets out our preferred approach for managing the risk of flooding in the future. The draft strategy is subject to central government approval, funding and planning permission.
A combined approach
Our approach is divided into two main components: an engineered component and the
floodplain management component.
Engineered component
The engineering component comprises three flood diversion channels:
• Channel 1 would run from Datchet to Wraysbury;
• Channel 2 would run from Egham to Chertsey;
• Channel 3 would run from Chertsey to Shepperton.
In advance of the channel construction, we propose structural improvements to Teddington, Molesey and Sunbury weirs. We would replace a 30m wide section of the existing weir structures with much deeper gates to enhance the flow capacity of the whole weir complex. We are also proposing widening the Desborough Cut channel to accept greater volumes of water.
Floodplain management component
This component would focus on managing the floodplain and would consist of:
• Development control and flood management
We would work more closely with local authorities to ensure that future development takes flood risk into account and safeguards routes for flood flow and the potential routes of the diversion channels. To help us with this, we have developed and piloted specialist floodplain management software that would enable land use planners, development control and emergency planners to visualise flood risk.
We would improve public awareness of flood risk and work with communities to encourage those at risk to sign up to our Floodline Warnings Direct service: a free service that provides flood warnings via telephone, mobile, email and SMS text messages.
• Community-based measures
We would work in partnership with local authorities and other public bodies to develop emergency plans, local flood action plans, community-based protection measures and apply the best means available to make individual properties resistant to floods (including community-scale temporary and demountable defences and individual property protection).
The benefits
The overall benefits of our proposed approach are summarised as follows:
Homes and businesses
• Flood risk to 5,100 residential properties (housing about 12,800 people) and approximately 450 commercial properties would be significantly reduced;
• Approximately 7,200 residential properties (about 18,000 people) would be taken out of 1 in 100 year flood risk (their flood risk would be reduced to less than 1 per cent annual chance of occurrence);
• Flood levels in the River Thames, and therefore in tributary and adjacent drainage channels, would be lowered;
• The floodplain management component would incorporate surface water issues as a central element, using modelling tools to predict surface water flooding.
Infrastructure
There are numerous utility assets and facilities located in the study area, currently at a 1 in 15 year to 1 in 50 year risk. These would have their flood risks reduced to between a 1 in 50 year and 1 in 200 years.
Environment
In the long term there would be improvements to the local landscape character and biodiversity, creating an overall enhancement to the local environment.
The impacts
The overall impacts of the strategic approach proposed for the Lower Thames are summarised as follows:
• The most significant impacts to people and environment would be during the construction of the new diversion channels. These would involve major civil engineering works, affecting the boroughs of Windsor & Maidenhead, Runnymede and Spelthorne;
• During the construction of the channels, it is likely that there will be an impact on the fish population and there may be a temporary change in water quality.
• Most of the impacts on the local landscape would be short term. In the long-term, new planting would help to integrate the channels into the landscape, creating an overall enhancement.
More information about the potential impacts are in the consultation document on page 19. We would ensure that these impacts are kept to a minimum.
What happens next
Funding and delivery
This draft strategy will need funding approval for the whole life (capital and maintenance) costs. The value of this application is likely to be in excess of £300 million and therefore will need to be submitted to Defra and the Treasury for approval. Our proposed options would be delivered through separate projects. Each project would require individual approval through either Environment Agency or Defra processes, depending on the scale of works. The projects would be delivered in a phased manner based upon the funding availability and priority scoring (derived through benefit against cost, number of households benefiting, and environmental enhancement). If any of the projects do not achieve a suitable high priority score and funding is not available then there is a risk that some parts of the project may not be constructed.
Timescales for delivery
Due to the potential scale of the capital works, it is likely that it would take several years for the detailed design, the necessary planning approvals, and construction of any of the channels. Therefore, we are planning a floodplain management approach if and until the bypass channels are constructed.
The floodplain management component of the draft strategy would be carried out between 2011 and 2014, subject to approval.
Consultation on the strategy
We have consulted with many statutory and non-statutory stakeholders during the development of the draft strategy. These include: Natural England, English Heritage, RSPB, BAA, Local Planning Authorities, landowners, utility companies and the Crown Estate. As we move towards the next stage of the draft strategy, we will be talking to the general public.
The public consultation for the Lower Thames Strategy will begin on Monday 21 September 2009 and close on Friday 4 December 2009. We will be holding exhibitions for the general public in the strategy study area.
For more information about the strategy, including detailed information about the diversion channels, please visit www.environment-agency.gov.uk/lts.
We would like to know your views on our draft strategy. To have your say please visit the online consultation document at www.environment-agency.gov.uk/lts.
Have your say about our plans to reduce flood risk.
Currently 15,000 residential properties within the Lower Thames floodplain from Datchet to Teddington are at a 1% risk of flooding in any one year. Our recommendations include building flood diversion channels, improving river weir structures, providing some localised protection for groups of houses and a range of other ways of managing the floodplain.
You can find out more about the draft Lower Thames Flood Risk Management Strategy by attending one of our public exhibitions.
We will be on hand to answer your questions and discuss the recommendations. Your comments will help finalise the strategy. All exhibitions are open between 3pm and 8pm except at Mole Hall, Molesey which is open between 3pm and 7.30pm.
Public exhibitions –
Thursday 1 October Staines Community Centre Thames Street, Staines TW18 4EA
Tuesday 6 October Mole Hall, Molesey Bishop Fox Way, West Molesey KT8 2JE
Thursday 8 October Hythe Centre Thorpe Road, Staines TW18 3HF
Tuesday 13 October St Mary’s Hall Teddington Langham Road, Teddington TW11 9HF
Tuesday 20 October Kingston Grammar School (Theatre) London Road, Kingston upon Thames KT2 6PY
Tuesday 27 October Wraysbury Village Hall The Green, Wraysbury TW19 5NA
