EXECUTIVE SUMMARY

MAIN REPORT

1.                  BACKGROUND

1.1              The Environment Agency (EA) has prepared a draft strategy to tackle flood risk in the Lower Thames (Datchet to Teddington).  It is called the Lower Thames Flood Risk Management Strategy (LTFRMS).  It has been published for public consultation with a closing date of 4 December 2009 – however Spelthorne has been allowed more time to enable Cabinet’s consideration of this report. The EA has held two public exhibitions in Spelthorne.

1.2              Its aim is to reduce the risk of flooding to more than 15,000 homes and businesses standing within the floodplain.  Over 2,000 of these homes are in Spelthorne where significant areas of the Borough are at risk.

1.3              In 2000 and 2003, floods resulted in a number of homes in Spelthorne being flooded, particularly in the areas of Wheatsheaf Lane and Chertsey Bridge.  These underline the scale of the damage and disruption that can be caused.

1.4              The EA has been considering possible alleviation measures for many years but this work has been progressed significantly since 2003.

1.5              For some while, the EA have made it clear that a comprehensive approach was needed involving a package of measures.  A key element of this has been a concept of three separate flood relief channels.  The possibility of such an approach is recorded within the text of the Council’s recently adopted Core Strategy and Policies Development Plan Document (CS PDPD).  Policy LO1 – Flooding – gives specific support as follows:-
“supporting appropriate comprehensive flood risk management measures within or affecting the Borough which are agreed by the Environment Agency.”

1.6              There are inevitably constraints to what can be achieved and the proposal being put forward cannot eliminate all flood risk.  The major constraints are topography, extent of the built up area and other environmental issues. In financial terms any scheme has to achieve an appropriate level of benefit over cost.

1.7              The strategy involves:

a)     Construction of the flood relief channels in Reach 3 (Datchet to Walton Bridge) of 50 to 60 metres wide (see colour plans in Appendix 1):
i)    Channel 1 - north of Staines from Datchet to South of Wraysbury (North           bank of Thames).  This will help relieve Datchet, Wraysbury and Egham.
ii)   Channel 2 - South of Staines on the Runnymede side from a point        opposite Wheatsheaf Lane to Chertsey Lock.  This will help relieve South
      Staines and Chertsey.
iii)  Channel 3 - Chertsey Lock to Shepperton on the Spelthorne side of the           river.
      This ‘channel’ will benefit Chertsey and Shepperton and will have two  elements:
                  - main channel from north of the M3 bridge via Littleton Lake
                    then running parallel to Sheep Walk via Ferris Lake and south of
                    Shepperton Square
                  - minor channel from south of M3 bridge and passing under
                    Chertsey Bridge Road east of Dumsey Meadow.

b)     Capacity improvements in Reach 4 (Shepperton to Teddington) will help relieve Shepperton, Sunbury and other settlements and urban areas outside the Borough by:
i)    widening the Desborough Channel on its south side by 3-4 metres (not in
      Spelthorne).
ii)   increasing the capacity of Sunbury, Molesey and Teddington Weirs.

c)      Flood plain management will provide general benefits through out the strategy area including:
i)    increasing the public awareness of flooding.
ii)   working through the planning process to restrict development in flood risk
       areas.
iii)  safeguarding flood flow routes – these generally coincide with diversion
      channels.
iv)  very localised community based flood prevention measures where
      appropriate.
v)   effective community evacuation plans.
vi)  use of Thames Barrier when possible to retain capacity in the tidal
      Thames for as much flood flow as is possible.

1.8              The intention is that the new flood channels would be designed in such a way to fit into the character of the landscape, protect/enhance biodiversity and secure improvements where possible. They would provide the opportunity to create new footpath/cycle routes alongside with links into the existing routes.  New water areas could be used for fishing, wildlife and small boats but use for general navigation would require additional locks, and though identified in the consultation material is not a specific proposal.

1.9              The new channels would cost in the order of £200m and the package as a whole is estimated at £300m.  The EA hope that, subject to adoption of the Strategy, the flood plain management elements (not involving major construction) could be implemented from 2011.  The flood channels would not only need to secure funding but require detailed designs and planning approval.  They would not be started until 2017.  No completion date is offered at this stage.  The scheme funding depends on Defra and the Treasury.

1.10         No detailed design work has been undertaken only general routes for channels have been shown.  These have, nevertheless, been subject to a Strategic Environmental Assessment with a 250 page report.  In due course a detailed scheme would need an Environmental Impact Assessment.  Comments at this stage need to focus on the key issues.

1.11         The EA’s assessment is that in Reach 3 from Datchet to Walton Bridge, where the majority of properties in the flood plain are, flood risk could be reduced significantly by the proposals:

1.12         In Reach 4, 540 households would be lifted from the ‘Very Significant’ and ‘Significant Risk’ category into the ‘Moderate’ category.

 

2.                  KEY ISSUES

2.1              The Council is already committed to an appropriate comprehensive approach to flood risk management.  The issues for the Council to consider are:

a)     Whether the measures proposed are appropriate to deal with flood risk in Spelthorne.

b)     If there are further/alternative measures.

c)      Any detailed comments on the draft strategy as proposed.

 

3.                  OPTIONS ANALYSIS

3.1              The EA have considered options to their proposals or possible additions to them.  The options and reasons for their rejection are:

a)     Do minimum by just maintaining things as they are – rejected because it would leave thousands of people at flood risk.

b)     Deepening the river – rejected because of environmental damage and long term cost of maintaining the new profile and disposal of material.  On its own the resultant increase in channel capacity is small.

c)      Raising banks and defences – will be used on a limited basis but if used generally would increase flood risk by not allowing the flood plain behind such structures to drain naturally.

d)     Flood storage – rejected because this would require an area upstream to be equivalent to the size of half of Oxfordshire.

e)     Alternative channel routes – various options were considered but rejected on the grounds of environmental impact or efficiency relative to benefits.  Due to the existing extent of urban development no acceptable channel system below Walton Bridge could be selected and neither could a channel to by-pass Staines town centre be identified.

4.                  PROPOSALS

4.1              To put the scale of the flood risk and additional water capacity into context, the Thames at ‘bank-full’ has a capacity of 250 cubic metres of water per second (cumecs).  In a 1 in 100 year flood event, this would be around 600 cumecs.  An ‘appropriate’ strategy therefore needs to deliver significant additional capacity throughout the river length at risk.

4.2              The EAs proposals have been subject to extensive study and consultation in their formulation and provide an appropriate comprehensive approach which can deliver a significant reduction in risk. 

4.3              The diversion channels are inevitably significant in scale but offer scope for enhancement of some of the areas through which they pass where past mineral workings have been poorly restored.  There is scope for benefits in associated improved public rights of way and associated recreational benefits.

4.4              Success of the scheme in terms of environmental impact will, however, be dependent on getting precise alignments and the detailed design right.  A detailed scheme would require planning permission and be subject to further prior consultation.

4.5              Only one of the diversion channels (Channel 3) is in Spelthorne as well as only one of the locks (Sunbury) proposed for improvement.  The supporting documents explain that Channel 3 would have to be completed before proceeding to No. 2 and then No. 1.  The sequence is necessary to otherwise avoid temporarily increasing flood risk downstream of improvement works.

4.6              The scheme as a whole does raise some issues which will need careful resolution at the detailed design stage.  These are not recommended as matters of objection to the principle components of the strategy but matters which it is suggested the EA are asked to give particular attention to.

1.      Channel 2 may pass close/through the edge of the Thorpe Hay Meadow SSSI in Runnymede.  As a matter of principle the loss of any part of an SSSI should be avoided.

2.      Channel 3 passes through a plot of land adjacent to the Dumsey Meadow SSSI which was purchased by the Chertsey and Shepperton Regatta for car parking during the annual regatta.  It is unclear whether a channel could be constructed through this site without also requiring part of Dumsey Meadow for construction related work and also where alternative parking would be provided.  Parking on Dumsey Meadow would further damage the SSSI which is already subject to a management plan to bring it up to the standard it should be in.

3.      The new channels will require roads to be raised over them with resulting relatively long structures.  These need to be carefully designed to avoid adverse impact on access to property as well as adverse visual impact.

4.      There is some lack of clarity over the implication for the section of river through Staines which will have no by-pass channel and whether any benefits will be secured. The Council will want assurances that the scheme will also include flood relief benefits to the gap between the proposed Channels 1 and 2.

5.      The channels pass through areas designated as part of the South West London Water Bodies Special Protection Area (SPA) as well as non-designated areas nevertheless having a significant role as feeding areas, eg, Shepperton Ranges.  The detailed scheme will need to not only minimise such impact but ensure adequate compensation areas are provided.

6.      The Strategic Environmental Assessment has not identified the cumulative adverse impacts on SSSIs when taken with the Airtrack proposals – this is a requirement of the SEA process.

7.      Suggested opportunity to use Ferris Lake (Ferry Lane, Shepperton) to create a marina conflicts with its use in supporting the SPA. There would also be adverse impact on the openness of this site which is in the Green Belt. The Council would not support a marina.

8.      Possible use of channels for navigation by larger craft would conflict with potential wildlife benefits.

9.      Reference on page vii of the Summary of the SEA to reducing development next to the river through planning policy - this needs clarifying as it is not included as part of the Strategy and in any case was assessed in the Council’s Strategic Flood Risk Assessment as prohibitively expensive.

 

5.                  BENEFITS AND SUSTAINABILITY

5.1              The intention of the scheme is to deliver significant flood relief benefits in a sustainable manner.  Subject to the points raised in para 4.6 above, the strategy has the scope to achieve this.

6.                  FINANCIAL IMPLICATIONS

6.1              There are no financial implications for this Authority that are so far identified.  It will not be responsible for the scheme’s implementation or funding and no Council land is directly affected.  It is unclear how it might affect the costs of the Council’s emergency planning function in the longer term.

7.                  LEGAL IMPLICATIONS / OTHER CONSIDERATIONS

7.1              There are none at this stage.

8.                  RISKS AND HOW THEY WILL BE MITIGATED

8.1              The greatest risk to residents and businesses is through not addressing the existing extent of flood risk.  The Strategy proposes an appropriate and comprehensive approach to dealing with this.

9.                  TIMETABLE FOR IMPLEMENTATION

9.1              This is covered in paragraph 1.9 above.

Report Author: John Brooks, Deputy Head of Planning and Housing Strategy.

Background Papers: (Copies of the papers referred to in this report are available in the Members’ Room)