Policy paper

Slough flood alleviation scheme

Updated 28 August 2015

Background

Communities in Slough have a history of river, surface water, sewer and groundwater flooding, with flood events experienced as recently as 2007, 2009, 2012 and 2014.

Within the catchments of the Chalvey Ditch, Salt Hill Stream and Datchet Common Brook over 1,800 properties are at risk of river flooding and a further 1,000 properties are at risk of surface water flooding, which is caused by rainfall overwhelming local drainage systems.

Reducing flood risk in Slough

The Environment Agency and Slough Borough Council are working in partnership to investigate whether the potential options (see below) to reduce the risk of river and surface water flooding within the catchments of the Chalvey Ditch, Salt Hill Stream and Datchet Common Brook are technically and economically viable.

The results of these investigations will be considered alongside feedback from the local community. If this work identifies that there are viable options, then the Environment Agency and Slough Borough Council will develop a business case for the project. If this is approved a detailed design of the scheme will be developed, followed by construction.

Have your say about how we reduce the risk of flooding

The potential options to reduce the risk of both river and surface water flooding are shown in the table and maps below.

If you have any thoughts or comments about these proposed options then please let us know by emailing enquiries@environment-agency.gov.uk or calling 03708 506 506 by 2 October 2015.

These comments will be considered as part of the Environment Agency and Slough Borough Council investigations to help decide the preferred option for the scheme.

Watercourse	Option number	Description
All	O7	Use sustainable urban drainage techniques: measures such as attenuation tanks, oversized pipes, water butts, and soakaways.
All	CH11, SH12, DC7	Provide individual property protection (IPP) to properties at risk of flooding: IPP measures include door barriers and air-brick covers to reduce the risk of flooding to individual properties.
Chalvey Ditch	CH3	Cippenham Village Green flood storage area: create an earth embankment and re-route stream to create a storage area (the existing channel will be left as an overflow channel). Investigate any potential restrictions of flow, such as the footbridges.
Chalvey Ditch	CH5	Improve the operation of ponds and weirs: redesign weirs, or install adjustable weirs to improve flow and maximise flood storage. Investigate the feasibility of replacing the existing sandbag structure (which holds back flows in the pond) with gabion baskets. This option includes the upper and lower ponds.
Chalvey Ditch	CH10b	Increase storage capacity of Haymills reservoir: excavate reservoir to create a larger volume for storing flood water.
Chalvey Ditch	CH15	Improve drainage from Iona Crescent to Chalvey Ditch: build a drain from Iona Crescent to Chalvey Ditch.
Chalvey Ditch	CH16	Improve surface water drainage at IONA industrial estate: install features such as green roofs and permeable paving.
Salt Hill Stream	SH1	Park Road flood storage area: build earth embankments or use the elevated Park Road to create storage within the wooded area.
Salt Hill Stream	SH2b	Stoke Park golf course flood storage area: build an earth embankment across the southern boundary of the golf course, with an in-channel flow restriction to create a flood storage area within the wooded area on the west bank of the stream.
Salt Hill Stream	SH4	Granville Road recreation area flood storage area: reduce the channel size, narrow the entrance to the stream culvert and build an earth embankment to create a storage area. Land levels could also be lowered to create additional storage. There is also the potential to improve the channel by creating a low-flow channel and wetland area.
Salt Hill Stream	SH5	Godolphin Park and Baylis Park flood storage area: create a flood storage area, improve a small section of the channel in the central part of the park between Godolphin and Baylis Park. Remove the culvert along the pathway to the north of Godolphin Park.
Salt Hill Stream	SH6	Salt Hill Park flood storage area: create a flood storage area by building an earth embankment at the southern end of Salt Hill Park. There is also the potential to lower land in this area to provide further storage. The former location of Salt Hill Pleasure Grounds could also be deculverted and a small flood storage area built. Improvement works may be carried out to the bed of the river and in-channel habitats for fish.
Salt Hill Stream	SH7	Montem Lane flood storage area: narrow the river at the existing culvert at the southern end of the site and build an earth embankment to create a flood storage area.
Salt Hill Stream	SH9	Improve existing trash screens: many of the trash screens need to be cleared during flooding to prevent blockages. Improving or replacing them would reduce the risk of blockages and reduce the need to maintain them. Specific locations include trash screens at Penn Road, Stoke Park Golf Club, Granville Playing Field, Godolphin Park, Salt Hill Pleasure Gardens and Church Street.
Salt Hill Stream	SH10	Build raised defences along the watercourse at Newbery Way and Church Street.
Salt Hill Stream	O1	Transfer water between the two tributary channels on Salt Hill Stream: create a channel to move flood water from Stoke golf course to The Lanes golf course.
Salt Hill Stream	SH17	Improve the existing culvert entrance and construction of a flood wall: this will prevent high water levels flooding onto the road.
Datchet Common Brook	DCa	Increase flood storage at Wexham Park Hospital eastern pond: raise low spots around the pond to increase the volume of storage. Extend the flood storage area into the agricultural field upstream. Replace the existing inlet structure to reduce the risk of blockage and replace the outlet control structure.
Datchet Common Brook	DC4	Flood storage area to east of Grangewood (on the Grangewood Diversion Channel): Datchet Common Brook splits at Grangewood with part of the flow passing through a culvert under Grangewood and the other part routed around the residential area to the east. This option would limit the flow through the culvert and allow more water to pass through this diversion channel. An earth embankment would also be built to create a flood storage area.
Datchet Common Brook	DC8	Flood storage area to the north of Church Lane: create a formal flood storage area where modelling predicts flooding would occur.
Datchet Common Brook	DC9	Increase flood storage at Upton Lake Reservoir.

Chalvey Ditch potential options map.

Salt Hill Stream potential options map.

Datchet Common Brook potential options map.

Next steps

In late August and early September a newsletter about the scheme will be sent to the local community. This will explain how they can provide the Environment Agency and Slough Borough Council with thoughts and comments about the proposed options.

In autumn 2015 the Environment Agency and Slough Borough Council plan to hold public drop-in sessions. These will give the local community the opportunity to review, discuss and provide feedback on the preferred option. This feedback will be used to develop the business case for the scheme and, if this is approved, in the detailed design. The detailed design of the scheme would be developed during 2016 with construction potentially beginning in 2017.

The benefits of the scheme

As the scheme has not been approved or designed, it is not clear yet how many properties would benefit. However the scheme could significantly reduce flood risk from the Salt Hill Stream and Datchet Common Brook and may improve existing flood protection from the Chalvey Ditch.

The scheme may also improve local biodiversity and enhance recreational facilities in the community.

Funding the scheme

If approved, the estimated cost to design and construct the scheme could be over £3 million. However this provisional figure will be reassessed as the project develops.

Slough Borough Council, the government and the Thames Regional Flood and Coastal Committee have committed funding to the scheme based on the estimated cost. The Environment Agency and Slough Borough Council will continue to find other sources of partnership funding.

Working with the community

The Environment Agency and Slough Borough Council have been working to raise awareness of flood risk and have helped to set up community flood groups.

As part of the next phase of the project community groups, local residents, businesses and environmental groups will have the opportunity to comment and input towards the design of the scheme.

The Slough Flood Alleviation Scheme presents a real opportunity to reduce flood risk and reconnect local people with their rivers. The Environment Agency and Slough Borough Council are working hard to listen to the needs of local stakeholders to ensure their views are heard.

Contact

For more information, email: enquiries@environment-agency.gov.uk.