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This publication is available at https://www.gov.uk/government/publications/upper-mole-flood-alleviation-scheme/upper-mole-flood-alleviation-scheme
Crawley and Horley are at risk of flooding from the upper reaches of the River Mole, including the Gatwick Stream, Tilgate Stream, Crawters Brook and Ifield Brook. The area suffered from significant flooding in 1947, 1960, 1968, 1974, 1990, 2000 and the winter of 2013 to 2014.
In 2000, 109 homes in Crawley were affected, as was Gatwick Airport. Following this, the Environment Agency began developing the Upper Mole flood alleviation scheme which will reduce the risk of flooding to over 1,400 homes and businesses in Crawley and Horley, and also to Gatwick Airport.
The original scheme consisted of 4 flood storage reservoirs at:
Tilgate Lake, Crawley
This part of the scheme was completed in 2011.
This part of the scheme (by junction 10a of the M23) was substantially complete in 2013. Both Tilgate and Worth Farm helped to reduce the risk of flooding to homes during the flooding of winter 2013 to 2014.
Clay’s Lake, near Balcombe
Construction is due to begin in September 2014.
This part of the scheme has been suspended as significant external contributions would be needed to construct a reservoir at Ifield. The Environment Agency is currently working with partners to identify alternative local measures to reduce the risk of flooding in Ifield.
The scheme also includes work to restore the river to a more natural state at Gratton’s Park. Crawley Borough Council carried out these works in 2013 as part of their contribution to the scheme.
Latest update: June 2014
Following the refusal of the planning application for the Clay’s Lake scheme in December 2012, the Environment Agency submitted a revised planning application to Mid-Sussex District Council, which was approved in January 2014.
A contractor will be appointed in July 2014 and the site will be established from mid-August. These activities will include improving passing places on Parish Lane and creating an access track to the site. Traffic-management measures will be needed on Parish Lane for the duration of the work. These will be discussed with local residents in more detail closer to the start of the work.
The full construction programme is expected to last for 2 years. The Environment Agency expects the work to be substantially complete by summer 2016.
The proposed reservoir in Ifield would require significant external contributions, which are proving difficult to source. The Environment Agency is continuing to work closely with Crawley Borough Council, West Sussex Highways and local residents to develop alternative local measures to reduce the risk of flooding in Ifield.
The Thames Regional Flood and Coastal Committee (RFCC) has given £90,000 of funding to increase the standard of protection to the residents of Ifield Green.
A number of other options to reduce flood risk to homes in Ifield have been identified, such as making changes to road layouts, raising kerbs, adapting the road bridge and works to redirect flow from a field away from properties.
In the coming months these options will be tested using an updated hydraulic model to determine the best possible combination that will offer protection to as many residents as possible.
With the Thames RFCC funding and an offer of match funding of £100,000 each by West Sussex County Council and Crawley Borough Council, the Environment Agency expect to finish the work at Ifield by the end of March 2015.
For more information about the Upper Mole flood alleviation scheme, please contact the project manager, Steve Lee at the Environment Agency on 0118 953 3135 or email: firstname.lastname@example.org.