The Environment Agency is progressing work on the £21.5 million scheme to increase capacity of the Leigh Flood Storage Area (FSA) in the Medway catchment by 24% to over 7 million cubic metres.
The Leigh FSA was built to reduce the risk of future flooding to approximately 1,200 homes and businesses in Tonbridge and Hildenborough at risk of flooding from the River Medway.
Flooding occurred in these areas in 1960, 1963, 1968, 1974, 2001 and 2013/14.
Currently the Environment Agency can legally store water in the existing Leigh FSA to a maximum level of 28.05 metres above ordnance datum (AOD), as measured at the control structure.
Investigations have shown that storing water to 28.6 metres AOD will reduce flood risk to over 1,400 homes in Tonbridge and Hildenborough. Storing to this level will need 16.4 hectares of extra land but will increase the storage capacity by 24% to over 7 million cubic metres.
To reduce the risk of flooding for more homes in the area, the scheme will increase the storage capacity of FSA. Works will also include the construction of an embankment in Hildenborough.
Increasing the maximum stored water level required permission from the Secretary of State for Environment, Food and Rural Affairs, who gave the go-ahead in September 2021, in order for both the Leigh expansion and Hildenborough parts of the scheme to proceed. The application was to increase the maximum allowable stored water level within the Leigh flood storage area (FSA).
The estimated £21.5 million in funding required to build the scheme has now been secured from:
- Government
- Kent County Council
- Tonbridge and Malling Borough Council
- South East Local Enterprise Partnership
While the expansion scheme is being developed, the Environment Agency is investing in a programme of engineering works which will keep the existing FSA fully operational and compliant with the relevant legislation. These works will also feed into the design of the enlargement scheme.
This was increased from 28.05 metres Above Ordnance Datum (AOD) to 28.6 metres AOD. This decision is essential to enable the Leigh expansion and Hildenborough embankment scheme to proceed.
In spring 2022 the Environment Agency appointed contractor VolkerStevin to carry out the construction works on behalf of the Environment Agency.
To expand the FSA and store water at the higher level requires modification of the 3 gates at the Leigh FSA control structure – the work will take place over 3 consecutive summers. This will ensure that the structure can continue to operate over the higher-risk winter periods. The Agency is also planning to raise a section of flood embankment near Leigh village with hard standing for temporary pumps. Pre-construction works are currently programmed to begin at the FSA in autumn/winter 2022. The work at the Leigh control structure gates and the work to raise Leigh FSA embankment near Leigh village will begin in spring/summer 2023.
Tonbridge and Malling Borough Council are currently considering the planning application for the Hildenborough embankment work with construction expected to begin at Hildenborough in 2024. The construction programme at Hildenborough depends on the planning decision.
The full scheme is due for completion in autumn 2025.
The Leigh expansion and Hildenborough embankment scheme is part of the Medway Flood Action Plan developed by the Medway Flood Partnership. Established in January 2017, the Partnership brings together local partners, national agencies, non-government organisations and community representatives. The partnership focuses on reducing the risk of flooding from non-tidal rivers and surface water in the Medway catchment.
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