Policy paper

Leigh expansion and Hildenborough embankment scheme

Updated 4 November 2025

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Background

Communities in Tonbridge and Hildenborough are at risk of flooding from the River Medway.

Flooding occurred in these areas in:

  • 1960
  • 1963
  • 1968
  • 1974
  • 2001
  • 2013 and 2014

The 1968 event caused significant flooding in Tonbridge and Hildenborough. The Leigh flood storage area (FSA) was built to reduce the risk of future flooding to approximately 1,200 homes and businesses.

It is likely that climate change will increase the risk of flooding in the coming years. The Environment Agency is working on a scheme to increase the capacity of the Leigh FSA. This will help reduce the risk of flooding to more local homes and businesses.

Proposed scheme

The Leigh expansion and Hildenborough embankment scheme will reduce the risk of flooding for more homes in the area.

It has 2 parts:

  • increasing the capacity of the Leigh FSA
  • constructing a new embankment to protect homes in Hildenborough

Currently, we can legally store water to a maximum level of 28.05 metres above ordnance datum (AOD). This is measured at the control structure.

Environment Agency investigations show that storing water to 28.6 metres AOD will reduce flood risk to over 1,800 homes and 575 non-residential properties in Tonbridge and Hildenborough. We will need 16.4 hectares of extra land to store to this level. This will increase the storage capacity by approximately 25% to over 7 million cubic metres.

Doing this needs permission from the Secretary of State for Environment, Food and Rural Affairs to increase the maximum stored water level.

Our application was approved by the Secretary of State in September 2021. This means we can increase the stored water level from 28.05 metres AOD to 28.6 metres AOD.

This approval meant we could start the Leigh expansion and Hildenborough embankment scheme.

Find out more about this decision and the scheme.

Investment and funding

We estimate the scheme will cost £36.14 million. We have secured funding from:

  • government
  • Kent County Council
  • Tonbridge and Malling Borough Council
  • South East Local Enterprise Partnership - which is now the Kent and Medway Economic Partnership

Partnership

The scheme is being delivered in partnership with:

  • Kent County Council
  • Tonbridge and Malling Borough Council
  • Kent and Medway Economic Partnership

Autumn 2025 update

Leigh flood storage area expansion

In spring 2022, the Environment Agency appointed a contractor, VolkerStevin, to carry out the construction works on our behalf.

To expand the flood storage area we are replacing the 3 gates at the Leigh FSA control structure.

We installed the first of the new set of gates in Autumn 2024. Find out more about these works.

The new centre gate for the Leigh FSA control structure was successfully lifted in on 21 May. Find out more about these works.

Over the summer, the first 2 new gates have been successfully connected to the brand-new control system and work has begun to install the final (north) gate. The old gate has been removed and preparations are underway to install the new gate.

The new centre and south gates have been installed at the control structure and the north gate (left hand side of photo) has been removed ready for the new gate to be installed (credit: Robert Mills Photography).

Work to raise sections of the embankment at Leigh pumping station and Cattle Arch bridge near Leigh village are also complete.

The flood storage area remains fully operational throughout the construction works. You can find out more about how the Leigh Flood Storage Area works to reduce flood risk by viewing our animation on YouTube.

Hildenborough embankment

We have designed a scheme that reduces flood risk to as many homes as possible with as little impact on the local community as we can. Tonbridge and Malling Borough Council approved our planning application in November 2022.

The scheme is designed to work with the Leigh flood storage area expansion and will further reduce flood risk to Hildenborough from the River Medway.

It includes:

  • a new embankment
  • pumping station
  • penstock structure on the Hawden Stream

You can find out more about how the Hildenborough aspect of the scheme will work by our animation on Youtube.

Indicative design of the Hildenborough embankment scheme (credit: project team)

Works at Hildenborough have been progressing well, thanks to the good weather. The concrete for the new penstock was completed in the spring. Construction of the new pumping station is progressing well, with the concrete walls now complete. Meanwhile, works within the Hawden Stream are wrapping up, including drainage and riverbank protection works. Work is continuing off-site to manufacture the new pumps and develop the new control system. We expect to install both in the coming months.

Earthworks have also begun with the formation of the new access road and building of the embankment.

New penstock structure on the Hawden Stream which will control the flow of water (credit: project team)

Hildenborough construction site: penstock on the left, pumping station in the centre and base of the new embankment to the right (credit: project team).

Timeline

  • June 2020 – application submitted to Defra to amend the River Medway (Flood Relief) Act 1976
  • April to May 2021 – local enquiry held
  • September 2021 – approval from the Secretary of State
  • November 2022 – Hildenborough planning approval received
  • spring 2022 - contract for construction work awarded
  • autumn 2022 - pre-construction works started at Leigh FSA
  • spring to summer 2023 – construction started at Leigh FSA
  • spring 2024 – construction started at Hildenborough
  • spring 2024 – Leigh FSA control structure gates started
  • autumn 2024 – construct stream crossing for piling works and install sheet pile wall at Hildenborough 
  • winter/spring 2025 - install the new penstock chamber at Hildenborough 
  • summer 2025 – construct embankment at Hildenborough
  • summer/autumn 2025 – install remaining gates at Leigh control structure 
  • autumn 2025 - install new pumping station at Hildenborough
  • end of winter 2025/26 – the scheme will be fully operational

Medway catchment

The Leigh expansion and Hildenborough embankment scheme is part of the Medway Flood Action Plan. The action plan was developed by the Medway Flood Partnership.

It was established in January 2017 and brings together:

  • local partners
  • national agencies
  • non-government organisations
  • community representatives

The partnership focuses on reducing the risk of flooding from non-tidal rivers and surface water in the Medway catchment.

You can find out more on the River Medway Partnership website, and in the Medway Flood Partnership: objectives, members and action plan.

There are 2 other projects in the Medway catchment:

More information

Find out more about the history of the Leigh FSA.

You can ask our project team about the works or join our electronic distribution list for future updates by emailing us.

You can also follow us on Twitter: @envagencyse Hashtag: #LeighFSA; #HildenboroughFAS; #MedwayFAP

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