Hardmead Sluice Replacement Project Information Page

Closes 1 Jul 2024

Opened 25 Jun 2021


Last updated on 14 March 2023

We are going to replace the one current sluice gate with two smaller gates to give greater flexibility in maintaining them and create space to install fish and eel passes. The supporting walls for the new gates will be of reinforced concrete for strength and durability.

Above: Steps down to where the eel pass will enter the water, downstream of the sluice

We built parts of these new walls in autumn 2022. We allowed the sluice to work normally over the winter, when higher river flows occurred. During the winter we installed new cabling ducts, steps to where the eel pass will enter the water downstream of the sluice and modified the existing control building in preparation for the installation of new equipment.

We will be returning to in-channel works shortly to start finalise the construction of the walls and installation of the new gates.

We will isolate the sluice with a temporary dam to be able to work safely inside it. We will have measures in place to manage the normal river flows around the sluice, though if necessary, we will partially remove the temporary dam to allow flood flows through the working area. We will first construct some sections of walls upstream, similar to those completed downstream last autumn. These will separate the two gates and planned fish and eel pass. Once these are complete and strong enough, we can prepare for removing the existing sluice in the summer and build the walls to support the new gates. We will also replace the access footbridge over the sluice and carry out improvement works throughout the sluice compound.


The waterways in the Lower Lee valley include the River Lee Navigation, Old River Lea, and the Lee Flood Relief Channel (LFRC). The LFRC was built between 1949 and 1977 and is designed to carry flood water to reduce the likelihood of flooding in the Lower Lee valley. A system of weirs, gates and sluices control water levels in the LFRC. These maintain water levels for water supply, navigation, amenity and environmental purposes while allowing flood flows to pass during storm events.

Hardmead Sluice is a major flood control structure within the LFRC and is located at Great Amwell, close to the town of Ware in Hertfordshire. As well as managing flood risk, the sluice assists in sustaining water levels in the River Lee Navigation that also enables flows down the River Lee Amwell Magna Loop from the Tumbling Bay weir.

What we are doing

We are replacing and improving the gates and operating equipment at Hardmead Sluice as the existing ones are now reaching the end of their working life after 45 years of service.  A failure of Hardmead Sluice would result in increased flood risk and loss of control of upstream water levels.

Replacing the sluice gates and their operating equipment will maintain the conveyance of storm flood flows through the structure to sustain the current level of flood management and to maintain the ability to control upstream water levels for navigation, water supply, amenity and environmental needs. 

The existing sluice also acts as a barrier to the free passage of fish and eels.  As part of this project new fish and eel passes are being constructed to enable the free passage of fish and eels around the sluice. This will help increase the length of watercourses these species can migrate along, extending their range and improving the aquatic biodiversity of the watercourses.

The main works started in August 2022 with a pause during winter 2022-23 and are expected to be completed by March 2024.

How will the sluice replacement affect you?

During the main works you may notice additional temporary construction noise during the working week. Construction vehicles will be entering the site from Hollycross Lane via the private access road and across Amwell Bailey Bridge. Public Rights of Way will not be impacted but there will be a minor diversion for pedestrians at the northern extent of the site boundary. Road closures should not be required.

There are other construction works further along the Lee Navigation near the Amwell Marsh Bridge towards Stanstead Abbots, though these are unconnected to the Hardmead sluice replacement project.

Are you prepared for flooding?

While these works will improve flood defence along the LFRC, it is important to be prepared should the worst happen. Here are some steps you can take to prepare yourself for flooding events:

Sign up to our flood warnings: www.gov.uk/sign-up-for-flood-warnings

If you are visiting the area, sign up to flood warnings or the Met office weather alerts and receive advance warning of potential flood risk: UK weather warnings - Met Office

Prepare a personal flood plan and be assured of what to do if it floods: Personal flood plan - GOV.UK (www.gov.uk)

Thank you for visiting our project information page.

If you would like any further detail about any of the above information please get in touch at PSO-HNL@environment-agency.gov.uk


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  • Flood management