9. Gadebridge Park river restoration project

Aims: Involve people with their local waterbodies; Improve wildlife corridors; Manage flow; Work together

Water body: River Gade

Project description

The Environment Agency is working with Dacorum Borough Council and Affinity Water to help restore the River Gade at Gadebridge Park, a globally rare and valuable chalk stream. The project will provide multiple benefits, including improved habitats for wildlife, the protection of water resources for both people and the environment, and allowing local residents and visitors to get closer to the river and enjoy nature.

Like many chalk streams, the River Gade faces pressure from low flows and historic modifications to its channel that limit the river’s habitats and the wildlife it can support. In Gadebridge Park the River Gade flows down an artificial channel created to supply water to the now demolished Bury Mill. The artificial channel is ‘perched’, meaning that it sits at a higher level than the valley bottom - the natural course of the river through the park. This means that the river is disconnected from its floodplain. When flooding occurs in the valley bottom, the water remains in the park for long periods of time because it is unable to flow back into the channel.

The artificial channel is much wider and straighter than a natural chalk stream would typically be. This can lead to a build-up of sediment and excessive vegetation growth along its banks, which gradually narrows the channel. Due to its low volumes, the river has little resilience to drought conditions, especially in late summer and early autumn. The weir at the Environment Agency’s Bury Mill Gauging Station and other remains of historic in-channel structures also act as barriers to fish. These structures can cause sediment and vegetation to build up, impacting on river habitats and wildlife.

The river suffers from low flows due to spring flow (groundwater emerging at the surface) being diverted into an underground tunnel (culvert), pressure from water abstraction for public water supply and from being disconnected from the groundwater table.

In Gadebridge Park the river’s natural course along the valley bottom can still be seen during wet winters, when groundwater rises to the surface where the river would have been. The Environment Agency, Dacorum Borough Council and Affinity Water's project will realign the river channel back to its original course along the valley bottom. Together with other planned improvements, the project will provide multiple benefits for both people and wildlife.

 

The current proposals include:

• Realigning the part of the River Gade located downstream of the Grade II listed White Bridge back to the valley bottom (through the centre of the park at its lowest point). This will reconnect the river to its floodplain and to the groundwater table below.
• Re-routing spring flows - which are currently diverted through a culvert (underground tunnel) and discharged into a fishing lake at Kings Langley 5km downstream - into the new realigned channel. This will provide additional flow to the river, increasing its resilience to low flows, improve the river’s water quality and help to restore natural characteristics of a chalk stream such as a more alkaline PH and a stable temperature all year round.
• Replacing the existing Bury Mill gauging station with a gauging station on the new realigned channel that is passable to fish and has a reduced impact on the river.
• Creating vegetated riparian margins alongside the river channel to provide new habitats for wildlife.
• Providing new footpaths alongside the river, a fully accessible bridge crossing the new realigned channel from the Queensway carpark to the Bowls Club and an informal crossing point in the centre of the park - all for people’s enjoyment of the river.
• Providing dipping platforms and gravel beach areas for people to get closer to nature.
• Installing information boards within the park to share the River Gade’s historical importance to the landscape and help people to understand and value our rare chalk streams.

 

Overall, the project will provide multiple benefits, including improved habitats for wildlife, the protection of water resources for both people and the environment, and allowing local residents and visitors to get closer to the river and enjoy nature.

For more details about the project, including updates on its progress, please visit the project information page. You can also sign up to receive updates via email by contacting This email address is being protected from spambots. You need JavaScript enabled to view it..

Project lead: Environment Agency

Project partners: Affinity Water, Dacorum Borough Council

Contact for more information: This email address is being protected from spambots. You need JavaScript enabled to view it.

Project start: 2015