The River Gade has returned to its natural course in Gadebridge Park, following an ambitious river restoration project delivered by the Environment Agency, in collaboration with Affinity Water, Dacorum Borough Council and contractors BAM Nuttall.

Photo: April 25 the moment River Gade was diverted into the new channel

JBA Consulting carried out an initial feasibility study for Gadebridge Park from 2016 to 2018 in consultation with all project partners and key stakeholders.

The project has reconnected the chalk stream to its natural floodplain, improving wildlife habitats, reducing the risk of localised flooding downstream of the white bridge in Gadebridge Park.

The Environment Agency and Affinity Water funded the river restoration project and Dacorum Borough Council contributed to its recreational and amenity aspects for the park.

Historically, the River Gade was diverted from its natural course to supply water to the former Bury Mill. This artificial channel, perched on the edge of the park, caused the river to become disconnected from the surrounding landscape, leading to reduced flow, water quality issues, and limited biodiversity.

The restoration involved creating a new river channel through the centre of the park, bringing the Gade back to its natural position in the valley bottom. The works included the installation of two new footbridges, a gauging station to support the flood warning system, and an innovative ultrasonic structure that allows fish and mammals to move freely while also redirecting spring flows vital for chalk stream ecology.

Chris Wilson, area director at the Environment Agency, said:

“Getting to this stage marks the huge collective effort of a large number of people, not just at the Environment Agency, but from our partners, Dacorum Borough Council and Affinity Water, our contractors, JBA, BAM Nuttall and Arcadis and many, many others besides.

“I’d like to thank everyone involved for their perseverance and commitment to bringing such a complex and ambitious project to completion.”

A new channel was dug through the centre of the park and the project provided two new footbridges for the park.

Extra gravel added to the channel to help shape the river and restore natural processes typical of a chalk stream. This includes riffles – shallower areas of the river where faster-flowing water pass over gravels and cobbles on the riverbed, adding oxygen to the water - and replicating natural ‘gravel bars’, which are deposits of gravel where the river’s energy is lower, creating varied water depths for river plants and animals to thrive.

Creating vegetated margins along the banks of the new channel will provide important habitat for many species - for example, a habitat and a source of food for aquatic insects at different life stages, refuge from predators for juvenile trout and water vole, and even a migration corridor for otter. As well as providing habitat, vegetated margins also play an important role in filtering sediment and reducing nutrients entering the watercourse, helping to improve water quality. They can also slow flood flows and help to reduce erosion of the banks.

Councillor Robin Bromham, portfolio holder for neighbourhood operations at Dacorum Borough Council, added:

“This is a landmark moment for Gadebridge Park and for our local environment. The return of the River Gade to its natural course not only restores an important ecosystem but also enhances the park experience for our residents and visitors. We’re proud to have worked with our partners to deliver this project that benefits both people and nature.”

The project is important for a number of reasons –

• Only 17% of chalk streams are in their natural state. 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. All chalk streams in England, including the River Gade, face vast challenges and pressures from decades of mismanagement.
• The artificial channel is much wider and straighter than a natural chalk stream would typically be. This often leads to a build-up of sediment along the bank and associated excessive vegetation growth, which gradually narrows the channel. The river had little resilience to drought conditions due to low volumes of flow, especially in late summer and early autumn.
• Re-routing spring flows - which are currently diverted through a culvert, or 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.