Rare chalk stream in Hemel Hempstead could be rerouted after long periods of 'human intervention'

A rare chalk stream in Hemel Hempstead could be rerouted after long periods of “human intervention”.

The Environment Agency plans to cut a new channel for the River Gade through a Hemel Hempstead park in a bid to improve water quality and prevent flooding. Dacorum Borough Council has green-lit the plans, which would involve short-term construction works in Gadebridge Park.

Local authority staff who reviewed the plans said they aim to “strike a balance” between the needs of wildlife and the surrounding community which uses the green space.

“The River Gade is one of very few chalk streams that exist worldwide,” a report to support the Environment Agency’s case reads.

“Chalk streams are unique river systems that provide a variety of habitats, however, the majority of chalk streams in the UK fail to meet the ‘good’ status required by the Water Framework Directive.”

It adds: “Historically, the River Gade has been impacted by human intervention which has created an over-wide and frequently perched channel (where the water surface is higher than the surrounding floodplain).”

According to the Environment Agency, this has “exacerbated” the amount of fine sediment in the Hemel Hempstead area, which supports heavy vegetation growth when the flow is low.

This can cause flooding to the surrounding green space when river levels rise, and water collects in low-lying areas of Gadebridge Park.

The report adds the existing concrete weir in the park, which was built in a bid to regulate water flow, “acts as a barrier to fish passage and impounds water upstream, preventing natural channel processes from occurring”.

Realignment would take place between the Grade Two-listed White Bridge – which will be protected – and the B487 Queensway. Two new bridges would be created and the existing channel would be filled in.

According to the Chiltern Society, which aims to support nature recovery in the Hills, chalk streams play host to water vole – endangered in the UK – and brown trout, which is “threatened” as a result of habitat loss and climate change.

A comment by the society on the Dacorum Borough Council website reads: “This land is always susceptible to flooding, being in the River Gade floodplain, so [realignment] may not alleviate the situation.

“If the authority is minded to approve it, then the society would request that the reeds and foliage along the embankment be restored as these trap pollutants, which is particularly important given the propensity of pollution in England’s rivers.

“A sterile river embankment is not only useless to the aquatic flora and fauna but unattractive and ‘manufactured’ in appearance.”

Dacorum Borough Council approved the plans with 13 conditions for developers.

These set out that more detail is needed around how construction workers will manage the surrounding ecology and landscape, and that the developer must probe the potential “archaeological significance” of the site.

“This project has taken a significant period of time to come to fruition,” an officer report reads,” a council report notes.

“It seeks to provide an optimal solution in relation to the aspirations and views of the Environment Agency, Dacorum Borough Council, Affinity Water and the Friends of Gadebridge Park as stakeholders and the wider population and users of the park.

“Fundamentally, the project seeks to strike a balance between wildlife and environmental needs, and the ability for the park and river to be enjoyed by the community.”