Thames Water have been accused of another botched job, this time on the River Wandle near Beddington, where their works have made it impossibly difficult for fish to swim upstream.
Botch job: how Thames Water’s new ‘boulders’ have made a river impassable to fish
A local environment campaigner has an email from the Environment Agency which says that the privatised water monopoly ignored advice over the demolition of a weir by the Goat Road bridge.
Jim Duffy had expressed his concerns before it was decided to demolish the weir. But his worst fears have been confirmed, after the weir was replaced by a series of concrete “boulders”.
“The fish now find it too difficult to swim upstream because of the strong currents formed by the boulders,” Duffy said.
The weir at Goat Bridge was about five feet high. Its removal was supposed to bring together disconnected sections of the river at Mitcham. “The weir currently means that a variety of aquatic wildlife such as fish and insects cannot reach a variety of habitat to complete their life cycles,” according to South East Rivers Trust before the project went ahead.
“This structure weir restricts about 500 metres of river, creating water conditions more akin to a lake than a river and leaving wildlife unable to reach a variety of habitats crucial to their survival.”
The Wandle is a rare chalk stream, which rises in South Croydon to flow northwards towards the Thames at Wandsworth via Carshalton and Mitcham. Historically, it provided habitat for a range of fish, including trout.
Thames Water conducted the work earlier this year, and replaced the weir with a rock ramp and concrete boulders.
Wandle weir: the water course at Goat Road bridge before the demolition
Duffy’s letter from an Environment Agency official stated: “We are well aware of this issue at Goat Bridge… [This] is a problem with the short box culvert immediately downstream of the rock ramp which has had a series of concrete ‘boulders’ created within and downstream of it to cause variations in water depth and thus enable fish passage…
“We have a dedicated panel of fish pass specialists and despite their feedback being given on the proposed design from Thames Water, with suggested alterations, the alterations didn’t get made.
“We are investigating what changes need to be made to our processes at the EA to ensure that feedback from the fish pass panel doesn’t get ignored in future.
“Rest assured that the design is stable and safe and does not increase flood risk… but there is still a question mark over what depths the concrete boulders will create and what species of fish it can pass. This is currently being investigated by flow monitoring.
“As a result, we haven’t yet signed off the project as complete. It is a shame that the Goat Bridge project wasn’t able to demolish the problem culvert completely but I think it will be later used as a cycle path.”
Duffy said: “The EA has been asked if similar plans to knock down the weirs at Wilderness Island can be put on hold. Concerns there include ponds on the nature reserve drying out and reduced water levels by residents’ homes creating security risks.”
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