Magdalen College has applied for permission to repair the wall along Addison’s Walk, which borders the Cherwell opposite Magdalen Bridge. The collapse has been blamed on signal crayfish – an invasive American species that has populated many of Britain’s rivers – and the position of the wall on an outside bend of the river.
But the college has warned the bank is “badly degraded” and could threaten the waterside walks – part of the Grade I-listed Water Meadow – if is not repaired, documents lodged with Oxford City Council show. It has proposed rebuilding the wall with new concrete supports underwater and trench sheet.
The documents say: “The works will sensitively reinstate and stabilise the bank and ensure these grounds continue to remain in use.Owing to the seriousness of the bank erosion – much of which is caused by burrowing crayfish and high flows over slumped clay – the professional advice received is that proposals put forward represent the only viable options”
The signal crayfish, or Pacifastacus leniusculus, is a predator with a “ferocious appetite”, according to the Environment Agency. It feeds on fish, frogs and invertebrates, as well as plants, and even eats individuals of its own species. In the winter it takes shelter by creating burrows in river banks that can be up to two metres deep, entering a kind of hibernation.
Bob Rice, known as ‘Crayfish Bob’, has been trapping the lobster-like assassins for 14 years in a crusade to slow their invasion of the Thames.
The 61-year-old, whose narrowboat is moored at Abingdon, said: “They are a huge problem and their burrowing into the banks is a very common cause of erosion.We have traps in the Thames that catch a lot of them but it is an uphill struggle and that’s why we need to increase demand for them” Mr Rice has taken a ‘pop up’ store to Glastonbury Festival every year since 2011, where he sells crayfish gumbo. He added: “My approach is to help get rid of them by selling them and coming up with various products which I take to festivals. The objective is to eventually make them popular enough to get them on supermarket shelves but it is going to be a long battle.They are rightly considered a menace because of the damage they do, everything in the river can be affected by them”
An Environment Agency spokesman said it was “unusual” for the crayfish to cause structural damage to walls along banks, adding “It is illegal to take non-native crayfish, by any means, without a permission from the Environment Agency in England”
No-one from Magdalen College was available to comment.
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