‘Natural defences no silver bullet’ on flooding

Mytholmroyd centre under water after the River Calder burst its banks.

Mytholmroyd centre under water after the River Calder burst its banks.

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Natural defence schemes planned for the Calder Valley such as planting trees and creating wetlands are not “a silver bullet” for stopping flooding, academics warned today.

Researchers have claimed natural measures to manage the risk from rivers could play a valuable role in curbing floods, particularly on a small scale.

But a lack of monitoring of existing schemes means their potential is unclear, and the hope they could stop the worst floods is not backed by evidence.

Lead research author Dr Simon Dadson, of the University of Oxford, said: “What we’ve found is that when it comes to natural flood management, there are some interventions for which there is very strong evidence, but these tend to be in small-scale river catchments. One of the main problems decision-makers face is that differences between catchments make it difficult to transfer evidence from one location to the other – and we don’t yet know whether the effects in small catchments can be extrapolated to larger ones.”

The analysis follows the announcement last month that 200,000 trees will be planted in Calderdale’s Calder Valley, as a new natural flood defence under plans by Yorkshire Water.

The area was among the worst-hit in Yorkshire in the 2015 floods.

During a visit to the town of Mytholmroyd last month, Flood Minister Therese Coffey looked at designs for a new alleviation scheme using traditional and natural defences in Calderdale.

Ms Coffey said: “The memories of last winter’s floods won’t soon be forgotten, but I want to reassure the communities across Calderdale that we are investing to better protect your homes, businesses and families. We have committed over £50m to improve flood defences across the Calder Valley by 2021 – combining traditional defences with natural measures to slow the flow upstream.”

The new study has been published in the Proceedings of the Royal Society after being compiled by a team of experts, including Professor Joseph Holden at the University of Leeds. It said natural schemes range from creating water storage areas such as ponds, reservoirs or wetlands to planting buffer hedges, changing grazing or crop-growing in fields.

Lead author Dr Dadson warned extreme flooding could be “simply overwhelming” in the future.

He added: “Natural flood management can help if implemented well in carefully chosen locations, and it can bring important benefits to landscapes and wildlife, but it’s not a silver bullet for the problem of flooding.”

A spokeswoman for the Environment Department said: “We take a long-term, strategic approach to protecting the nation from floods – carefully looking at flood risk across an entire catchment area and using natural flood management measures alongside hard, engineered defences.”