Scientists question worth of natural flood defence schemes

Natural defence schemes such as tree planting are not "a silver bullet" for stopping flooding, scientists have warned.

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Can tree planting really help prevent more Cumbrian floods?

Natural flood defences are unlikely to prevent major flooding, scientists have warned Credit: PA

Ever since Storm Desmond wreaked havoc across the region in 2015 there have been increasing calls for tree planting to be used as a way to reduce flood risks.

Campaigners have called for thousands of trees to be planted to help prevent a repeat of the flooding that devastated so many communities, but now scientists are questioning the effectiveness of natural flood defence schemes.

A Royal Society report published today says initiatives such as planting trees and creating wetlands are not "a silver bullet" for stopping flooding.

It warns that 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 author Dr Simon Dadson, of the University of Oxford, told ITV Border:

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.

Our analysis showed that trees can help with minor flooding and improve the condition of the soil, but any extreme weather will soon saturate the ground and they cannot be relied on to defend communities.

– Dr Simon Dadson, of the University of Oxford

He warned that some extreme flooding, such as that caused when Storm Desmond hit parts of the UK in December 2015, could be "simply overwhelming" in the future.

Cumbrian-based Professor Louise Heathwaite, of Lancaster University, also worked on the report and said that while there might be no evidence to show the measures work at scale, they have other potential benefits.

Our analysis of the evidence shows there is no silver bullet solution to flooding in places like Cumbria based on natural flood management, except perhaps at small scales.

“But we must not lose sight of the long-term benefits for our landscapes for storing carbon, reducing soil erosion and boosting wildlife, together with the fabulous efforts of local communities to work together to increase their resilience to local flooding.

– Professor Louise Heathwaite, of Lancaster University

Peter Leeson, of the Woodlands Trust, said the charity has been involved in several schemes to plant thousands of trees including the planting of 126 hectares on Tebay Fell.

He admitted that tree planting was not a solution to flooding, but said it had to be “part of the mix”.

“The way the fells have been managed in recent years means they do not deal with water particularly well. There is a lack of complexity in the vegetation and the friction that vegetation creates and the ground has been compacted by animals.

“Tree planting will make a difference and have many other benefits such as providing shade for rivers which is important to control temperatures and protect fish,” he said.

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