Scientists say beavers can help fight floods

Cute swimming beaver in murky lake water

When flooding caused widespread devastation in Alyth last summer, many pointed the finger at a colony of beavers living upstream.

There were claims that, during a morning of freak downpours, trees and branches felled by the rodents were washed into town and clogged up bridges, leading to dozens of homes and businesses being swamped.

Days after the catastrophe, the Scottish Association for Country Sports said there was evidence beavers had been an “exacerbating factor”.

Most residents refused to accept the claim and the theory was later dismissed in an official report into the flooding.

Now, a group of Scottish academics believes the area’s beaver population may have helped the situation by slowing down the flow of water. They claim colonies could even have helped prevent future flooding and protect properties.

Researchers from Stirling University studied beaver families living around Alyth. They found beaver dams helped to mitigate flooding by storing, then slowly releasing, water.

The study, part of a 13-year programme of research, also helped to improve wildlife habitats in the area. Scientists said all beaver dams near Alyth remained standing after the incident in July, as well as more recent flooding.

Dr Alan Law, who is co-author of the paper, said: “What we found was, downstream of these dams, the water level doesn’t get to the same height as it does upstream.

“Also, the time it takes to get to this height is much longer, by several hours. What really happens is, these beaver ponds act like sponges by absorbing most of the water and then slowly releasing it as time moves on.”

He said: “This is one of the largest mammals that have been formally reintroduced into the country and there’s always going to be a nervousness about that. But, at the same time, this is an animal that was here before and definitely has more benefits than negatives.”

As part of the study, areas where beavers were known to have been active were compared with sites at which they were absent.

Dr Nigel Willby, of Stirling University’s School of Natural Science, added: “Our work points to the fact that by having the beaver dams present on a stream, the floods are locally mitigated as these dams store and slowly release water unlike the un-dammed, straight streams where water flows without obstacle.”

An official report concluded that the flooding was caused by a months’ rain falling on the town over a period of six hours. However, this theory has also been questioned by locals, who say that the area has escaped further flooding despite even heavier rainfall at the start of the year.