Can Beavers Reduce Flooding? The Case of the River Otter
Six dams made of branches and mud, built by beavers upstream of an English village, lowered water peaks during storms. A study by the University of Exeter measured by how much.
The Return of the Beaver to Great Britain
Beavers had been extinct in Great Britain for around 400 years. The cause was hunting.
In 2009 they returned to Scotland, with four families brought over from Norway. It was the first authorised reintroduction of a mammal in the United Kingdom.
The Beavers of the River Otter in Devon
In 2015 it was England's turn. Two pairs were released on the River Otter, in the county of Devon.
The population grew within a few years. By 2019 there were at least eight families in the area, and 28 dams had been counted on the river.
Do Beaver Dams Flood the Surrounding Fields?
When you think of a dam, it's easy to picture waterlogged fields. The data from the Otter show a different picture.
The 28 dams held back water along just 1.9 of the 594 kilometres of watercourses in the catchment. In other words, 0.3% of the total.
That doesn't mean there were no problems. At five locations, the dams damaged farmland.
There were also benefits for wildlife. The pools created by the beavers held 37% more fish than stretches without dams.
What Peak Flow Is and Why It Matters
In a flood, what swamps a street isn't just the total amount of water. It's the peak that arrives all at once.
That peak is called the peak flow. The higher it is, the greater the risk of the river bursting its banks in populated areas.
The University of Exeter Study: 30% Lower
In 2020, a University of Exeter study looked at the effect of a single beaver family. That family had built six dams upstream of the village of East Budleigh.
The researchers compared the water flowing into the dams with the water flowing out during storms. On average, peak flow leaving the dams was 30% lower than peak flow entering them.
No engineer designed this flood barrier. The beavers built it out of branches and mud.
Frequently asked questions
How much did beavers reduce flooding on the River Otter?
According to a 2020 University of Exeter study, the peak flow leaving six dams built by one beaver family was on average 30% lower than the peak flow entering them during storms.
When did beavers return to England?
In 2015, when two pairs were released on the River Otter in Devon. By 2019 there were already at least eight families.
Do beaver dams flood large areas of land?
On the Otter, the 28 dams held back water along just 0.3% of the watercourses. Even so, they damaged farmland at five locations.
Why did beavers go extinct in Great Britain?
They were wiped out by hunting and had been extinct for around 400 years. They returned to Scotland in 2009 with four families from Norway.
Informative article written with the help of AI tools from the verified script of the video. The video is in Spanish.