Western Morning News story by Martin Hess reports study showing beavers as, “A natural ally in the fight against flooding.”
The report based on a groundbreaking 5-year study conducted by Professor Richard Brazier of University of Exeter’s Geography Department shows that not only do beaver dams help retain water and reduce run-off but also create a habitat that serves to clean water of pollutants.
Prof Brazier explained: “My job is to monitor the changes, then to see what difference these animals make over a number of years. So what I’m doing here is looking at flood attenuation. Is beaver activity changing the flow regime – the water that’s coming in compared with what’s leaving the site? Can they play a role in mitigating flooding?
“The second is water storage, specifically in dry times. Can more water be stored in this woodland landscape and therefore benefit streams and reservoirs downstream?
“The third is water quality. Have the beavers essentially created a natural filter for quite polluted water coming off agricultural landscapes?”
Asked why such an experiment had never been done before Prof Brazier replied: “It’s not easy in the wider landscape. In an experiment like this there is one stream in, one stream out, so we can control what’s going on. But there is another aspect – studying it in the UK, in this lowland intensively farmed landscape that we have, is important. If you want evidence to discover what beavers will do in our landscape you really have to study the animals here.”
He explained how the 13 beaver dams are slowing the water flow. “The water comes in at the top and fills up behind the first dam, overflows and fills the next. It is like a staircase. There is a constant release of water – each pond draws down and is replenished before the next rainfall.”
Professor Brazier calls beavers a ‘keystone species’ precisely because their dams create habitat for other species.
We had just 10 frogspawn clumps here in 2011 – and we had 580 clumps last week.
Those industrious beavers build dams that actually serve to purify water in this mountain stream, the same water is sourced for drinking water downstream.
“From this landscape here we are seeing an average of 150 mg per litre of sediment coming off farmland in storms. But what we see leaving the site here is just 15mg per litre. Behind every one of these dams the water slows until it’s practically not moving – the sediment settles and fills the pond.
“If you are water company and a river has high sediment, it costs a lot of money to treat. Nitrogen and phosphorus both enter this site at reasonably high levels especially in storms – but at the bottom end we see so little in nitrogen and phosphate, the university’s equipment cannot actually detect the minute amount.