Could beavers be introduced into the Calder Valley to reduce flood risk?

This is one of the first questions Slow The Flow is asked when we talk about Natural Flood Management (NFM). For sure, Beavers are natural engineers and like to create dams. Those dams, in a small way, store water and reduce flow downstream.  That is just what Slow The Flow do on the smaller tributaries, with the 600+ leaky dams we have installed at Hardcastle Crags with The National Trust. We all agree that it is best to work with nature rather than against nature. What is not to like? 

The Calder Valley is not their natural habitat

Beavers tend to thrive in slower floodplain rivers and flatter terrain, made up of forestry and open space, rather than the steep sided valleys of Calderdale. Extensive areas of forestry and water are where the largest beaver colonies are to be found and similar areas have been sought out in the UK. A feasibility report produced by Natural England found the optimum habitat for beavers were more suited to the wide flood plains on gentle gradients.  Slow the Flow Trustee, Robin Gray, visited the reintroduction site at Knapdale in Argyll. He said, 

“In Argyll, the forestry was on former peatland with extensive flat lagoons and pools.  Families of beavers tended to use timber to extend existing water bodies to create wide and shallow pools rather than damming main rivers or tributaries. There were great ecological benefits, with beavers creating a more diverse habitat, creating glades for ground flora or changing the form of the riverbank”. 

In Yorkshire, there has been a successful introduction by the Forestry Commission at Crompton Forest in Pickering. Closer to home there has been some discussion to look at the reintroduction of beavers to areas of plantation at Gisburn Forest in Lancashire.  So, why not enlist beavers to carry out this task here in the Calder Valley? 

Rosie Holdsworth of the National Trust has considered reintroductions: 

“The Calder Valley’s rivers and watercourses have, almost without exception, been modified in some way by humans in the past. Our rich industrial history has left a legacy of river walls, weirs, modified channels, goits, bridges, sluices, and mill ponds. As humans we always take these alterations into consideration when planning our leaky dams to avoid any unintended consequences, but beavers might not be so predictable. Similarly, there is a lot of ongoing human activity and disturbance within the Calder Valley. Unlike other trial areas, there isn’t much quiet undisturbed space in our valley bottoms. Conflicts between beavers and site users would be likely and could lead to poor welfare outcomes for them and alter their population dynamics.” 

They could make flooding worse in our area

There might be other unintended consequences of reintroduction of beavers in an extreme rainfall event. Where we have our steep sided valleys, like here in the Calder Valley and ‘high-energy’ water courses, additional debris brought down in an extreme event might cause blockages under bridges or to essential flood management infrastructure (such as trash screens) making flooding issues worse.  In contrast, our ‘human beaver’ leaky dams are carefully constructed with this in mind, ensuring that materials used are properly anchored.

Working with natural processes is never entirely free of risk and managing the unforeseen consequences of introducing species must be carefully thought through.