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Re-wilding the River Bure: Low cost river restoration

07-Jun-2013

‘How should a river be restored?’ can often be translated as ‘How much will it cost?’
One inexpensive low tech approach, that has sometimes led to divided opinions, is now gaining acceptance as a suitable method of restoring natural riverine processes.
 
A pioneering plan to recreate natural tree-fall was carried out on the River Bure, a chalk stream on the Bickling Hall Estate in Norfolk. The only equipment needed was an old boat, a hand winch and a chainsaw.
 
See the re-wilding of the R. Bure in action here

Like many other British rivers the River Bure had been engineered and cleared of trees for flood prevention and navigation. The river had also suffered from over-widening due to historic dredging activities and was heavily silted. Wild trout stocks and overall conservation value was relatively low.

 
Dave Brady from the National Trust, one of Britain’s leading conservation charities, was the project manager for the venture. He identified an opportunity to use a  straightforward, no frills approach by felling entire trees into the river to diversify the flow and restore habitat. The approach, although it is simple, is grounded in scientific theory.
 
Dave Brady said,
‘It was this idea of exerting a simple influence that guided my approach to the ‘restoration’ work on the River Bure .
 
For many decades the desire to keep the water moving resulted in all ‘obstacles’ being removed so the most simple approach to restore natural processes would be to stop removing large woody debris, and to do the opposite by re-introducing it.  Taking into account increased flooding of upstream meadows trees were felled in to the river and left roughly where they fell to start the natural ball rolling.
To me restoring or re-wilding is, in simple terms, allowing nature to resume the management of our environment with, wherever possible, no new negative influences from man and a minimum of designed restoration’. 
 
The  problems resulting from re-introducing large woody debris into rivers are generally identified as changes to the river flow and also a genuine issue of  material breaking loose and blocking culverts. There is also a public perception that a river that was previously reliant on dredging for maintenance will be made more liable to flood. 
 
However, according to findings by the Environment Agency (England) unless woody debris is blocking more than 10% of the cross-sectional area of a river it is unlikely to impact on water levels, therefore it will not increase flooding.  Trees and other woody debris reintroduced to the river can be anchored to prevent possible movement and if debris is directed in a downstream direction and positioned close to the bank it will reduce bank erosion with little effect on channel shape.
 
Dave Brady explains that ‘Nature will always take advantage of opportunities that are either of its own making or have been provide by man’.
 
As a result of this approach water now flows faster, moving silt and sediment to clean and expose gravel. This provides spawning grounds for a now thriving population of wild trout. Silt is now trapped in the slack pools behind the woody debris and provides opportunities for colonisation by plants and habitat for invertebrates and fish.
 
The restoration of the River Bure is one of the case studies on our RiverWiki you can also find information about visiting the site on the National Trust’s website .
For further information contact: Dave Brady (Head Ranger), National Trust dave.brady@nationaltrust.org.uk