Expert Witness

River ecology under threat from old-fashioned practices

Thursday, February 6th, 2014

On an icy cold January morning a crowd of enthusiastic volunteers armed with spades and woodsaws met at a North Norfolk village with ambitious hopes of restoring a section of the Gunthorpe Stream. This stream, a tributary of the beautiful River Glaven, has in the past few decades been overdeepened, overstraightened and widened to more than twice its natural width, due to river management strategies that since the 1950s have destroyed much of our natural lowland river habitat. The aim of these strategies was to help reduce flooding of farmland in the headwaters by speeding the passage of water along rivers. Instead, such management appears to cause greater flood risk to land and communities downstream and the loss of valuable habitats through direct destruction and drainage.
Rivers are dynamic, ever changing habitats, rich in wildlife, if they can evolve naturally, but the belief lives on that canalising and dredging is the solution to our land management and flooding problems. Our ecologist Alex Prendergast says that instead, there should be more careful planning of new development safely away from floodplains and that we need to urgently restore our river and wetland habitats. Here is how Alex and his team are restoring the River Glaven.
“The River Glaven Conservation Group was assembled in the freezing mist on Thornage village green. We could see that given the slightest opportunity, this stretch of stream would try to restore itself: a concrete pipe left in the channel had diverted the stream into the opposite bank creating a natural river cliff and encouraging the formation of a vegetated side bar and a series of small waterfalls. A wooden debris deflector installed in the previous year, had already resulted in the formation of a well-oxygenated gravel bed used by spawning brown trout, and a downstream scour pool where large fish can rest and feed. Assisted by a national expert in river ecology and geomorphology, staff from the Environment Agency and a JCB digger, our plan was to install a variety of similar wooden structures in the channel, fashioned from nearby alder trees”.River Graven
We split into several groups. My group liked the idea of making a horizontal submerged barrier to encourage bed scour and increase water movement. After half an hour of sawing, digging and splashing, the job was done and we could immediately see the change it was causing to the channel – instantly the silt was being scoured away to reveal a gravel bed and a standing wave above the structure made a great babbling noise – this little section was alive again!
Altogether we made about 15 features along a kilometre of the stream, using the digger to help speed the process of moving gravels and creating scour pools, which the river would eventually do itself over several years. Throughout the day it was clear that the water level at the top of the works area was becoming higher and higher – that is, the water was being slowed and retained for longer in the headwaters.My beautiful picture
The day was good fun with a friendly if chilly crowd. It is hoped that the improvements we made to the stream will allow charismatic species such as brown trout and white-clawed crayfish to use the stream once again”.

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