Engineering work restores rare riverine habitat and its rich biodiversity
With the help of bioengineering company Salix, the Norfolk Rivers Trust is improving fish and other river wildlife habitats on the River Babingley near Flitcham, one of only 200 chalk rivers in the world.
The River Babingley rises from chalk springs above the villages of Flitcham and Hillington in northwest Norfolk, meanders through the Royal Sandringham Estate and joins the sea through Wootton Marsh and the Great River Ouse.
The river provides habitats for eels and migratory freshwater fish, including bullhead and brook lamprey, as well as waterway mammals, such as water voles and otters. It is also important for birds such as buzzards, barn owls and kingfishers, and invertebrates including damselflies and dragonflies.
‘Despite centuries of modification, the upper Babingley remains one of the finest, clearest and cleanest stretches of chalk river in Norfolk,’ says Johah Tosney, manager of Norfolk Rivers Trust’s Nine Chalk Rivers Project.
It is particularly special as there are now only around 200 true chalk streams left in the world, he adds, ‘of which 15 per cent are here in Norfolk’.
Rainwater soaks through chalk ground and, cooled and filtered by its journey through the chalk, emerges at a constant temperature and with a clear and alkaline quality. This makes chalk rivers ‘England’s rainforests’, Jonah argues, ‘providing a perfect, gentle habitat in which everything grows abundantly – insects, water plants, fish, crayfish, birds and mammals, including the critically endangered water vole’.
Sadly the World Wildlife Fund’s recent ‘State of England’s Chalk Streams’ report notes that 77 per cent of our chalk streams are failing to meet the good status required by the EU’s Water Framework Directive, he adds. Hence Norfolk Rivers Trust is working with the Environment Agency, Natural England and the World Wildlife Fund to deliver a programme of river restoration measures to improve nine chalk stream habitats in Norfolk.
The River Babingley had been straightened and controlled in places, with steep man-made banks and weirs. It also suffers from silt build-up from local roads and farms. The weirs back up water, slowing the flow and ponding the river. They also make fish passage difficult, as water surges through a narrow opening, making life difficult for less able swimmers such as bullhead and stone loach.
Where channels have been straightened and lowered, a more uniform habitat has been created which can be exploited very well by a small number of species but will exclude many others associated with chalk rivers.
Work on the River Babingley restoration project at Hillington includes removing an old weir and restoring more natural channel shapes and flow patterns. In the past, the river powered many mills, hence the man-made modifications to control its flow.
‘We are using local timber and gravel for channel re-shaping, narrowing and deepening, offering a more diverse range of passages and variations in water movement,’ explains Salix project manager Chris Mackintosh-Smith. ‘As well as creating riffles and eddies in the water, the wood and the gravel provide places for the fish to hide from predators and seek shade from the sun. And they offer another habitat layer for invertebrates, which in turn provide food for the fish.’
He adds: ‘We have also removed the wing wall and lowered a sill at a brick weir to improve river continuity and make it easier for fish to pass through this reach, and we’ve installed a timber footbridge for access.’