Research & Conservation Officer, Jonny Grey, is thinking laterally with a new project on the Upper Aire
If I’ve been working on connectivity this summer, it has been mostly longitudinal! Reinstating fish passage and sediment transport on fragmented channels have been the drivers for tackling a couple of low-head weirs, on Eshton Beck (for the Upper Aire Project) and on Thornton Beck (completed as part of TROUT). And then there was the behemoth of Scotton Weir (funded by the Open Rivers Programme) connecting 18km of mainstem River Nidd and ~35km including key tributaries.
However, rivers should connect laterally with the floodplain and, to varying degrees, vertically with the groundwater. It’s a lateral connection of the Aire that we’ll be working on just south of Airton in an exciting new venture supported by the landowner.
Like so many hundreds of miles of Dales’ rivers, the channel south of Airton has been moved historically, most often to create more manageable blocks of (drained) land for farming in the valley, or ‘head’ for mills. And then it has been shackled using the material dug out of the artificial channel, effectively set in aspic so it cannot meander back across fields, near barns or away from bridges. Ghostly depressions on either side of the extant channel hint at a former, freer course, dynamic and meandering through space and time…. until humans came along!
Whilst it would be truly wonderful to unleash the Aire again, the constraints of a modern landscape – roads, bridges, footpaths, productive farmland, and fragmented ownership with different aspirations – mean that we can rarely fully restore a river…. but we can make things better.
Funded by the Yorkshire Water Biodiversity Enhancement programme, the local branch of Salmon & Trout Conservation, and the Upper Aire Project, there are several aspects to the proposed work to increase lateral connectivity. The overarching aim is to improve the habitat within the channel and across the floodplain for biodiversity, natural flood management and carbon sequestration.
- The formalised track / embankment running parallel to the channel on the true left bank (looking downstream) comprises boulder and cobble extracted from the river. Flower-rich turf will be set-aside where possible and stone sifted from soil to lower the bank before repositioning the turf. Where palaeochannels intersect with the extant channel, the level may be lowered further to encourage better connection. Hence, the intention is not to change / return the course of the river to historic paths but to allow floodwater to get out onto the floodplain more easily as the river rises during / following rainfall.
- Currently, erosive power is retained within the extant channel during spate flow for a considerable period, stripping out finer gravel and maintaining a barren, trapezoidal and consistently proportioned channel cross-section dominated by boulder and cobble. By improving lateral connectivity, the erosive power is dissipated more quickly across the floodplain allowing for retention of finer gravel in the channel.
- Boulder and cobble from the bank lowering will be returned to the channel in appropriate locations to diversify the channel cross-section and encourage further development of deposition bars. Excess soil will be moved away from the channel to create mounds of drier habitat via natural regeneration (hence increasing biodiversity) adjacent to drystone walls and protecting the walls from peak flood flow.
- Fencing will control a low density of rare-breed cattle, used primarily for conservation grazing to maintain the floral diversity of the wet(ter) meadow. It will also help reduce disturbance to ground-nesting & roosting birds from the Pennine Way which passes through the field to the east.
- A small number of native, local provenance trees will be planted along the bank edge to provide much needed shade in years to come, as well as providing habitat, leaf litter, and improving bank resilience via the root network.
While managed as a stand-alone project, it links longitudinally and laterally to many others in the immediate locality. Within a 2‑kiometre radius, the Upper Aire Project has facilitated the removal of Newfield Bridge weir (downstream), planted 4km of new hedging and ~1ha of trees, created 3 leaky ponds to slow-the-flow, and soil health has been improved over 53ha via mechanical aeration. Little pieces of a jigsaw, falling into place…