Gareth Pedley – Wild Trout Trust
Back in June 2013 the Wild Trout Trust undertook an advisory visit for Glaisdale Angling Club on the River Esk, North Yorkshire. This was an interesting visit, identifying many of the common issues associated with livestock grazing and sandy soils on upland rivers leading to sedimentation. One specific issue was significant erosion on the outside of a particular sharp bend. This is exactly the type of issue that would have once been dealt with by hard engineering, often gabions or rip rap (rock armouring), for which there is already evidence of failed attempts. The Trust’s prescription here was to employ more sympathetic, natural bank protection measures that would actually enhance habitat in the area, rather than degrade it.
The use of brash revetment was considered, but the spatey nature of the river meant that there was a potential for further erosion from high water before any protection measures could be completed or take effect. So with this in mind, the recommendation was made to initially use a light touch, low cost approach that focused on fencing off a buffer strip along the bank to control the grazing (one of the main causal factors) and planting native tree species.
The tree and bank work was undertaken by 10 volunteers from Glaisdale Angling Club, in February 2014, coordinated by Simon Hirst of the North York Moors National Park Authority. In all, over 100 alder, 50 hazel and several hundred willow whips were planted, along with relocation of some of the overhanging bank turves onto bare areas of bank face.
As can be seen from the before and after photos from May 2015, fencing livestock away from the river bank has allowed large areas of the bank to become colonised by grass, the foliage and roots of which are already providing significant protection. The saplings and willow whips are now also well-established; the tree roots which will penetrate deeper into the ground and provide additional protection. If the fence is maintained, and livestock continue to be excluded, it can be expected that over the upcoming seasons the more stable bank will facilitate the colonisation of other herbaceous vegetation. This will increase the diversity of root structure within the bank and provide even greater consolidation. The roughness they provide will also aid natural colonisation with local trees and plants by trapping seeds and other propagules (agent of reproduction).
Although the bank is still not completely stabilised yet, and the technique is always initially susceptible to failure in very high flows, it is relatively low cost and provides a great demonstration of how removing the livestock grazing pressure can reduce erosion and stabilise river banks. If major floods do not destabilise the banks they will continue to consolidate and stabilise to natural levels. If major floods do cause further erosion in the future, there may be a case for undertaking a more formal brash revetment as well.
U P D A T E – July 2017
Simon Hirst – River Esk Project Officer
Kate (Catchment Partnership Officer) and I recently revisited the site with the Glaisdale Angling Club to assess the bank stabilisation work undertaken on this section of the River Esk back in February 2014. Three years later, the young alder, hazel and willow trees are flourishing, and woodrush has also successfully colonised the site naturally.
We’re planning to carry out further work in winter 2019, which will involve hazel and willow laying, like you would with a hedge to provide horizontal structure. This work will further protect and stabilise the bank, and some of the stems will also be laid into the channel to provide in-channel cover for fish.