A section of riverbank in Co Tyrone which was eroded by flash flooding has been stabilised as part of a wider habitat enhancement project being progressed by the Loughs Agency.
Flood waters in the Owenkillew River had stripped the 160m riverbank area of vegetation, and trees became unstable resulting in subsidence and suspended solids entering the river at Beltrim Estate in Gortin.
Loughs Agency chief executive Sharon McMahon said the site was identified as needing support to improve water quality for the benefit of downstream salmonid spawning sites.
“Managing and supporting a sustainable wild fishery is a careful balance of conservation, protection and letting nature take its course,” she explained.
The Loughs Agency engaged with the landowner who had recently installed fencing to protect the riverbank from livestock access.
From top: before, during and after the riverbank enhancement works on the Owenkillew River in Co Tyrone | Credit: Loughs Agency
Larch timber poles were then driven into the edge of the river to reinforce the bank, while layers of horizontal poles were fixed to protect the base of the riverbank. Brash was installed behind the poles to help catch silt and debris and naturalise the bank.
The area behind the revetment was planted with native broadleaf trees including hazel, oak and alder. Willow was also planted tight into the riverbank so that the root structure would help stabilise the bank, further reducing erosion.
While the riverbank has naturalised with trees and plants becoming established during the summer, the invasive Himalayan balsam plant has unfortunately also established itself. The agency says it hopes to reduce coverage on this non-native species by removing stems before it goes to seed next year.
Seamus Cullinan, fishery inspector at the Loughs Agency, said: “It is important to understand the cause of riverbank erosion and design the most appropriate solution to mitigate against it. This type of green engineering is sustainable and effective at providing long-term stabilisation and benefits for the fishery.”
Loughs Agency has used green engineering solutions in other sites in Northern Ireland's Foyle catchment, where persistent water flow and floods are responsible for removing bank material, causing erosion and subsidence.
The Owenkillew, Camowen, Glenelly and Finn rivers are among several river enhancement projects scheduled for this year.
