The Allt Lorgy river restoration project in the Scottish Highlands, which was designed by RSK company cbec in 2012, has won the 2020 UK River Prize for reach scale at the River Restoration Centre annual conference. cbec was responsible for the investigation and geomorphic design of this major restoration project, which was the first of its kind in Britain.
The Allt Lorgy is a typical upland spate burn that was significantly managed for agricultural purposes in the late 1980s. As a result, it included artificial embankments, rock bank revetments and in-channel boulder grade control. The restoration project aimed to restore the morphology and associated habitats of a 1-km section of the river and its adjoining floodplain by removing artificial constraints. The aim was to re-establish the fundamental physical processes that drive the evolution of the river’s form and the associated benefits for instream, riparian and floodplain ecology.
“As the principal designer we were employed to do the geomorphic design for the site in 2012,” explains cbec Managing Director Hamish Moir. “It was one of the first ‘assisted recovery’ or ‘Stage 0’ projects completed in the UK.
“We took a process-based approach following an assisted recovery philosophy. We tried to remove the constraints to the natural river process by removing embankments and rock bank protection, and implementing large wood structures at appropriate locations to really kick-start the geomorphic process. The sediment that we removed from the embankments had previously been dredged from the river, and we used that to resupply two locations on the site, thus kick-starting the natural sediment transport processes.
“We didn’t know how important this type of project was going to be, but it has turned into a really good case study for how restoration should perhaps be done in these types of river environments.”
This work has now resulted in a self-sustaining system; enhanced lateral channel migration has begun the natural recruitment of riparian trees into the watercourse, which further invigorates the dynamic change. Eight years later, and after several of high-flow events, significant evolution of the site has occurred. In effect, the ‘circle of restoration’ has been closed, thus providing a sustainably evolving river environment.
Before and after of the embankment and avulsed braided channels
The project team also included the Spey Fishery Board, the Cairngorm National Park Authority, SCOTLAND: The Big Picture, Scottish Natural Heritage and SEPA.
The UK River Prize celebrates the achievements of individuals and organisations working to improve rivers and catchments, and recognises the benefits to society of having a healthy natural environment. This year’s winner was announced at the River Restoration Centre annual conference on 9 September.
Martin Janes, Managing Director of the River Restoration Centre, commented, “The high standard of entries for this year’s UK River Prize has once again demonstrated the enthusiasm, passion and commitment of local partnerships, charities, volunteers and agencies, in working to restore the freshwater landscape for people and wildlife. On behalf of the judges, it is always a pleasure to read the detail of all the projects, and a real challenge to choose between them. I would like to thank all of this year’s applicants who submitted their excellent projects from across the UK.”
You can view all the 2020 finalists on the River Restoration Centre website.