Allt Lorgy River Restoration Project

Restoring natural river processes and transforming habitat through a pioneering approach.

A tributary of the River Dulnain close to Carrbridge, the Allt Lorgy was historically straightened for agricultural purposes and was not functioning naturally, with poor ecological condition in places, and was causing flooding and maintenance problems for the landowner.

In 2012 an innovative ‘stage zero’ approach project, the first of its kind in Scotland, was trialled on a 880m reach. By removing artificial engineered constraints and encouraging natural river processes to return, the burn was allowed to restore itself to a more meandering channel with an abundance of physical features such as pools and riffles, which in turn provide valuable habitat for fish and other aquatic species. The over-grazed, bare flood plain was reconnected to the river and turned into thriving riparian woodland with wet areas, creating more new high quality habitat.

After over a decade the maturing project site is now celebrated as a pioneering success story in process-based river restoration and has inspired many other similar projects.

In 2020 the Allt Lorgy Project won the UK Rivers Prize (find out more here).

Project Delivery: What did we do?

The Allt Lorgy restoration project was conceived in 2011, with delivery of the river works taking only five days in 2012. Fencing and planting of the flood plain followed soon after.

Here are the main features of this project:

1. We started by lowering and removing embankments

We started by removing the higher embankments from this historically straightened section of the river and lowering them in other sections, giving the burn space to spread out and form meanders and, in high flows, spill out on to parts of the the flood plain, restoring a functional connection.

2. We then installed large woody structures

Boulders which had been placed to try to control flood flows were replaced with Large Woody Structures (LWS, felled trees with root plates attached) to naturally absorb energy from the water and prevent excess scour and erosion. Additional LWS were installed at strategic points in the channel encouraging more diverse flow patterns, leading to formation of natural river features and more diverse physical morphology in the channel. This in turn provides new and better habitat for aquatic life, including areas where fish and other wildlife can take refuge from flood flows and high water temperatures.

3. We re-introduced gravel upstream

Material excavated from the banks was re-introduced gradually at the upstream end of the site to be re-worked by the river into natural features.

4. Native woodland was returned to the flood plain

Deer fencing was erected around the wider site to keep browsing sheep, cows and deer out. To help kickstart the woodland, native broadleaf trees were planted at strategic locations. The results have been very positive, with the woodland now thriving and thousands of native trees self-seeding along the banks.

Image caption: Unfortunately,we don’t have many images of the site before our interventions were made. But as you can see from the image above, the burn was embanked on both sides, running straight through the landscape. Boulders had been added to the burn and due to grazing by deer, sheep and cows, there was no natural regeneration along either banks. Thankfully, you can see the mature seed source, which really helped to kick start the native woodland regeneration you’ll see in the images below.

What are the Benefits of this Project?

1. Natural river processes restored

The Allt Lorgy restoration project has successfully transformed a previously straightened and constrained watercourse into a flourishing dynamic system which is constantly evolving. By removing artificial barriers and enabling the water to carve a more natural, meandering path, the project has allowed the river to heal itself, creating an array of morphological features such as pools and riffles. These features play a critical role in diversifying the range of habitats available to aquatic and riparian species.

2. Enhanced and revitalised ecosystem

The new habitats created within the river, around the large woody structures, and on the banks provide excellent conditions for wildlife and support an increased diversity and abundance of river life. One of the highlights is the marked increase in breeding populations of salmon and trout. The now vibrant, wooded floodplain with areas of wetland and wet woodland is a much more diverse landscape than the previous heavily grazed pasture and is home to a much wider array of insect, bird, amphibian and mammal species.

3. Climate Change Mitigation and Adaptation

In response to climate change, the Allt Lorgy project has a role in both mitigation and adaptation. The restoration efforts will lead to improved carbon sequestration potential through the establishment of native woodland, re-wetting of soils and retention of fine sediment and organic matter in the catchment. Additionally, the creation of deeper pools and the shade provided by both bankside trees and the large woody structures within the river, have made the river and its inhabitants more resilient to increasing water temperature and more frequent flooding. The flood plain woodland and more complex channel form will play a part in slowing flood flows, reducing the need for maintenance by humans and contributing to controlling flood risk downstream.