Allt Lorgy Restoration
cbec applied a full ‘process restoration’ strategy on a tributary of the River Dulnain, with the aim of reinstating dynamic geomorphic and ecological processes.
We identified the dominant constraints to natural process and implemented associated measures to reduce these. This involved the addition of large wood and gravel augmentation and the removal of flood embankments. Assessments of sediment transport processes guided the optimal locations for gravel augmentation so that the introduced material could be redistributed through the site to create new spawning habitat. High flow events subsequent to construction have already begun a trajectory towards the desired physical and ecological state. This has included the development of alluvial (gravel) bar features, greater channel heterogeneity, increased lateral geomorphic process (increased sinuosity) and greater channel-floodplain connectivity. The development of gravel-bar features has been associated with increased spawning habitat that has already been utilized by sea trout and Atlantic salmon. We will monitor the site over the next few years to quantitatively determine how the channel adjusts to the restoration works. Three weeks after completion, a large flood event tested the designs and confirmed that the models and the physical restoration works were completed as intended.