Recent debris flows in the Lairig Ghru are made obvious by the presence of fresh granite clasts in the debris. Most are triggered by intense rain storms (Luckman, 1992). The debris cover at the head of the gulley becomes unstable and then flows as a slurry down the chute to form a lobe of debris at the foot of the slope. Over 70 debris flows were mobilised in the Ghru between 1970 and 1980 (Innes, 1983). An intense rainstorm in summer 2002 gave a fine debris flow below Aladdin's Couloir. An excellent section through a sequence of late Holocene debris flows is found in Glen Feshie.
Debris flows
Definition: the rapid flow of unconsolidated material downslope
Recent debris flow in the Slochd Bheag, Ben Avon.
The source lies at the head of the gulley and a debris cone is accumulating at
its foot. Note the levées beside the middle gulley, where
friction has slowed the torrent at the margin of the channel and prompted
deposition. The movement of a slurry charged with rocks and finer debris is
indicated clearly by the tongues of coarse debris in the foreground.