Scriddan

AUCHUIRN, in the Shire of Ross: and in the Parish of Kintail. This is now a Farm in Glenelchaig, but was once a populous Town, which, in 1745, was rendered uninhabitable by an awful Scriddan or Mountain Torrent, and has since been converted into a grazing District.

Source: wiktionary

"The showers here are much more violent than any in the Lowlands," said Bonclair. "Not so bad as they are farther in the hills," said the minister. "There they are so destructive, that I have seen entire clachans ruined, and whole fields covered by a scridan." "What is a scridan?" inquired Mr Bonclair. "Why, sir," replied the minister, "when the rain, falling on the side of a hill, tears the surface, and precipitates a large quantity of stones and gravel into the plain below, we call that a scridan."

Source: wiktionary

... Scriddans are also frequent in the wilds of Sutherland and Caithness.

Source: wiktionary

She lay in a deep chasm of the wild rocks, at the base of a steep mountain, the sides of which had been bared and rent by the scriddans of a thousand years - for so the natives term those water-torrents which at times hurl down gravel and massive stones, in vast heaps, to desolate the fields, the shore, or whatever may lie at the foot of these rugged [peaks].

Source: wiktionary