Walk on the Wild Side: Across moorland to Loch Oss

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This week it is time for something different; not a climb to a hill but a moorland walk to a secretive loch beneath a horseshoe of crags.

Beinn Dubhchraig and Ben Oss, both clearly identifiable from the north end of Loch Lomond, are usually climbed as a pair, perhaps as part of the four-Munro Ben Lui traverse. They are invariably tackled from Dalrigh to the north-east, via the beautiful ancient pinewood of Coille Coire Chuilc, one of the few remnants of the old Caledonian Forest.

Higher up, the Munro path can be muddy and slippy and, but for the delights of Coille Coire Chuilc, not a good start to the day. The route leads to a plateau, west of which is the 779m Bealach Buidhe separating Beinn Dubhchraig from Ben Oss.

These peaks are the two arms of a craggy south-facing amphitheatre, Coire Garbh, the rough corrie, and nestling some 150m below the bealach is Loch Oss, very seldom visited by hillwalkers. Draining south-eastwards over an expanse of gently sloping moorland via Fionn Ghleann towards Glen Falloch, the waters of the loch change character on their journey, reflected in a series of name changes… Allt Oss, Sput Ban and finally Allt Fionn Ghlinne.

A four-mile varied approach from Glen Falloch via Fionn Ghleann, a longer and seldom-used moorland route, thus gives direct access to Loch Oss and is the walk described below. Going in the middle of a dry spell is recommended. Although no hill climb is involved, nevertheless with a near sea-level start it is a 600m ascent to the loch and some of the four-mile distance is over rough terrain. Accordingly, allow some five hours for the there and back journey.

You will need Ordnance Survey map 50, Glen Orchy & Loch Etive.

Use the signposted Falls of Falloch car park on the south side of the A82, map ref 334208; a secluded spot so take care with car security. A short distance to the west, a track goes on the east side of the Allt Fionn Ghlinne. Just before reaching the railway line, take the less obvious branch on the right that leads to an underpass, then on to open country.

The track peters out and it is then best to follow the east bank of the river all the way. The first mile, rough and wet in places, is not made for fast walking and there is little in the way of a path… but do persevere. Once past a waterfall, and by now with the A82 lost to sight and sound, the second mile in Fionn Ghleann by the meandering water is altogether more attractive, with animal tracks easing the way. The appearance of Beinn Dubhchraig's peak may quicken the pace as will the sight of the obvious and well-named Sput Ban, where the white waters of the Allt Oss tumble eastwards. In a dry spell it is fun to clamber by the wide strip of exposed rock. The last mile by the Allt Oss is through mysterious moorland with the Oss/Dubhchraig crags towering ahead. It is still preferable to stay with the east bank as the Allt Oss struggles to escape from the loch. Suddenly the loch appears.

With good views looking south down Loch Lomond, do linger to appreciate the rough beauty of the crags that half surround the peaceful waters.

But what is the meaning of "Oss"? Ben Oss may mean hill of the elk, once common in these parts but extinct for over 700 years. Another explanation is that the name derives from os, the outlet of a stream. There is a lochan to the south of Creag Dhubh a' Bhealaich, but it seems unlikely that this minor feature could give rise to the name. There is of course the much larger Loch Oss itself, but the elk explanation seems more likely … and more primeval if visiting the loch on a very misty day.

After my June visit, a lovely warm and dry outing and seeing not a soul all day, I described to Rhona my delight on visiting Loch Oss. I suggested that very few hillwalkers had ever visited the loch and indeed I personally knew of none.

I should have known better.

"But I have been there, on a traverse from Glen Falloch to Strath Fillan" was the intrepid Rhona's response. Incidentally. I know of only one Munro round completion on Ben Oss, that by Rhona in November 2000... her third round.Factfile

Map Ordnance Survey map 50, Glen Orchy & Loch Etive

Distance 8 miles

Height 600m

Terrain Mostly pathless and rough and wet in places

Start point Falls of Falloch car park, south side of the A82, map ref 334208

Time 5 hours

Nearest village Ardlui

Nearest refreshment spot

Inverarnan Inn