Glenmacnass Waterfall – an 80m cascade

Overview

Glenmacnass Waterfall drops 80 metres in three staggered steps at the head of the Glenmacnass Valley, in the Wicklow Mountains, north of Laragh. It’s a wide strip of silver more than a thundering plunge. After a couple of days of rain it fills out and earns the stop; in a dry spell it’s a trickle over grey rock. The Old Military Road follows the valley towards Sally Gap, and the drive is a good part of the reason to come.

The water flows over smooth grey porphyritic granite, part of the Lugnaquilla pluton in the Leinster Granite Batholith, and darker schist of the Maulin Formation shows further down the valley on both sides. The valley itself is a textbook glaciated U-shape, with a moraine roughly halfway between the falls and Laragh marking where the ice front once stalled.

The name and the rock

The Irish name, Gleann Log an Easa, means “the glen of the hollow of the waterfall.” The Geological Survey of Ireland describes the valley as a fine example of a glaciated U-shaped trough, with over-steepened sides and a flat floor, cut when ice sheets ground through here during the last glaciation.

On the mountain road, and the safety notice

Glenmacnass sits beside a fast, narrow mountain road, so the way you look at the falls matters as much as the falls themselves.

• Park only in designated parking and keep the road and any entrances clear. Do not stop on the carriageway or on verges.
• Stay behind the barriers. Do not climb the fence or wall at the top; the drop is severe.
• Keep off the river and its banks. The steep slope and wet rock around the falls are not suitable for scrambling. Do not pick your way down the wet river stones to reach the base, where the rock is slick and the current strong.
• Leave nothing visible in the car and carry no naked flames in dry spells.

Keep children and dogs close, and take care on any stretch of the road where there is no pavement.

Walking and wildlife

For a walk, the national park publishes marked routes at Glendalough, a short drive south, where the paths are signed and the footing is made for walkers. If you are heading for the Lough Tay area, choose Coillte’s Ballinastoe Wood and follow marked paths away from private shore access.

Redstarts, meadow pipits and buzzards are about the valley; red deer graze the higher slopes, and otters and wild trout are in the river below.

Getting there

By car

From Dublin, take the M50 to the N11 south, then the R115 (Old Military Road) towards Roundwood. The drive is half the point, winding over sheep-grazed uplands and peat bog. The road was built between 1801 and 1809 so British forces could patrol the mountains after the 1798 rebellion. Use only designated parking at the falls, and expect it to be busy on fine weekends.

Public transport

Limited, given how remote this is. Check the current St. Kevin’s Bus timetable for services from Dublin to Glendalough, from where you would need a taxi. Rail services on the Dublin–Rosslare line stop at Rathdrum, which is a taxi ride away. The road is not one for casual cyclists or walkers.

Nearby

• Sally Gap – the mountain crossroads at the top of the Old Military Road.
• Glendalough – St Kevin’s monastic valley, with its round tower and marked walking trails.
• Avoca Handweaving Mill – a working woollen mill down in the Avoca Valley.

Practical information

Come after rain and go early, and keep your view of the water to the safe side of the barriers.