23 July 2021
Benbrack: another peat landslide in Ireland
Posted by Dave Petley
Benbrack: another peat landslide in Ireland
Over the last few years I have blogged about peat landslides in Ireland on a number of occasions. Peat landslides are particularly interesting as they tend to have a long run out and they are extremely environmentally destructive, both in the source area (where the peat can take decades or more to regenerate) and downstream, where the peat can be a terrible pollutant. And of course peat is a key (and often degrading) carbon store; losing more is bad.
The newspaper The Anglo-Celt has a story about yet another peat landslide, this time at Benbrack in West Cavan, Republic of Ireland. The location is about 54.152, -7.852. This is the topography from Google Earth:-
Google Earth image of the topography of Benbrack in Ireland, the site of a new peat landslide.
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The landslide apparently occurred on 4 July 2021 during heavy rainfall. The landslide was photographed by a trekking enthusiast called Kevin Dockery:-
The peat landslide at Benbrack in Ireland. Image by Kevin Dockery via The Anglo-Celt.
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The landslide is also visible on the Planet Labs imagery of the area:-
Satellite image of the peat landslide at Benbrack in Ireland. Image copyright Planet Labs, used with permission, captured on 17 July 2021. Note the scale bar. The crown of the landslide is towards the south – it moved towards the northwest.
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Based on this image the landslide is about 600 m long. The newspaper article includes a description of the landslide:
…[T]he landslide started on the Benbrack summit plateau at a height of 470 metres above sea level, about 400m south west of Derrynananta.
“About six feet [2 m] deep of peat slipped away down the mountainside,” explained Kevin of the largest of three landslides in the area – two in Benbrack a smaller one on Cuilcagh.
“It was as if a big Hi-Mac scooped away all the peat down to the level where there were gravel and stones.
“There were massive chunks of peat gouged up – they wouldn’t fit into a car trailer they were that big. It just cascaded down the mountainside, it was extraordinary.”
This landslide does not appear to be associated with either forestry or wind farm development, as far as I can see.
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Reference
Planet Team (2021). Planet Application Program Interface: In Space for Life on Earth. San Francisco, CA. https://www.planet.com/
Dave Petley is the Vice-Chancellor of the University of Hull in the United Kingdom. His blog provides commentary and analysis of landslide events occurring worldwide, including the landslides themselves, latest research, and conferences and meetings.
Most, if not all, of the peat-covered uplands of Ireland are susceptible to failures of the peat cover. There is a particularly high density of such landslides in this small region, with this new slide being only 7 km S to SW from the 40+ recorded peat slides and bog slides on Cuilcagh Mountain, 14-15 km west of a large cluster on the summit plateau of Slieve Rushen, 16 km ESE from the large ‘Dawn of Hope’ bogflow that was reported here last summer, and there are other scientifically reported examples within 10 km.
The newspaper report at the link provided shows a photograph looking downslope from the upper source area. This shows a significant depth of soil to have been removed from beneath the peat. With no other information this looks like erosion as the failed peat accelerated down the steepening slope, but it is possible that the entire slide involved failure of the soil beneath the peat rather than failure of the peat or indeed the interface surface.
Does the peat transport cause carbon release? Or does it facilitate carbon capture by providing more space for future peat formation in the source area? Just curious about the competing mechanisms.
Hi all – Using the HazMapper Google Earth Engine application and Sentinel-2 imagery, it is apparent that there were 3 such events in the Benbrack, County Cavan area around July 4, 2021.
The one identified in this post is the middle one and the largest.
Here is the direct HazMapper URL: https://cmscheip.users.earthengine.app/view/hazmapper#lon=-7.852321854292139;lat=54.149500582537726;zoom=14;dataset=0;prewindow=0.5;postwindow=0.5;maxCloudCover=0;slopeThreshold=0;eventDate=20210704;