5 April 2022
Mount Bolu: an interesting case study of a tunnel portal landslide in Turkey
On 2 April 2022 heavy rainfall triggered an economically significant landslide in at Mount Bolu in Turkey. The landslide occurred after a spell of rainfall that in places has fallen onto snow. This is a recipe for landslides in upland areas.
The Mount Bolu Tunnel landslide is interesting though. It has blocked four lanes of the D-100 road, a critical east-west connection across the north of Turkey. This is an image of the landslide:-
This is an alternative view that shows the landslide source more clearly, as well as some of the debris blocking the carriageway:-
The site of the tunnel is at 40.7578, 31.4504. It is clearly visible on Google Earth. The tunnel was completed in 2007.
There are some very interesting images online of the site of this landslide prior to the 2 April 2022 landslide. This image for example shows the tunnel portals and the slope above:-
The archive of Google Earth imagery does not seem to indicate that further works have been undertaken to stabilise this slope, although of course satellite/aerial imagery has limitations. But on first inspection this is an ugly slope to be located above a tunnel portal on such an important highway, especially in a region that is seismically active.
The debris has taken 44 hours to clear, but the road has now reopened. The images suggest that further works will be needed on the slopes at this site, both in the scar of the 2 April 2022 landslide and on the slope to the left of it (as seen in the images), which appears to be another potential landslide site.
Northern Turkey has been suffering from a wave of landslides in recent days:-
Rapid snow melts have triggered more than 400 landslides in northern Turkey (in Bolu, Bartin, Samsun, Ordu, and Trabzon) in the last week. This foehn effect looks like will continue along the next week. Continue the landslide watch. Video credit @ihacomtr pic.twitter.com/oUfexjgOJH
— Tolga Gorum (@TolgaGorum) April 3, 2022