Overview:
The 10 December 2023 landslide that occurred in the south of England has led to 20 houses being evacuated.
The Landslide Blog is written by Dave Petley, who is widely recognized as a world leader in the study and management of landslides.
On 10 December 2023 a large landslide occurred at Bonchurch on the Isle of Wight in the south of England. This coastal failure occurred after a long period of heavy rainfall. There are two very good local news articles about this failure – first, the Island Echo has an excellent piece that includes photographs and a video of the aftermath of the landslide. Second, On the Wight has a more reflective analysis, including quotes from the local authority leaders responsible for slope safety.
The drone footage of the landslide is on Youtube, and should be visible below:-
The footage shows that this large failure has threatened a number of buildings and one of the key roads into Bonchurch and the larger town of Ventnor. The still from the video below gives a sense of the overall scale of the landslide, and the proximity to local houses and a café (the white building at the crown of the landslide):-
No properties have been destroyed, but 20 have been evacuated and the road is closed.
That a landslide should occur at this point is not a surprise. Indeed, this area is called “Upper Landslip” on the Ordnance Survey map. The location is at [50.60609, -1.17846]. This is Google Earth perspective view of the site:-
Note the name of the carpark in the upper right corner of the image.
Bonchurch lies at the eastern end of the Ventnor landslide complex, the largest urban landslide site in Western Europe. This complex was studied in detail by my PhD student, Dr Jon Carey, who is now the University of Birmingham. His PhD thesis is available on the University of Durham website.
There is an intriguing section of the On the Wight report from yesterday:-
Only one road in and out?
In a separate incident at the Graben (where Ocean View Road meets Newport Road), Natasha [Dix, from the Isle of Wight Council] said access between lower and Upper Ventnor will close later this afternoon.A new dip in the road has been reported (Southern Water report a damaged sewer) and although this is an ongoing issue, it will be closed and then assessed by Island Roads. The road will then remain closed until it’s deemed safe to reopen.
That will leave just Whitwell Road as the only access to and from Ventnor.
Source: https://onthewight.com/only-one-road-in-an-out-of-ventnor-following-largest-landslide-in-20-years/
I discussed the Ventnor Graben in a post about a paper that we wrote about the movement of the Ventnor landslide complex (Carey et al. 2014). The Graben is an extensional structure of the large landslide complex that sits under the town. This landslide moves during periods of prolonged wet weather when the groundwater level becomes high. Displacement rates are typically slow, so the risks to life and property are low, but this does seem to indicate a wider pattern of movement in the Ventnor landslide complex at the moment.
Reference
Carey, J.M., Moore, R. and Petley, D.N. 2014. Patterns of movement in the Ventnor landslide complex, Isle of Wight, southern England. Landslides. doi: http://dx.doi.org/10.1007/s10346-014-0538-1