15 March 2022
A drone video of the B4069 Lyneham landslide
On 25 February I blogged about the Lyneham landslide, a substantial failure on the B4069 road at Dauntsey Banks in Wiltshire, in southern England. With thanks to Stuart Lewis, who highlighted in a comment to that original post that a video has now been posted to Youtube that provides drone footage of the landslide:-
The video, which was collected on 8 March 2022, provides both aerial views and static shots of this most interesting landslide. In my original post I noted that there appears to have been construction activity in the field directly upslope of the road. The video provides clarification on this. The image below is a still from the video – it is most interesting:-
Here is another view of the site:-
I think there are a few things to note here. First, the landslide has extended most of the way through this field, with the largest rear scarp area being located adjacent to the pad on which the new buildings are being constructed. Second, the failed section of road corresponds very closely to the eastern boundaries of the field in which construction was being undertaken. This is particularly evident in the first of the two images above. Third, it appears that although building construction has occurred in only a part of this field, it appears that the surface cover throughout has been changed. This is the field in 2019, from Google Earth:-
I am speculating here, but has the field been regraded (note the scarps downslope of the tracks in the second image)?
Of course, I cannot provide a link between the activities in this field and the reactivation of the landslide – that could only be established through a proper site investigation. I am sure that this is being undertaken. There are other possible causes. But it is certainly a line of enquiry that is worthy of deeper examination.
As I noted in my first post, this is an area that shows clear signs of previous landslide activity, and the failure appears to me to be a reactivation. This highlights why it is important to get input from an engineering geomorphologist before undertaking works such as this in these areas.