25 February 2022

Lyneham – an interesting landslide from the south of England

Posted by Dave Petley

Lyneham – an interesting landslide from the south of England

Yesterday the BBC reported on another serious landslide triggered by the heavy rainfall that fell across the UK last week.  This landslide has caused very significant damage to the B6049 road near to the village of Lyneham in Wiltshire.  The location is 51.517, -1.991.  The BBC has this image of the aftermath of the landslide:-

Damage to the B4069 in Lyneham, Wiltshire. Image from the BBC.

Landslide damage to the B4069 in Lyneham, Wiltshire. Image from the BBC.

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It is clear that there has been very substantial vertical movement on the slope.  Interestingly, a Google StreetView image of the road suggests that it was undergoing considerable distress back in October 2021:-

Google StreetView of a section of the B6049 near to Lyneham, showing extensive cracking in the road.

Google StreetView of a section of the B6049 near to Lyneham, showing extensive cracking in the road.

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This crack appears to indicate extension, which is consistent with the deformation observed in the failure last week.

Google Earth has good imagery of the site.  This image was collected in April 2021:-

Google Earth image of the site of the landslide at Lyneham in southern England.

Google Earth image of the site of the landslide at Lyneham in southern England. Note the relict solifluction feature in the field downslope of the road.

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In the field downslope of the road (nearer to the camera) there is a clear large, shallow landslide lobe.  There is a further lobe to the right of the image, emerging from the same morphological feature.  I would interpret this as probable ancient solifluction landslide – an active layer detachment – left over from the period when this area was affected by permafrost conditions during Pleistocene “Ice Age”.  These features are common in southern Britain. Note also that upslope of the road there appear to be some features that could be tension cracks in the field.

There are similar lobes in some of the other fields too.

So the most likely explanation for the landslide near to Lyneham is that it is a reactivation of a pre-existing failure, probably a solifluction landslide, caused by the exceptional rainfall that we are now experiencing.  Of course a detailed site investigation is needed to verify this initial hypothesis.

It will also be interesting to find out whether this is simply the results of increased rainfall or whether some other change has occurred in the area, such as a modification to the drainage. Are there signs of some construction activity in the field in the top left corner, for example?  Without a detailed investigation it is impossible to know if this could have been a factor.


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