The ongoing landslide at St Lawrence on the Isle of Wight. – GWC Mag

by gwcmag
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The Landslide Blog is written by Dave Petley, who is widely recognized as a world leader in the study and management of landslides.

Image of a landslide partially covered with a transparent sand-colored overlay and the words “The Landslide Blog,” centered, in white

The extraordinary spell of wet weather continues to have a major impact across the United Kingdom, with landslides occurring in many places. The rail network is being significantly disrupted by earthworks failures, for example.

On the Isle of Wight, a number of landslides have developed over the winter, with the latest being the large failure at St Lawrence to the west of Ventnor in the Undercliff. Over the last two days, a couple of additional pieces of information have emerged that helps to understand the landslide. A community website, the Island Echo, has published a set of drone images of damage caused by the landslide, of which this photograph is one:-

Landslide damage at St Lawrence on the Isle of Wight
Landslide damage at St Lawrence on the Isle of Wight. Credit: Island Echo.

Note the large tension cracks across the gardens of the houses – close inspection of the images shows that this damage extends to the upslope side of the houses. Another drone image, looking directly onto the landslide, shows the tension cracks, but also picks up serious damage to a property downslope:-

A view of landslide damage at St Lawrence on the Isle of Wight.
A view of landslide damage at St Lawrence on the Isle of Wight. Credit: Island Echo

The damage to this lower house (which I believe is located at [50.5826, -1.2572], and the land around it, is highlighted in a video that has been posted to Youtube by Allen Wood:-

YouTube video

The damage to this property is severe already – the news report indicates it is a total loss – and there is a huge amount of ground deformation too:-

Damage to a residential property caused by the landslide at St Lawrence.
Damage to a residential property caused by the landslide at St Lawrence. Credit: Still from a video by Allen Wood.

As I noted above, the key driver has been exceptional rainfall for the United Kingdom over a prolonged period. Dave Throup has a really interesting pair of tweets that illustrate this point:-

This continues apace in the southern portion of the country, as the tweeted chart below shows:-

Detailed monitoring at the Ventnor landslide (see Carey, Moore and Petley 2014, and a blog post that I made about that paper), just to the east of this one, suggest that the landslide movement lags rainfall by some months. Thus, with the high rainfall totals continuing, further landslide movement might be expected in this area.

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

Text © 2023. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

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