3 June 2021
Not all slope failures are large
Inevitably, on this blog I tend to cover larger landslides most of the time. Large landslides have a greater propensity to cause loss and to disrupt, and of course they are also more newsworthy and they are frequently photogenic. However, this gives a very misleading impression of slope failures, the vast majority of which are small. Nonetheless, even these less impressive landslides can have substantial impacts.
Whilst walking around my home city of Sheffield in the current spell of warm, sunny early summer weather, I have spotted a series of smaller but interesting slope failures. I thought it would be interesting to highlight two of them.
The Sheffield and Tinsley Canal is a 6 km long waterway constructed in 1819 to link the city of Sheffield with the navigable parts of the River Don, allowing goods and people to be transported into and out of the city. Its greatest claim to fame is that the it is the location of part of the opening scenes of the film The Full Monty (although it looks considerably better than that now!).
Today the canal is navigable by pleasure craft, and the towpath forms a walking and cycle route. The image below shows a small slope failure that has occurred in a section of the canal:
As the image shows, about a 15 m section of the canal bank has collapsed. In the foreground a further section is failing. In other sections of the canal, failures are developing but have not collapsed:-
The stone blocks have moved towards the canal by about 50 cm, and the fill has subsided by about 30 cm. In this case failure, when it occurs, will substantially disrupt the towpath. There are other sections in a similar state.
None of these slope failures are large or dramatic, but they have the potential to close the towpath.
The second case lies on my walk to work. Here, at the top of a steep bank, a retaining wall has recently been constructed to create a pathway for pedestrians. It appears that this wall, which is about 50 cm high, has also started to fail and to move downslope. The owners of the site have employed a novel method to provide short term increased stability:
Securing a slope using cargo straps tied to the trees is not an approach that I have seen before. Again, this is small incipient slope failure, but one that is causing disruption.