The Landslide Blog is written by Dave Petley, who is widely recognized as a world leader in the study and management of landslides.
Alongside many other places, Chile has been experiencing exceptional rainfall in recent days, causing flooding and landslides. A particularly interesting event has occurred the Socavón Cochoa area of the coastal town of Viña del Mar. There is a range of videos and images of this event posted to Twitter, such as this helicopter footage and ground level video:-
The image below of this large erosive feature is taken from the helicopter video:-
News reports (in Spanish) link this event directly to heavy rainfall that was associated with a weather front. The apartment bock has been evacuated.
To understand what has happened, it is interesting to look at the Google Earth image of the site, which is located at: [-32.94635, -71.54897]:-
There are several things to note here. First, it is obvious that the entire site is constructed on a partially vegetated sand dune. The erosive feature shows the thickness of the dune, with sand being present to the base of the new channel. Second, the erosion has occurred at the end of the road that slopes down the dune, past the apartments. This road will inevitably collect a large volume of rainwater, which will be channeled to the lowest point. Thus, on a dune, management of the drainage at this point, and downslope, is critical.
Archive Google Earth imagery – this is from 2008 – appears to show that some sort of water management structure was in place:-
This site is visible on Google Street View, from 2014:-
It appears that the drainage at the end of the road consisted of a large pipe that transported the water to the shoreline.
Interestingly, there is another image of the site on Twitter, which appears to show the pipe in a very poor condition but with the retaining wall at the top of the slope intact (top right image):-
The pipe appears to have been broken before the recent rainfall event, and erosion had started. Thus, my working hypothesis to this event was that it was caused by headward erosion of the sand in the dune induced by heavy rainfall. If this is correct, then it appears to be related to maintenance of the pipe.
The key question now is going to be who was responsible for the maintenance of the pipe. Fixing this area of erosion is going to be complex and expensive, and it is urgent as further heavy rainfall is likely to bring further erosion.