19 February 2015
Paglajhora: another progressive road failure video
Posted by Dave Petley
Paglajhora landslide video
There is an interesting video on Youtube from Paglajhora showing the collapse of a section of road:
Whilst this is not a new video (the accompanying text indicates that it occurred on 15th July 2010), I don’t think I’ve seen it before. The landslide apparently occurred at Paglajhora, on the Hill Cart Road connecting Siliguri and Kurseong in Darjeeling, northern India.
Paglajhora is described in a paper (Sarkar 2011) that is available online (NB PDF). This section of the Shiv Khola river is, according to Sarkar (2011):
“notorious for its slump/subsidence history that was initiated during the 1950 landslips in Darjeeling Hills…Since 1980, the incidences of slumping have become regular phenomenon, and by 1990 the Paglajhora slumps caused complete disruption of transportation and communication. The situation has deteriorated further in recent years”
The Paglajhora area is shown in the Google Earth image below; the yellow line is the Hill Cart Road:
The very extensive mass movement problem on this section of road is very clear, and indeed a closer view gives a better perspective on the serious nature of the problem at Paglajhora:
Sarkar (2011) suggests that the landslide problem at Paglajhora is the result of very weak colluvial materials, the origin of which is attributed to much older and much larger landslides. The nature of these postulated landslides is intriguing and deserves further study. These deposits were then reactivated by low quality construction and maintenance of the road and railway line, with poor management of the slope continuing to play a major role in the problems. The image above, from April 2014, suggests that the problem is not going to get better soon without proper management, and indeed the inevitable retrogression of the crown of the landslide is going to threaten settlements upslope soon. Perhaps the most shocking aspect of this is a comparison with the Google Earth image from January 2003:
The deterioration of the stability of the site in 12 years is remarkable. The morphology of the slopes in the 2003 image above would ring alarm bells to any competent geomorphologist or engineering geologist, and with good slope management it should have been possible to prevent this slope problem from developing. But, now that the instability has been initiated it will be extremely difficult, and expensive, to stop.
Sarkar, S. 2011. Evolution of the Paglajhora slump valley in the Shiv Khola Basin, the Darjeeling Himalaya, India. Geographia Polonica, 84 (2), 117-126.