How to destablize a hill in quicktime: Nursery Gaon landslides, (Kalimpong) 07Jul2020

I had visited Nursery Gaon along with GSI Geologist Debashish Bhattacharya in Dec 2012 and blogged about it. It lies below the 7/8th mile area of Kalimpong and several landslides there were active even then. Some picture posts of our visit in 2012 from the STH blog are below:

Subsequently on 01Jul2015, following heavy rainfall, a landslide occurred again at Nursery Gaon and an entire family perished. Their bodies could never be traced.

• I am very familiar with the area which lies on the western face of Kalimpong and as such is steep and mostly rocky. Compared to the eastern face, this region has sparse population but at the crest (the 8th mile area) there is a large urban build up with several prominent schools, flower nurseries and the road (State Highway -SH12) linking Kalimpong to Teesta bazar passes thru this region.

• Kalimpong has long needed a by pass road since the SH12 passes thru town and traffic snarls are increasingly becoming impossible esp when large military vehicles have to pass thru narrow areas. To obviate routing thru the congested town area, a by pass road circumventing the urban cluster was planned. This road which was to start at 7th mile, pass below the 8th mile area and terminate somewhere in Bhalukhop avoiding the entire town area.

• The by pass road was inaugurated in 2009 (to the best of my knowledge) and rather coincidentally my first record of a landslide in the region is also of Aug 2009.

• Since then I have visited the by pass area many times, to check the increasing areas of instability along the road.
• On 07Jul2020, following heavy rains, there were reports of landslides in the area. I visited the area on 10Jul2020 and this is my assessment:

Images from my survey in the area are place below:

Size of slide is approx 60m in length

The length of this subsidence is around 30-40m

RAINFALL ON 06Jul2020 : 109mm

Having talked to affected people of the area:
1. It is well known that roads interfere with the natural drainage of a mountain and therefore are a major cause of landslides. In the case of the above landslides, this is very evident. Whereas there was little instability in this region before 2009, the incidents of landslides have increased sharply over the years.
2. This was very evident even in 2012, when I visited the area and made a pointed remark that this area would be susceptible to slope failures due to poor drainage (see first slide).
3. Sure enough, on 01JUL2015 we had a fatal landslide in the area.
4. Unfortunately even after that, nothing has improved. Merely loading the area with more concrete, stone and sand is NOT the solution and perhaps the engineers will have to incorporate some innovative ideas on how to manage the water and improve drainage.
5. High time we think seriously about how to control the instability instead of how to make money from it.

Praful Rao
Kalimpong district
Darjeeling-Sikkim Himalaya