How nature heals: a look at several landslides in Kalimpong

Massive landslide at Bhalukhop (Kalimpong district) on 29Jul2021, following 232mm rainfall in 13hrs. Nature has slowly healed this area over a 4 year period without any engineering mitigation measures being applied.

By no stretch of imagination am I an expert on landslides but having visited numerous landslides over the years and having observed the changes taking place, I believe that under the right circumstances and with time, nature has a remarkable way of healing landslides.
Here are case studies and photos of 3 landslides in and around Kalimpong:

14th mile landslide in Kalimpong

This is a really old landslide and 'a sinking zone' which existed more than 50 years ago. STH has covered this extensively in this blog in 2007 and in 2010

Drone image of 14th Mile landslide on 21Feb2025. The whole landslide area is now covered with trees

Drone image of 14th Mile landslide on 21Feb2025. The whole landslide area is now covered with trees

 

Massive Landslide at Bhalukhop (Kalimpong district) on 30Jul2021.

A 232mm rainfall over a 13hr period on 29/30July2021 triggered a massive  landslide in my village, Bhalukhop in Kalimpong; the incident has been covered in a STH blogpost here. I have placed a Google Earth image of the landslide path below:

The length of the slide from crown to toe was approx 1880 ft (measured on Google Earth).

Where the landslide started - at the crest near Deolo Hill.

The mid-section of the slide in Dec2021

Ms Minu Thapa,showing us the extent of devastation in her farm at the base of the landslide in Dec2021

In this Feb 2025 drone image; Ms Minu Thapa's home lies just above the road bend and the entire landslide affected area all the way to the crest is seen covered with vegetation and trees, 4 years after the terrible Jul2021 landslide.

Another drone image of the landslide affected area - showing no trace of the landslide after nature took over.

 

Dhajey, Bara Bhalukhop

As a native of this village, I'm deeply familiar with the landslide issues in our area. To address this problem, the local community employed a traditional mitigation method at Dhajey, which involved a three-step approach:

1. Water diversion: A concrete river training structure was built to channel water away from the landslide-prone area (see top photo).
2. Soil stabilization: Bamboo palisades were constructed to prevent soil erosion during rainfall, allowing pioneer species like mosses and lichens to take root. Under favorable conditions, grasses and small shrubs would emerge within a year, anchoring the soil and reducing erosion. Alternatively, jute matting or fiber could have been used to support the new vegetation (lower photo).
3. Long-term stabilization: Over several years, larger plants like bushes and shrubs would grow, holding the soil together and enabling deeper-rooted species like trees to develop, further binding the soil through nature's "soil nailing" process.

 

Drone image of this area on 21Feb2025 is shown below👇. The RED circle delineates the area where the bamboo check dams were 'planted'.

Drone image of landslide areas at Dhajey, Bara Bhalukhop👇

1 - A large landslide had taken place here several years ago, which  nature has apparently healed.

  2 - Area where locals applied tradtitional bamboo check dam mitigation measures which has stabilized the place at least for the past 2 monsoons.

 

Documentation of parts of the above report was supported by Royal Enfield, as part of their Social Mission Initiative

Praful Rao
SaveTheHills
savethehills@gmail.com
9475033744

The National Highway 10 (NH10 - Siliguri to Gangtok) maintenance problem (post GLOF) begins in Mar2024

NH10 and Likhu Bhir in 2017 & 2023

MoRTH website on NH10 reads as follows:
'The highway starting from Indo / Bangladesh Border connecting Fulbari Siliguri in the State of West Bengal connecting Sivok, Kalimpang near N.H-10 and terminating at Gangtok in the State of Sikkim'. 52kms of the highway is in Sikkim, the remaining 65.97kms being in W Bengal.
Further to our earlier report on National Highway 10 (NH10), the recent rains in our region caused landslides along parts of NH10 which resulted in road blockages and traffic jams and as such the Kalimpong District Administration has closed parts of NH10 for traffic as per the letter below:

 

 

Prolonged closure of NH10 dates
Road closures for several hours on NH10 due to landslips, erosion and rockfalls etc are commonplace and take place almost daily during the monsoons. Prolonged closure dates of the highway in the recent past are as follows:-
* In 2007 and 11Jun2010 at HaatiSurey, near Coronation bridge – blocked for a week.
* 26Jun-03Jul2015 due to landslide at SetiJhora (near TLDP IV)
* 14-15Jan 2016 due to landslide at BhoteyBhir (near Rangpo)
* 06Jul2019 for almost a week at Seti Jhora

Despite several alternate routes now being available (see map below), NH10 remains the shortest distance with the least gradient changes and is the quickest way to commute from Sikkim and Kalimpong to SIliguri and the plains of North Bengal - however, it may not be the safest route anymore.

NH10 and alternate routes

DATA ON NH10 (and the alternate routes from Gangtok and Kalimpong to Siliguri)

Distances - Siliguri to Gangtok
Via NH10 - 114kms out of which approx 90kms is in mountainous terrain. Approx 60kms from Singtam to Sevoke is along the banks of the Teesta river.
a. Alternate route 1 (via Pakyong- Reshi-Algarah-Lava-Sevoke-Siliguri) - 241kms
b. Alternate route 2 (via Rangpo-Chitrey-Kalimpong-Algarah-Lava-Sevoke-Siliguri)  - 205kms

Distances- Kalimpong to Siliguri  
Via NH10 - 67kms
a. Alternate route 1 (via Ghoom -Kurseong) - 99kms
b. Alternate route 2 (via Algarah-Lava- Gorubathan-Sevoke) - 132kms
c. Alternate route 3 (across Relli river- Samthar- Panbu-Kalijhora-Sevoke)

It is estimated that approximately 3000 vehicles use the NH10 daily when permitted.

Images of landslide and traffic snarls in that part of the road

Rockfall at Likhu Bhir after rains on 23Mar2024

Traffic jam at Chitrey (Teesta) due to rock fall at Likhu Bhir, 23Nov2024

Traffic jam at Likhu Bhir on 24Jan2024 at around 6pm

 

As we have reported earlier, Likhu Bhir is an old landslide which was dormant for many years until the GLOF of 04Oct2023 reactivated it.

File photo from July2019

Also as reported, the Teesta river bed has risen by almost 4m all along the valley due to the silt and sand deposits brought down by the GLOF, which makes NH10 much more prone to subsidence/erosion (the TLDP III and IV dam activities and the IRCON tunnelling having contributed their share to making sections of NH10 more prone to subsidence, rockfalls and landslides)

Rainfall (at Kalimpong) from 19Mar to 23Mar2024
107mm.
It was surprising that very moderate rainfall, after almost 4 months of complete drought could trigger so much instability in the Likhu Bhir area.
Recently, I met a geomorphologist who said that the Oct 2023 Teesta Valley GLOF was the biggest such event in the Himalayas in the recent past. I believe him entirely.

My thanks to our WhatsApp group 'HA' members who's photos I have used :)

Praful Rao
Kalimpong district
Darjeeling-Sikkim Himalaya
savethehills@gmail.com
9475033744

Rainfall data of Jun2019 for the Darjeeling-Sikkim Himalaya

 Rainfall data of Gangtok, Damthang and Dentam are from IMD

North Sikkim : The deluge of 17Jun2019

Also read here

ABOUT JUNE 2019 RAINFALL FROM IMD

'June ended with a huge deficit of 33% (for the whole country) but within a span of 10days  from 01Jul to12Jul it came down to 14%'.

- KJ Ramesh,
Director General,
IMD.


Praful Rao
Kalimpong district
Darjeeling -Sikkim Himalaya

Images of the first major landslide in the vicinity of Kalimpong : 05Jul2019/0800hrs

Took place on National Highway 31 between Coronation Bridge and Monpong in W Bengal. Time, approx 0800hrs this morning. I do not have rainfall data of the place but we had 22.6mm of rain between 0500-0630hrs in Kalimpong which 20km away (aerial dist).
No casualties.

Praful Rao,
Kalimpong district
Darjeeling-Sikkim Himalaya

STH activities : Drone over 'ZERO' landslide at Nimbong, Kalimpong (Youtube video)

STH has reported on the landslide at ZERO gaon at Nimbong, Kalimpong here.
On 03Jan2018, STH again went to the area and flew a drone over the landslide from various places around the slide. The 5 min video is below :-



Praful Rao,
Kalimpong district,
Darjeeling Sikkim Himalaya

Preliminary Landslide Report of the ZERO landslide at NIMBONG (Kalimpong) - 30Nov2017

1. Nimbong is a small village located on the eastern fringes of Kalimpong district
(BDO - 1). The gram panchayat has a population of approx 8000 but the town has a population of 2659 (Census 2011). Agriculture is the main source of livelihood here. Being located on the foothills, heavy rainfall associated with thundershowers is a normal phenomenon during the monsoons.
Nimbong is no stranger to landslides with 36 people dying in 1996 and a huge landslide being located at Central Gaon which was reported by SaveTheHills (STH) in July2009 (see STH blog of that month). While the Central Gaon landslide seems to have somewhat stabilized, another landslide seems to be wreaking havoc in Nimbong. This is the landslide at Zero.
2. Zero Landslide
The significance of the Zero landslide is :-

•  It has breached 200m of the vital road connection which links Nimbong, Lava, Samthar, Pabringtarm, Ghanti Dara with Kalimpong and the plains of the Dooars and Siliguri.
• It directly threatens Anuj SUMI school, a branch of SUMI school (Kalimpong) with approx 250 students.
• The landslide crown being barely 200m from Nimbong town also puts the entire town in grave danger in the long term.
  
  This is evident from the Google Image below :-

 

3. Brief History of Zero landslide
As per locals who were interviewed, the landslide started in 2012 as a minor ‘crack’ on the road  below the Anuj (SUMI) school. It slowly became a ‘sinking area’ and this subsidence area on the road became a full blown landslide in 2015. The landslide has been increasing in size since then and in 2016 it totally cut off Kalimpong-Nimbong-Siliguri link. This necessitated an alternate diversionary route across the slide made below the Anuj SUMI School and constructed through MNREGA. This road too was pulled down by the slide in Jun2017.

4. Probable cause

Pending a proper scientific study, inquiries made by STH reveal that:-

• There are numerous natural springs in this area which sprout water and which has been used as a source of drinking water and agriculture by the surrounding villages for decades. These sub-surface water sources as per locals caused sinking zones on the Kalimpong- Nimbong- Siliguri road in this area which eventually caused the landslide.

• Though Nimbong town is in the vicinity, the urban sprawl is still small and may not be contributing significantly to surface run-off and eventual erosion by jhoras which is a major cause of landslides in Kalimpong district.

• A small river or jhora flows at the base of Zero landslide but the impact of erosion caused by this on the landslide also appears negligible.

• There have been no major land use / land cover changes in the recent past which could have contributed to the slide. The Kalimpong-Nimbong-Siliguri road which has been cut off by the landslide was constructed in the 1970s. 

5. Rainfall
Lying in the foothills of North Bengal, this area receives heavy rain during the monsoons in the form of intense thundershowers. This certainly is a major trigger for landslides in this area.
Unfortunately, rainfall data of this region was not available to STH.
6. Location and dimensions of Zero landslide
Coordinates: N 26° 58' 08.4", E 088° 34' 13.8"
Elevation: 1168m/3832´
The landslide today is huge, measured on Google Earth the length from the crown (just a few meters below the school) till the base is approx 700m.
The width at the road is approx 150m.
7. Casualties and losses
Till date the landslide has not resulted in any human casualties, even though locals have reported loss of livestock. As on date five families have been relocated and along with property, livelihoods and farmland has been lost.
But the real danger posed by the slide is in the future, where this slide will:-

•  Destroy Anuj SUMI school, a class 11 standard school with approx 250 students
• Destroy a number of homes which lie on the edge of the landslide zone.
•  Destroy a heritage Church built in 1886.
• Destroy the Nimbong Panchayat office.
• Breach the Kalimpong –Nimbong-Siliguri road which will effectively isolate large areas of eastern Kalimpong district.
• Ultimately destabilize Nimbong town.

8. Suggested remedial measures
What was apparent to STH after spending a day touring the landslidewhat is evident is that time is of essence and in order to mitigate further damage that the landslide may cause, the following remedial measures are suggested :-

• A proper scientific investigation may be done (by the GSI) immediately to find the cause of the landslide and to suggest measures to mitigate further damage.

• Emergency landslide protection measures which include bio-engineering (vetiver, bamboo check dams etc ) as well as other engineering methods maybe commenced so as to stabilize the area before the next monsoons.

• Rainfall data may be obtained and correlated to the activity of the Zero landslide. Manual rainfall gauges may be made available and rainfall data be maintained at Nimbong.

• All inhabitants in the vicinity of the landslide may be made aware of the danger posed by the landslide especially during heavy rain or even minor earthquakes.

• Internet and phone connectivity maybe improved in the area with a view to communicate weather warnings.
  
  

Praful Rao,

Kalimpong district

Darjeeling-Sikkim Himalaya

STHstormwatch : Forecast tracks of storm in the Bay of Bengal (May2017)

Source

Praful Rao,
Kalimpong dist,
Darjeeling-Sikkim Himalaya

STH Activities : With IIIT (Hyderabad) team for landslide familiarization (08/09Oct2016)

One of the central roles of STH has been spreading awareness about landslides - a hazard form whose impact on mountain communities has been neglected and under-estimated to a large degree the world over.
As such we have used every opportunity to engage with visiting teams both from India and abroad in the many landslide familiarization visits we have made over the years - records of all such visits are documented in this blog. In Oct 2016 as a part of this program, we took two visiting delegates of IIIT (Hyderabad) for a tour of landslides in and around Kalimpong on 08/09Oct2016. The institute is working on landslide prediction equipment which they would probably be installing in the Chibo-Pashyor landslide zone.

Praful Rao,
Kalimpong'
Dist Darjeeling