A strange coincidence: Landslide on NH10 at Sethi Jhora on 23Sep2020 and again on 23Sep2023 at exactly the same spot.

On 23Sep2020 a landslide occurred on the National Highway 10 (NH10) at Sethi Jhora, which was covered in the STH blog.

Of the 114km between Siliguri and Gangtok, 90km of the NH10 lies in the mountains and of this approximately 65km is along the banks of the Teesta where a number of dams have been constructed. Now IRCON is also building a tunnel for a railway which when finished approx next year end will link Sevoke with Rangpo in Sikkim.
NH10 is the lifeline for the state of Sikkim and Kalimpong and also a strategically important road and supply route for the Indian Army.

I have reproduced a press clip & photo from the STH blog dated 26Sep2020 below:

Exactly, 3 years later at the same spot (Coordinates 26.93946N 088.44148E, Elvn 233m) and again on 23Sep, an almost identical landslide occurred due to which National Highway10 from Siliguri to Gangtok is closed for traffic since 24Sep2023 (see image below) till date.

Rainfall in Kalimpong on 23Sep2023 was 58.4mm
Annual rainfall in the Teesta Valley is approx 2500-3000mm. The entire region is in Seismic Zone IV.
Why the failure occurred?
I think there are 2 factors at play. First, the Darjiling-Sikkim Himalaya is riddled with out-of-sequence faults that have been active recently. The Seti Jhora practically runs along the reactivated Ramgarh thrust fault core. Such fault cores consist of powdery crushed material that have very little strength.  The roads that run over such zones have much lower strength and load carrying capacity. If you saturate such zones with water chances are that they will liquify and cave in. September end would be a time where the monsoon has been around for a while and has saturated these zones particularly when a reservoir is also underneath it. Such a cave-in also happened in the Birrik fault core last year on the side of the road. No reservoir was involved there. Just the fault core material and rain.

- Prof Malay Mukul, Dept of Earth Sciences, IIT Mumbai

Images of Sethi Jhora (NH10) from STH's archives (2016)

Update on 27Sep2023
I was informed by a Govt Official that NH10 at Sethi Jhora was open for single lane traffic at 11.30am ie after 3 days of closure

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

Once upon a time in 2008 - the story of a ropeway and a dam

Dams often earn the ire of environmentalists and locals alike and with good reason: I am very sure that NH10 (connecting Siliguri and Gangtok) has become more unsafe due to dam operations on the Teesta river. Yet dams also benefit a lot of people.
(see short write up by Dr Vimal Khawas of Sikim University - Vimal is a person who should know since he belongs to Suruk which was a remote inaccessible village before NHPC's Teesta Low Dam Project (TLDPIII) was commissioned in 2013).
I visited TLDP III many times when it was being constructed and have placed below photos of how village people from the Suruk, Samthar and Yangmakum region (of Kalimpong district) used to commute to and from their village to the urban centers across the river Teesta in 2008, when the dam construction was in progress.

Dr Vimal Khawas' take:

Stories and arguments of ecological fallouts and socio-economic fractures abound when we talk about hydro-dams across the Himalayas including in Darjeeling and Sikkim.

However, there are many economic and infrastructural benefits that the villages surrounding these projects have witnessed due to these projects.

The remote villages of Samthar and Yangmakum GP (over ten villages), that were over the years neglected by the government, have directly benefitted from the above projects. One of the major outcomes of these projects, is the two motorable bridges at 27^th mile and Kalijhora areas that connect the remote villages with the mainstream. Villagers used to walk/trek several hrs and take manually operated ropeway to cross river Teesta before TDLP III was constructed. These projects have also facilitated to smoothen the village roads and walking lanes/footpaths. Smaller bridges and culverts have been constructed across villages to ease the difficult lives of the villagers. Besides, NHPC has also aided school children thru scholarships, established primary schools and health centers in selected locations. People in the villages like Suruk, Samthar, Panbu, Yang, Makum etc have been financially empowered after the bridges connected the villages to the market.

This is not to say that there are no negative fallouts of these projects, particularly on the riparian habitations along NH10. The negative impacts have been discussed at length by the researchers and activists elsewhere.

Photo Essay:
Praful Rao
Kalimpong district
Darjeeling-Sikkim Himalaya

Flood scare in Sikkim and Kalimpong district (W.Bengal) - 17Jun2019

The Darjeeling - Sikkim Himalaya has thus far had very deficient in rainfall (see below)

 The SW monsoons finally arrived over the Darjeeling Sikkim Himalayas on 16Jun2019 almost 10 days late and we had relief from the heat here when there was a smattering of rainfall given by clouds shown:

Rainfall figures for 16/17Jun2019 are given (source IMD):

So I was rather surprised when we started getting flood alert messages from Sikkim on 17Jun afternoon on WhatsApp, that due to a 'cloud burst' in North Sikkim, the level of the Teesta river was rising dramatically and parts of Singtam (Adarsh Gaon), a business town one hour short of Gangtok and other low lying areas along NH10 were in danger.

Having kept a close look on the weather and rainfall of the region, which was nowhere near extreme, I personally feel that the dams at Chungthang and Dikchu in Sikkim had released large volumes of water after the rains which resulted in the Teesta river level rising sharply. I am aware that most of these dams are run-of-the-river dams, yet considering the steep descent path of the Teesta river and its turbulence, I do believe the volumes of water released caused the flood-like situation.
In this regard, I refer readers to the Youtube video below:

Updates on the above event:
Rainfall data of 17/18Jun (0830hrs to 0830hrs) available now:
Sankalan: 140mm
Mangan: 70mm
Chungthang: 50mm
(Source IMD)

Praful Rao,
Kalimpong district,
Darjeeling-Sikkim Himalaya