Thursday, February 29, 2024

Chungthang: satellite images of BEFORE and AFTER the Glacial Lake Outburst Flood (GLOF) of 04Oct2023

STH has covered the Glacial Lake Outburst Flood (GLOF) from South Lhonak Glacier extensively in this blog with stories, many images and maps of the devastation which followed all along the Teesta River Valley.
The GLOF hit Chungthang town at around 12.35am on 04Oct2023 causing loss of life and livelihoods and tremendous damage to infrastructure.
Placed above are comparative satellite images of BEFORE the GLOF (Google Earth) and AFTER the floods (NRSC)
The scale of devastation is at once visible - with large swathes of Chungthang town totally covered with debris/sand and the humongous (1200MW) Stage III Sikkim Urja dam destroyed, in the NRSC image of 13Oct2023.

Praful Rao
Kalimpong district
Darjeeling-Sikkim Himalaya

Wednesday, February 21, 2024

Impact of the Teesta Valley Glacial Lake Outburst Flood - Lachen (North Sikkim), the untold story

SaveTheHills (STH) and Junkeri Studio (JS) of Kalimpong have documented the Glacial Lake Outburst Flood (GLOF) disaster of 04Oct2023 extensively in this blog and while doing so we visited numerous places, maybe 20 or so in the Teesta Valley both in W Bengal and Sikkim.
On 17/18Nov2023 we were in Chungthang, North Sikkim where the GLOF destroyed the 1200MW Sikkim Urja dam and saw the humungous devastation there. We interviewed scores of people and photograph them and published the report in our blog – which has been well received all over.
Having gone that far, we were unable to visit Lachen, a small town 39 km north of Chungthang because the roads were totally destroyed by the GLOF. We did make an attempt but the road ceased to exist approximately 5 km north of Chungthang – the road continues to be non-operational even today.

On 17Feb2024 we were fortunate to meet Mr Dathup Lachenpa (DL) a person in the tourism business in Lachen; he had walked across to Chungthang from Lachen because there is still no motorable road.
He was in Kalimpong for brief while and we caught up with him to check how the GLOF impacted town of Lachen. Our interview with Mr Lachenpa:

STH/JS: Welcome, Dathup.
Firstly, can you tell us a bit about Lachen and what is the main source of livelihood there?
DL: The approximate population of Lachen is around 2000, the altitude of the town is approximately 9000’ and main source of livelihood is tourism but there are quite a few government contractors and employees as well.
STH/JS: Lachen was the first 'urban' centre which was hit by the GLOF from South Lhonak Glacier on 03Oct2023.Can you tell us whether you had any early warning regarding the floods since we know there was an Indo-Tibetan Border Police (ITBP) post further north who had issued alerts. Also approximately what time did the GLOF hit Lachen?
DL: I am not sure of the exact time when the GLOF hit us but it must have been around midnight – we were sleeping and heard this sound like a huge wind which woke us up. My home is a little above the town and when I went outside, there was no storm – the weather was quite clear and I could see stars in the sky. Since there was no storm but the loud noise persisted, I suspected something must be happening in the river and then I saw a lot of smoke rising there, that’s when I realized it maybe the river was overflowing or it was a landslide. I never expected the GLOF (from South Lhonak Lake) to be hitting us. I only realized in the morning that this was a major disaster when we went out towards the river and saw how much devastation was caused by the force of the river. At around 12.30am on 04Oct2023, the electricity and cell phone system went off. I expected a lot of damage by the impact but never on this scale of devastation.
STH/JS: How close is Lachen to the Teesta or more correctly Lachen Chu river? Is the town of Lachen on the banks of the river?
DL: Lachen town is located on higher ground, a little above the river.

Lachen town

STH/JS: Was there any destruction or damage to property or were there any fatalities in Lachen due to the GLOF?
DL: Yes, we ourselves lost a new home which we were constructing and I believe two labourers from Border Roads Organization (BRO)were swept away from the banks of the river at Zema.Zema is slightly north of Lachen towards the glacier.
STH/JS: And in all this you did not get any early warning whatsoever?
DL:As far as I know, we did not get any early warning.
STH/JS: Do you know if the government authorities or Phipon (Headman) received any early warning? - the ITBP post near the glacier sent some warnings, were they received at Lachen?
DL: The ITBP camp is located up there at Zanak 2, maybe they informed their people downstream but nobody informed us.
STH/JS: So what you are saying is that the casualties were limited and damage was less only because Lachen town is located at higher ground and the Lachen Chu or the Teesta river flows in a valley below.
DL: Yes
STH/JS: What is the damage to infrastructure and bridges around Lachen?
DL: There was a lot of damage. In Lachen, 4 bridges were washed away. 3 bridges connected Lachen to Chungthang and one connected us to Thangu.
STH/JS: Have these communication lines (bridges) been restored?
DL: Communication towards Thangu has been restored, with an army bailey bridge being constructed, so light vehicular traffic is now possible. This bridge is on the river bed and may not survive the monsoons so they are re-building the other one.
Three bridges towards Chungthang were washed away, so the route has been diverted and now there is only one bridge which has to be crossed at a place called Boonsoi, 10km south of Lachen. This RCC bridge at Boonsoi survived the flood.
STH/DL: We know that the BRO is working on the road from Chungthang northwards to Lachen. I believe the progress of this work is very slow and I also know people from Lachen are working on the road towards Chungthang.
DL: Yes, we (Lachen public) have succesfully completed one portion from Lachen towards Chunthang which was very difficult at a place called Taru. We encountered only solid rock there. The BRO helped us and we have managed to clear that section for vehicular traffic so the road upto Menchithang, a distance of approx 20km from Lachen is motorable. So now we have to walk 7-8kms after which we reach another motorable section towards Chungthang.
In this regard, the Lachenpas made three wooden bridges.

Local people together with BRO personnel carving out a new road from Lachen to Chunthang

The Lachenpa community constructing a wooden bridge across the Teesta river (also called Lachen Chu) at Zema to connect Lachen with Thangu. Notice the large landslide in the background

STH/JS: We know that Lachen was marooned for some time after the GLOF, can you tell us how many days you were totally cut off and how did people in Lachen survive?
DL: At that time almost 70% of the people were in Thangu, harvesting potatoes and radish and the rest were in Lachen. We habitually stock rations and that's how we survived - on stored rations.
STH/JS: Did the army or air force also help in ration supply?
DL: No, but they certainly helped with the evacuation - the relief material came from local people of Sikkim.
STH/JS: Were there any tourists in Lachen at that time and how were they evacuated?
DL: Yes we had around 500 tourists who were stranded in Lachen at that time; they were evacuated by AF choppers from Chatten (army base near Lachen).
STH/JS: What was the impact of the disaster on livelihoods of people?
DL: The impact is huge because we lost a lot of revenue in tourism – Oct to Dec is a big tourist season for us and we have lost these 3 months and we are not certain in 2024 as well, because road access to our area is still not possible.
STH/JS: Fortunately, it did not snow heavily in North Sikkim during this winter and as such you did not have much problems with ice-bound roads etc. How concerned are you about the forthcoming monsoons with the road condition being what it is? How will you manage your supplies?
DL: Getting supplies through thru Dongkha La pass (which is at 18,000’) would be impossible but what people do is that during the annual puja time in winters they buy a lot of rations from monks and stock up – also people in Lachen were stocking up dry rations like oil and rice from Menchithang etc thru porters who would carry the stuff. However, we would have a problem with LPG cylinders (even though we have fire wood) because people largely use gas for cooking these days.
STH/JS: What about health care issues in Lachen after the GLOF?
DL: Yes, this is a major concern. Recently a 27yr old man from Lachen died in a hospital in Siliguri because he had to be evacuated through Dongkha La pass (18,000’) when he was ill; this is a huge challenge for a sick person. So right now, we are most scared of falling sick in Lachen and hope that no one becomes unwell because we only have a primary health centre which does not have many facilities and presently, I don’t think we have a doctor there.
STH/JS: So what happens to the sick and elderly people at Lachen?
DL: (Chuckles) – We just pray that no one falls ill.
STH/JS: What about children’s education?
DL: They were at home during the winter holidays and have now returned to school – some of them went by car through Dongkha La pass others walked back to Chungthang etc – most of them, walked back I think, because they were scared of heights at Dongkha La.
STH/JS: The hikers trail for walking back (between Lachen and Chungthang) seems very precarious
DL: Yes, the footpath for walking is quite dangerous, if one slips there is no chance of survival – at many places the path is not more than a foot wide.
Makeshift wooden ladder which is used while walking from Lachen to Chungthang

Narrow and dangerous footpath which is being used by people who walk from / to Lachen today.

STH/JS: So how long do you from a layman’s perspective, expect the Chungthang – Lachen road to be restored?
DL: Our Chief Minister had promised that after rebuilding the bridge in Chungthang town, all the resources (machinery and manpower) would be diverted to the Lachen road. That has not happened. Yes, machines are there but not the type which is required to cut rock and so on. We were hoping that road communication would be restored within 2-3months but it has been 4 months and progress is very slow. With no heavy earth moving machinery at site, people are saying it may even take a year for the road to be restored.
STH/JS: Immediately after the disaster, were there any homeless people or was there any requirement for relief and shelter?
DL: Some areas and parts of roads especially in the bazar (town) were cracked and people were reluctant to live there, because of rumors and continuous landslides. So people shifted to relative's home at higher grounds near the monastery. However, there were no homes which were destroyed in Lachen.
Relief supplies as far as I can remember, came in after a week or so. I think this was contributions from locals in and around Sikkim and it was flown in by choppers.
STH/JS: Can you tell us more about the Chungthang-Lachen road status again?
DL: Before the GLOF, the Chungthang-Lachen trip used to take 1 hour by vehicle. Now we can travel by vehicle from both Lachen and Chungthang but the midsection is still not motorable and we have to walk that stretch and it takes us around 2hrs. The vehicles used are all SUVs with 4 wheel drive.
Impact on road communications by the GLOF: Lachen-Chungthang road at Menchithang
                                       Landslides along the Lachen Chu (river) valley

STH/JS: You mentioned visiting the Lachen Chu river a number of times after 04Oct2023 – can you describe the scene? Were there any landslides? And how did people from Lachen spend the next few days after the GLOF?
DL: The power supply and mobile networks went dead from 04Oct2023 – people were scared and moved here and there, trying to find out what was happening. We noticed the river was still swelling up and there were lots of landslides taking place in and around. When we went to Zema where there was a bridge which connected Lachen to Thangu, we found that the landscape had changed totally, we could not recognize where the bridge was. The whole day the river was flowing at the same high level.
Two days or so later when we went towards Zema again , we found a huge increase in landslide activity all along the road.
STH/JS: We are aware that a Swiss and Govt of India team had gone upto South Lhonak Glacier (in 2023) – did they go through Lachen?
DL: We heard about that too but I do not know the details. People were in fact blaming them for what happened – and believe that they may have done something. We believe our lakes are sacred and do pujas and visit monasteries while visiting these (holy) places.
STH/JS: Which is the nearest lake from Lachen?
DL: By road, it is Gurudongma lake
STH/JS: How much time would it take to reach South Lhonak lake from Lachen?
DL: Now there is a motorable road to Zanak 2 where they have the last ITBP camp and that takes around 6hrs from Lachen. Beyond that I have no idea.
STH/JS: Do you know whether (the ITBP camp at) Zanak 2 was affected by the GLOF?
DL: I think so, I think I saw some photographs.
STH/JS: Have people returned to Lachen from Thangu?
DL: Yes, its wintertime and its not possible to stay in Thangu. Everyone has returned but some are in Gangtok and others in Siliguri etc and children have returned to school.
STH/JS: What is the approximate economic loss which took place due to the GLOF say in terms of loss of farmland,destruction of orchards etc
DL: I can say we have lost a lot of land – pasture land for example. Our dairy animals go to lower altitudes during winters, to places like Denga which was a little above Chungthang. These areas have been washed away by the GLOF. People are now living on the roadside at Rabong and so on. Further, I think in terms of loss, all of Sikkim has been impacted - shops, hotels and so on . I am sure the loss is huge and in many crores.

                              Destruction of farm and grazing land at Menchithang.
                                               Landslides along the valley at Zema

STH/JS: Do you know of any loss to Govt departments including the army?
DL: Fisheries department have lost some trout farms, animal husbandry department have lost their angora farm, Tibetan sheep have lost their grazing land and so on.

                                    Destruction at army camp at Menchithang

STH/JS: What sort of help have you received from the administration?
DL: It has been four months since the GLOF and we still have not seen the District Magistrate (DM) on site or anywhere. We met the ADC (Additional District Collector) who came to Lachen after 7-8 days, maybe he was representing the DM – we don’t know.
With the help of the Government, the electricity was restored after 8-9days, most probably because we have a new power station in Lachen, which was not affected by the disaster. Our cell phones (only BSNL network) started working after a month or so but the performance was poor, with a lot of disturbances
STH/JS: You mean you had no communication for a month?
DL: No, I think the ADC had come with a satellite phone but I am not sure how many could make calls. We also could use the army lines but that too was difficult because of the long queues of people waiting.
STH/JS: How do you see the next few months with the monsoons coming up?
DL: We are really scared of the monsoons and the heavy rain it will bring. It will affect us a lot and people are thinking of stocking supplies before the rains and we will avoid traveling during that time because of the road conditions.
STH/JS: Can you tell us the cost of travel from Lachen to Chungthang via the Dongkha La pass?
DL: I heard the freight charges of utility (short body) truck bringing supplies from Mangan to Lachen via Dongkha La is Rs 25,000/-
STH/JS: Thank you so much for your time, Mr Dathup Lachenpa and for sharing this information about what happened in Lachen. It will certainly be most useful for people studying the October 2023 GLOF disaster in the Teesta Valley.

Photo credits: Dathup Lachenpa

Praful Rao
Kalimpong district
Darjeeling - Sikkim Himalaya
Praveen Chhetri
Junkeri Studios

Wednesday, February 14, 2024

Impact of the Teesta Valley Glacial Lake Outburst Flood (GLOF) - updates from North Sikkim (Feb2024)

As has been reported by us in this blog, the GLOF disaster of Oct2023 devastated large parts of the Teesta valley both in Sikkim and W Bengal. Placed below are some recent updates from North Sikkim:
Naga area of Mangan district
The devastation in Naga and Toong area of Mangan district has been covered here.
Recent (09Feb2024) closeup photos of landslide affected areas of Naga are shown below:

A telephoto image of the same area which I took from the opposite hill on 18Nov2023 (below) reveals hardly any change in the intervening 3 months.

As per my source in Chungthang, people from these homes have evacuated and are living with relatives or at rented places.
Toong bridge and road status
The GLOF of 04Oct2023 destroyed the bridge over the Teesta river at Toong (see photo of 18Nov2023 below). This bridge connected Mangan (dist HQ of North Sikkim) with Chungthang

A 'log' bridge (below) built in this area has temporarily restored this communication route.
However, for the time being the bridge is closed between 10.00am to 4pm to allow road repairs as such commercial vehicles and others still have to route via a long route via Saffo- Shipgyer - this route not only takes double the time but is narrow and dangerous at places.
As per information received, the progress of repair of Chungthang - Mangan road and also the Chungthang - Lachen road is slow and this is worrisome since the pre-monsoon season accompanied by intense thundershowers are due to start in March 2024.
Here are some rough stats:
a. The freight charges for a truck with 10 tonnes of load from Siliguri to Chungthang was approximately Rs22,000/- (incl of taxes), when the main roads were available.
b. Now, since the main roads are not available, the detours have pushed up the freight charges to Rs 31,000/- and also the trucks can only carry 8-9 tonnes of material on the alternate route.
c. So because the freight charges have increased while the load which is being carried has decreased - a single brick in Chungthang now costs Rs18.
Chungthang town
Among all the urban centers impacted, the GLOF dealt it's severest blow to Chungthang town at around 12.35am on 04Oct2023. We have covered it in detail here
Even when we visited the town on 18Nov2023, more than a month after the devastation, the whole place still looked like a war zone but I am glad to know that the people of Chungthang are slowly getting back on their feet again. Placed below are recent images of Chungthang town where the almost 10 feet of sludge mud and sand which buried the streets, homes and buildings have been cleared off and shops are open and life is slowly getting back to normal.

Praful Rao
Kalimpong district
Darjeeling- Sikkim Himalaya

Wednesday, February 7, 2024

The Firefighting of Darjeeling’s waste problem

Toxic fumes and smoke billows from tons of garbage and waste which are on fire at Darjeeling town's solid waste dumping ground or 'chute' in Feb2024. Like most Himalayan towns, Darjeeling simply believes in removing the waste from the town and offloading the untreated waste in a remote area (Photo Credit: Zero Waste Himalaya)

On the night of January 28, 2024, the waste dump of Darjeeling caught fire once again. Yet again, the Darjeeling night skies glowed orange, spreading panic among residents close by. It was not even a year back on June 14 2023, when a similar fire had simmered over 4 months and it had taken the Darjeeling Municipality over 60000 litres of water transported through tankers to douse the fire. The alarming situation created a buzz in the media, provided a bit of opportunity for mud slinging and blame games, but as the fire went out, all conversation around it also died down.
What must have been a remote location during the the days of the British Raj is now Amar Jyoti Gram, Municipal Ward No 17 of Darjeeling town and this is where the town's solid waste continues to be dumped. We visited the site on 01Feb2024 - the fire was still burning, despite being doused with huge quantities of water. (Photo credit - STH)

The dumping site going ablaze undoubtedly draws much needed public attention to the problem but fails to shake the town into solving it. Let's not forget that the smoke from the smouldering dump has been contributing to Darjeeling’s polluted winter air for over a decade now (Darjeeling Burning!). All of the unsegregated waste dumped in the chute has been burning relentlessly, with the fumes enveloping the town in its toxic shroud. Living in such toxic and hazardous situations has somewhat become the norm for Darjeeling every winter, and this is highly concerning.
The chute on fire on 01Feb2024. The decaying organic matter produces flammable gases (mainly methane) which after catching fire continues to burn despite best efforts to extinguish the fire. (Photo credit - STH)

In response, Darjeeling, like so many other places, has quite literally been firefighting to keep the problem at bay. What is needed are longer term vision and strategies grounded on community ownership and individual actions. While waste profiles and demographics have undergone massive shifts over the years, our management systems are struggling to catch up with the changes. With mindless consumerism fueled by social media and the frenzy of online shopping, we are buying unnecessarily, and our waste piles are increasing by the day. Single use products that are non recyclable make up a bulk of the trash from our households that ultimately end up in the dump site mixed with biodegradable waste. (What Lies Beneath! The Truth about Darjeeling’s Waste)
The waste dump lies directly below Darjeeling town and the wind takes the toxic fumes, miasma and smoke directly into the town. Seen here in the foreground are built up areas in the dump site and new houses being built there; in the distance are Singmari and the Himalayan Mountaineering Institute complexes. (Photo Credit - STH)

Individually and as bulk generators, our waste footprint has increased dramatically, but our responsibility towards managing our own waste has remained pitifully low. It is a struggle for local bodies to collect the monthly garbage fee to manage the waste we generate. Our houses may be tiled to the ceiling, but the simple practice of waste segregation is still an unthinkable chore for most of us. Segregation at source is the fundamental step to a sustainable waste management system. Without community support and ownership, long term strategic solutions will always remain elusive.
The urban setting around the 'chute' today. (Photo credit - STH)

It is time for all of us to take cognizance of the hazardous conditions we are creating and take concrete steps to resolve it. Zero Waste Himalaya, has developed the 8 steps strategy to move towards sustainable waste management which requires ownership and participation from the community as well as strong commitment and vision from elected bodies. -

1. Build citizen action and stewardship - Waste is everyone's business as all of us are
producers and managers of waste. To have a successful waste management system,
it needs community ownership and stewardship. This can be brought about by
participatory planning processes, ownership of action and continual community
engagement and knowledge building.

2. Adopt decentralised waste management at ward level or ward clusters- Decentralised waste management reduces the volume of waste to be managed, and makes the task of monitoring easier. Material recovery facilities can be developed for waste sorting and storage, with linkage to recyclers. With the goal of reducing landfill load, only ultimate discards should be sent to the landfill.

3.Implement segregation of waste at source - This is already mandated by the Solid Waste Management Rules of 2016 that stipulates segregating into biodegradable, non-biodegradable and hazardous.

4. No biodegradables to landfill - If segregation is practised, then the biodegradable waste can be managed separately. There are options for home composting, community composting or bulk composting.

5.Target bulk generators - Bulk generators such as hotels, restaurants, hostels, offices, markets generate waste in large volumes. They have to be targeted and their waste managed separately. SWM Rules mandates bulk generators to manage their biodegradable waste and not send it to the landfill. Food, vegetable and meat waste can be managed as animal feed, compost or through biomethanation. 

6. Strengthen and expand single use plastics ban - Increasing plastic production and consumption is the root of the Himalayan waste crisis and reduction of this waste is the real solution. This reduction of plastic can be achieved with the implementation of single use plastic ban that India has enacted since 1 July 2022 but a number of these banned SUP are still used in Darjeeling. For the Himalayan region, there is a need to expand this ban to other single use plastics like bottled water (especially the tiny one) that will enable the reduction of plastic waste to the landfill.

7. Invest in pilots (wards / institutions) - Pilots are a good way to showcase the immense possibilities as well as learn while doing. This can be a tool for others to learn and scale up from.

8. Invest in capacity building of all stakeholders (elected representatives / CBOs / Officials) The changing profile of waste has meant that traditional waste management systems of rolling down the hill and burning proves toxic and there is a need to shift the narrative in policy and practice. Leading by example is one of the most powerful actions thus elected representatives and community gatekeepers can be powerful agents of positive community change. A Zero Waste Learning Center can also be planned in a convenient location which can act as a constant source of learning on waste management for all stakeholders. 


Beyond all this, companies that are sparing no cost to send their plastics up the mountains need to be held accountable for managing it or taking it back. There is a need to close the plastic tap, especially those that are unnecessary, single-use and having no solutions. This is already enshrined in the Extended Producer Responsibility Rules 2022 under the Plastic Waste Management Rules, 2016 and this needs to be implemented in the mountain states. (Plastic crisis in the mountains: Will extended producer responsibility bring in change).

Zero Waste Himalaya is a platform of organizations, institutions and individuals working on issues of sustainable waste management and advocating for effective producer responsibility in the mountains. 

Write to us at

Follows us on FB / Instagram: @zerowastehimalaya

Priya Shrestha
Roshan Rai


Wednesday, January 24, 2024

AFTER THE FLOOD - By Pemzang Tenzin (Mangan, North Sikkim)


Zanak, at the base of the aptly named Sentinel Peak, is the last outpost on the lesser used but religiously and historically important Chorten Nyima La route to Tibet.  The ITBP personnel stationed there first raised the alarm on the South Lhonak Glacial Lake Outburst Flood (GLOF) and possibly saved the lives of many people in the path of the ravaging flood.

 South Lhonak Lake, like many other glacial lakes, is meltwater stored behind a fragile dam created by debris and ice left behind by the snout of the retreating glacier.   The 1950 Swiss Foundation map of Sikkim, based on earlier Government of India surveys and still used today by trekkers and mountaineers, does not show a lake at this location.  The lake has grown from nothing to its present dimensions of more than 200 standard football pitches within a span of less than a hundred years.  The glacier is expected to recede further and the size of the lake will increase in the very near future. The volume of water stored is thirteen times the storage of the erstwhile Teesta Urja reservoir.  It is estimated that half this volume spilled out during the October GLOF event.

This is a story repeated again and again in others parts of the high mountains as the ice cap starts melting at an accelerating rate due to the effects of climate warming.  The Eastern Nepal, Sikkim and Bhutan regions are considered a hotspot for GLOF activities.  In Sikkim, the total area covered by ice caps is larger than the size of some of the districts.  The Swiss Consortium, in partnership with National Disaster Management Authority (NDMA) is studying some of these lakes.  They have compiled a list of twenty five lakes in Sikkim that have been red-flagged by different agencies as being potentially dangerous.  Twenty four of these are located in North Sikkim, almost equally distributed along the Lachen and Lachung axes and one in West Sikkim.  With increased melting and the recession of glaciers, more lakes are expected to form or increase in size, making new areas in other areas of Sikkim vulnerable to GLOF.

Sikkim’s limited experience with mitigation measures for dangerous lakes, like siphoning of the same South Lhonak in 2016 and controlled breaching of Mantam in 2017, has met with at best limited success. The NDMA-Swiss Consortium project involves studying the South Lhonak Lake and the Shako Cho as exemplars to suggest mitigation measures or to design an Early Warning System.  Without ground access, the Swiss experts had already completed the desktop studies based on satellite imagery.  Due to security reasons, the team could only make its first field visit in September of 2023 but before the team could even take stock of their visit, South Lhonak Lake surprisingly burst on October 3rd.

 It is difficult to create an accurate time line for the GLOF event and the arrival/peak flows at different towns as both public and official reports vary considerably.  This is due to the fact that the flood happened in the middle of the night and it builds up gradually from first arrival to peak flood levels over  a matter of hours.  The ITBP camp noticed the level rise in the Goma Chu, the effluent stream from South Lhonak at about 10.30 at night (the Print), though the triggering landslides and the breaching of the lake must have happened at least hours earlier.  In India, Central Water Commission (CWC) monitors flows, including GLOF, in all the significant rivers through a network of instrumentation.  Hydrologist/activist Himanshu Thakkar writes in his blog that the automatic stations upstream of Dikchu, including Lachen stopped reporting sometime before 10.30 pm on October 3rd and, in his opinion, these stations were probably non functional.  Downstream of Dikchu, instrumentation show the river rose by about the height of a three storey building at Khanitar (near Manipal) and by about a five storey building at Melli where the CWC stations are located.  At these locations, the floods first arrived at around midnight but took a couple of hours to build up to maximum flows. 

 The actual levels recorded at Khanitar were more than twice as high as predicted in  the CWC simulation for South Lhonak GLOF published in their advisory in 2016.  Gazoldoba near Siliguri, located a couple of hundred kilometres downstream of the GLOF source, recorded high flows (more than 7000 cumecs above pre flood flow) despite the flood flowing through a number of manmade and natural impedances on its long journey downstream.  The flood marks recorded at RangRang also augments this observation that the flows on October 3rd/4th were much higher than those simulated both by CWC and the Swiss consortium.  The flood marks upstream and downstream of Chungthang could also provide an estimate of the effect of the collapse of the dam on flood flows.

 The dam failure at Chungthang has highlighted the vulnerability of power projects and the inadequacy of the existing safety protocols in the face of abnormally high flood flows associated with GLOFs.  The dams are not designed for overtopping and the amount of water it can manage are conventionally calculated from hypothetical rainfalls in the catchment area.  While repairing and rebuilding the damaged or collapsed dams, GLOF has to be factored in.   There is a need to have a relook at the hydrological design and flood response protocols of all existing dams in Sikkim and elsewhere in the Himalayas.  It is reasonable to question whether the reservoirs were operating at minimum levels in October (monsoon period) as required by safety protocols and whether the gates were working properly.  There is a need for more oversight from dam safety committees in the state (if it exists) and the centre at both the design stage and during operations.

 Chungthang is built on a triangular river terrace at the confluence of the Lachen and Lachung rivers.  River terraces are ephemeral geographical features which seem doubly vulnerable to both GLOF and the shaking of earthquakes.  The October 3rd/4th GLOF seems to have severely damaged or wiped out most of the river terraces upstream of Dikchu along with infrastructure and property built on them.  Parts of Toong and Rel villages built on Talus slopes on the Teesta a few kilometres downstream of Chungthang are collapsing due to undercutting by the flood.  Here, the houses on and below the highway have toppled while those above the highway have also developed cracks and may not survive the next monsoon.  Reports of cracks in structures in other areas situated on hill slopes above the banks of the marauding flood also needs to be investigated empathically.

 Whether it is landslides, GLOF or any other natural disaster, the best mitigation measure is avoidance of the vulnerable area.  Past experience shows that once the disaster is temporarily abated, people double down and start rebuilding in the vulnerable areas.  Due to ad hoc decision making and paucity of funds, Government departments usually put promises of resettlement in the back burner with the passage of time and slowly forget about it.  With our increasing populations and increased exposure to multiple hazards, there is a need to legally prevent development and houses in the designated disaster prone zones and to formulate comprehensive and humane disaster rehabilitation policies. 

 Beyond activism and partisan politics, we need to rationally study and understand these constantly evolving and growing natural threats to our society and learn to cope with them.

Pemzang Tenzing

Wednesday, December 13, 2023

BBC covers what the Indian National Media missed: The 04Oct2023 GLOF disaster in the Teesta valley

The BBC has today covered the 04Oct2023 GLOF disaster in the Teesta valley here and although the report by Cherylann Mollan, Mumbai has many glitches and errors, I welcome BBC's coverage merely because the National Media has covered it too sketchily or missed it out altogether and the Central and State Governments of Sikkim and W Bengal seem to think the GLOF incident was too insignificant, affecting too few to be bothered about.
Of the many errors in the report, I can point out a few glaring ones:

  • The 04Oct2023 disaster has somehow been named the 'Sikkim flood disaster' which precludes large downstream areas in Kalimpong district (W Bengal) which were also badly affected by the GLOF. This has been made worse by W Bengal government not even considering the event, a disaster.
  • In all probability, what triggered the GLOF was a large landslide or an avalanche and NOT a cloud burst as mentioned by the BBC. Read here
  • The GLOF which started from South Lhonak Lake (elevation approx 17,300') late in the night of 03Oct2023, wrecked many areas around Lachen but the first major town (not nearby village) it devastated was Chungthang (elevation 5,500') approximately 62km downstream and where the Sikkim Urja Stage III 1200MW dam was located. The dam was destroyed by the GLOF which hit Chungthang at 12.35am on 04Oct2023.
    What remains of the 1200MW SIkkim Urja StageIII dam at Chungthang (Photo date: 18Nov2023)

We were in North Sikkim between 17-19Nov2023 and our reports on the devastation in Chungthang town and its vicinity may be read here
Drone photo of devastation in Chungthang town (Photo date:18Nov2023)

I totally agree with Mathew Payne's (the School of Geography, Geology and the Environment at the University of Leicester) statement in the BBC article:

"This catastrophe is a stark reminder of the escalating challenges faced by the verdant Himalayan regions and the increasing magnitude of flooding events necessitates resilient infrastructure capable of tolerating climate-induced excessive rainfall"

which is why we emailed our report and recommendations on the 'Teesta valley GLOF disaster'  to the NDMA and SDMA's of Sikkim and W Bengal on 10Nov2023. The recommendations are essentially short term, aimed at tackling the Monsoons of 2024 which are just 3 months away.

We are yet to receive any reply to our report.

My thanks to BBC for this report on the 04Oct2023 Teesta Valley GLOF disaster.

Praful Rao
Kalimpong district
Darjeeling-Sikkim Himalaya

Thursday, December 7, 2023

Side effects of the GLOF disaster - a trucker's strike in Kalimpong (04Dev2023)

One of the major impacts of the GLOF of 04Oct2023 was its effect on road communications in the lower parts of the Teesta valley that is, on NH10 which connects Gangtok to Siliguri.

About NH10

NH10 is an arterial road, vital for the nation’s security; it is the lifeline for the border state of Sikkim and for Kalimpong district in W Bengal.

Of the 114km distance between Siliguri and Gangtok approximately 92 kms of NH10 lies in mountainous terrain and for much of this distance, the highway winds itself along the banks of the Teesta river. Several large dams have now been built on the Teesta between Chungthang (Sikkim) and Coronation bridge (W Bengal) and many more are planned. The proximity of the river to the highway and the dam activity in this area has undoubtedly contributed to the instability on NH10. The 44.9km IRCON/NFR single lane railway project between Sevoke and Rangpo which has 85% of the distance in tunnels also runs close to NH10 along the valley. This is also creating problems with the excavations from the tunnels and sludge affecting traffic.

This area receives approx 2500-3000mm of rainfall annually and has a lot of landslide activity as such there are many 'hotspots' or large and troublesome landslide areas which routinely disrupt traffic during the monsoons both in the 38km Sikkim section (from Rangpo to Gangtok) and the much longer (62km) W Bengal section (Rangpo to Coronation bridge). The entire region is in earthquake zone IV.
Normally, approx 3500-4000 vehicles ply on NH10 each day from Sikkim, Kalimpong to Siliguri.

The W Bengal section of NH10 is being maintained by the PWD (W Bengal) except for a small portion between Teesta Bazar and Geil Khola which is with NHIDCL. Maintenance of the 28km part in Sikkim from Rangpo to Ranipul is again with NHIDCL

Source: NHIDCL
Current problems   
The GLOF of 04Oct2023 shredded many parts of NH10 and for some time the Kalimpong - Melli section of the highway and the Kalimpong to 27th mile sections were closed due to damage.

Drone photo of NH10 opposite Melli bazar, on 10Oct2023 which had been eroded away by the GLOF
Part of NH10 towards Sikkim from Teesta bazar after the GLOF on 10Oct2023
Part of particularly troublesome part (between Teesta bazar and Geil khola) of NH10 on 18Oct2023. 'A' is Geil Khola which was severely impacted by the GLOF and 'B' is Likhu Bhir landslide area which has been reactivated by the GLOF.

Vehicular traffic quickly resumed on the Teesta - Gangtok section of NH10 and we could report on the impact of the GLOF at Melli and Bhalukhola on 10Oct2023. The Teesta to Coronation bridge section required more time and was only opened for light vehicles (4 wheelers) and between 6am-6pm on 21Oct2023.

On 04Dec2023 truckers from Kalimpong supported by truck unions from Sikkim and also minibus operators called an indefinite strike alleging long delays in repairing the Teesta - Coronation bridge section of the highway. See map below:

* ABCF is the normal NH10 route (in the mountains) for all vehicles . Now this route is only OPEN for light vehicles. On this road, the Siliguri - Gangtok distance is 114km and takes approx 4hrs.
* Section CF is closed for 6 wheeler trucks and buses and other heavy vehicles.
* Because of the CF closure, heavy vehicles from Gangtok and Kalimpong have to detour thru ABCDEF route ie drive thru Kalimpong town, to Lava & Gorubathan which is 228km and takes approx 7 hrs
* Otherwise heavy vehicles have to follow the route shown in blue (241km) ie ABDEF route which again takes 7 hours plus.
Heavy vehicular movements disrupt traffic as such they are only permitted to ply at night thru urban areas, so I met a truck driver from Sikkim enroute to Siliguri, taking a nap at 10.00am on the roadside, because he had a 7hr drive ahead in the night.
NH717A is under construction and is not available to traffic.
A smaller alternate route from Kalimpong across Relli river then thru Samthar and Panbu and Kalijhora is available for light vehicles. However, this route is not suitable for heavy traffic and is at places desolate.
Lastly, a major problem with the alternate routing thru NH717A and the current Lava - Gorubathan routing is that this area receives almost 4000mm rainfall annually, has severe thundershowers during the monsoons and has a number of large landslide zones such as that in Nimbong.
Video of heavy night time traffic thru Pedong bazar courtesy Amod Pradhan
Damaged culvert at 11th mile Kalimpong due to movement of heavy trucks from Sikkim and Kalimpong to Siliguri.

Luckily, the strike was quickly called off with the District Administration assuring the striking transporters that the Teesta - Coronation section would be opened to heavy vehicles and buses from 10Dec2023.

In all this, the plight of truckers and bus operators who have to do a grueling 7-9hr drive from Gangtok to Siliguri is understandable - it is a tough and tiring drive, mostly along mountain roads.

Freight charges of a truck from Siliguri to Kalimpong have gone up from Rs 8,000/- to roughly double that ie Rs 15,000/- and the drivers take two days to complete a round trip.

On the other hand, the caution on the part of the district administration is also very understandable. The Teesta bazar to Sevoke section of NH10 has always been a particularly vulnerable area with numerous 'hotspots' and the GLOF has only made these places weaker. Opening NH10 to full traffic in haste and without any restrictions may expose travelers along the highway to dangerous and weak areas and we have already witnessed a number of accidents along NH10 recently and even some fatalities.

Praful Rao
Kalimpong district
Darjeeling-Sikkim Himalaya