Extreme rainfall event in the Eastern Himalayas: 04/05Oct20205 (Part II - 'The damage and fatalities in Nepal and Bhutan')

The October 2025 rains (see previous blog) were among the most intense to strike Eastern Nepal, the Darjeeling Himalayas, and Bhutan in recent years. The storm system, which crept in from northern Uttar Pradesh and Bihar, tracked east-northeast, impacting Eastern Nepal — including Kathmandu — first. The devastation it caused has been extensively covered by the media. Below, we’ve compiled a selection of key excerpts:

Nepal

Rainfall data (mm): Kathmandu 145, Rautahat 330, Ilam 330mm (reported 37 fatalities)

Fatalities, damage and cost:
a. 66 fatalities have been reported, 69 people are missing. 37 people died in Ilam district.
b. Huge damage on development infrastructure like roads, bridges and drinking water projects across Koshi province amounting to Nepalese Rs2.06 billion. Road projects worth about Rs190 million have been lost in Ilam alone.Bridges worth an additional Rs385 million have been destroyed. 226 homes were reported submerged in Kathmandu and a total of 4,059 households affected (ReliefWeb / GDACS summary of national reports).
c. Across Panchthar, Taplejung, Sankhuwasabha, Solukhumbu and Okhaldhunga, dozens of rural roads have been blocked or buried under landslides. Of the 73 roads, 44 still remain completely obstructed, while 12 of 23 motorable bridges have been totally destroyed. A total of 20 suspension bridges remain impassable due to flood damage.

Bhutan

Bhutan lies directly to the east of Kalimpong district (West Bengal) and Sikkim. As the powerful October 2025 storm swept across the Darjeeling–Sikkim Himalayas, it reached Bhutan on 5 October, bringing with it widespread devastation. The rainfall recorded during the event is shown in the map above.
Like Nepal, Bhutan is crisscrossed by several major rivers — Jaldhaka, Diana, Torsa, Sunkosh, Raidak, Jayanti, and Kaljani — which flow from its mountains into the fertile plains of North Bengal and Assam. These rivers are lifelines for irrigation and agriculture in the region. However, intense rainfall in Bhutan’s highlands often translates into dangerous flooding in the plains downstream.

Fatalities and damage reported

As per The Bhutanese, '3 people are likely dead as two persons are reported missing in Haa Dzongkhag due to flash floods in Sertena, Gakiling Gewog and one was washed away in Kazhi in Wangduephodrang. 1 body from Haa was recovered on 6 October 2025 from Cooch Bihar'.
Further '17 bailey bridges, six suspension bridges, three culvert bridges, three wooden bridges and three private bailey bridges were washed away'. Details of the damage are available here.
According to Kuensel, Bhutan’s national newspaper, “across Bhutan, numerous roadblocks, landslides, and washed-out bridges have cut off several communities. The southern and western highways have reported significant disruptions, and several homes have been damaged or flooded.”

One of the most critical impacts was on the country’s extensive hydropower infrastructure. Authorities in North Bengal were placed on high alert after a technical failure at the Tala Hydropower Dam caused it to overflow, sparking fears of downstream flooding in the Dooars region.
In response to the severe weather, five major hydel projects — Tala, Suchhu, Dagachhu, Punatsangchhu, and Chhuka — were temporarily shut down. This unprecedented situation not only disrupted power generation but also highlighted the growing vulnerability of Himalayan infrastructure to extreme weather events.

Further details on the damage to Bhutan’s dams can be found here.

Praful Rao,
SaveTheHills
savethehills@gmail.com
9475033744

Extreme rainfall event in the Darjeeling-Sikkim Himalayas: 04/05Oct20205 (Part I - 'The Rainfall')

 Thus far, in the SW monsoons of 2025 our region saw a deficiency of rainfall:

Sept2025 was especially dry in Kalimpong and with the monsoons expected to exit our region on 10Oct2025, one did not expect a major rainfall event.
What has been happening, however is that the Bay of Bengal has been inordinately active with bumper to bumper low pressure areas forming and many of them, after moving over land in a north westerly direction reaching as far as Rajasthan leading to excess rain in a normally arid area.

Origin of the extreme rainfall event.
Around the 29Sep2025, I posted a notice in our What's App group 'Hazard Alerts  or HA' stating a LOW was expected (by IMD) in the Bay on 01Oct2025:

The LOW pressure formed as forecast and quickly intensified into a depression by 02Oct2025

The above image was posted in our Whats App group (HA) on 02Oct2025,showing location of the depression, the forecast track and warnings issued by IMD.
An update to the forecast track of the 'deep depression' now showed the storm moving in a 'nearly northward direction' instead of the normally NW direction.

As forecast, the storm (now a well marked LOW) on 03Oct2025, reached parts of east UP (see below) and was almost stationery there until 04Oct2025.

The storm finally started moving as predicted in a NNE direction, heading directly towards Bihar, SHWB (Sub Himalayan W Bengal) and Sikkim at approx 3pm on 04Oct2025 (yesterday), below:

In the top image, do note the density of lightning strikes which were taking place.

Rainfall data
03Oct2025: Despite having a RED warning for heavy rain, our entire region received very little rain. I distinctly recollect that in Kalimpong (my home), it was a densely overcast day which turned stormy around midday but except for some drizzle, there was no precipitation.

 04Oct2025: I was monitoring the Davis Automatic Weather stations in our area and we had light rain from  around midday. At Kalimpong, it started thundering in the late evening and by 7.30pm, the thunder had intensified. Thereafter, the rainfall, lightning and thunder continued thru the night with little or no break

windy.com image of 11pm/04Oct, just when lightning and rain was increasing over our area. The storm had moved from its earlier location and was approaching us from the SW.

Rainfall Intensity at Kalimpong

The above graph showing the rainfall intensity at Kalimpong on 04Oct2025, also shows the duration of the rainfall. Peak intensity of rainfall almost hit 150mm/hr and almost the entire 158mm of rain came down between 8pm and 4am ie 8hrs.

Lightning strikes at 3.30am/05Oct2025. The storm exited our area and continued NE wards about an hour later having killed 23 people.

Rainfall readout from our Davis AWS at Kurseong at 4.13am on 05Oct2025 (today). Kurseong is known to have heavy rainfall and has some very large landslides there. The rainfall from the extreme event was 393mm.

Praful Rao
SaveTheHills
savethehills@gmail.com
9475033744

We will cover the casualties as well as the damage done by one day's rainfall on 04/05Oct2025 in Part II to this post.

About Early Warning Devices viz Doppler Weather Radars (DWRs) and Automatic Weather Stations (AWS)

  

Below is an article from today’s The Statesman that underscores many of the key issues we at 'SaveTheHills' (STH) have been tirelessly raising, writing about, and advocating for over many years:

 

The information about DWRs which I have been able to garner from the internet is as under:

 

As per the above information there are 10 DWRs in the Western Himalayas (RED dots) and ONLY 3 DWRs in the Eastern region (GREEN dots). In this connection, there maybe some conventional (non DWR) older type weather radars about which I could not get information. These will be replaced by DWRs by 2026.
The above information is reproduced below in a map form:

 

Many years ago, I attended an IMD workshop at Baluatar in Gangtok, where I raised the need of a DWR in the Darjeeling-Sikkim Himalayas. I was told that then that a DWR had been earmarked for Sikkim by IMD but as can be seen nothing materialized over the years and now a DWR is being installed in Malda (W Bengal) which will certainly give adequate inputs/warning for North Bengal but may not be effective for the mountainous regions because of signal loss and shadowing.
In this regard, Nepal has 3 weather radars but I could not locate their data and Bhutan has none.
About IMD Automatic Weather Station website
I have already partly covered this in my blog of yesterday but if you try and access the IMD AWS site (http://aws.imd.gov.in:8091/internal/login.php) today, you will be greeted with this sign

 

Whereas just a few months ago, the IMD AWS information for the whole country was freely available for anyone, now it is 'internal information' only available to IMD or government officials.
Each state has a separate password to gain access to weather data of the state.

With the inputs which I have given you, please read 'The Statesman' article again and wonder which direction our early warning systems for the mountains are pointing.

Praful Rao
SaveTheHills
savethehills@gmail.com
9475033744

A Citizens' Initiative: Re -installing a DAVIS VANTAGE VUE AWS (automatic weather station) at Kurseong (Darjeeling District).

Kurseong is a small town in Darjeeling district, which besides the DHR chugging right thru its length, its myriad tea gardens which almost throttle the town, the famous educational institutions many of which are alas in decline, Kurseong also has the HEAVIEST RAINFALL in the Darjeeling and Sikkim Himalaya.
Realizing this SaveTheHills (STH) had installed a DAVIS Vantage Pro 2 AWS, at our staunch member Mr SachinTamang's home at Sudhapa Tol, Kurseong. The equipment gifted to us by a group of UK scientists in 2016, worked well but went way beyond economic repair (remember STH is group of volunteers and funds are ALWAYS scarce 😊?).

WHY DAVIS AWS instead of much cheaper options now available?
Simply because it is a world class equipment which STH has used for almost 10 years and now we have a small network of DAVIS AWS in the Darjeeling- Sikkim region over which we can monitor real time weather information of the region (see map below).
Over the years, STH also has developed technical experience of the equipment and system to trouble shoot much of the minor problems locally and avoid costly travel expenses of bringing in company engineers from Delhi.
In this regard, Sikkim has a humungous number of DAVIS Vantage Vue and some Vantage Pro models the outputs of which are not available to the public. I wonder why?
Also please recollect that from a few months ago, IMD has made their AWS data pass-word protected for each state - I fail to understand why weather data must now be locked up like military secrets!
The HImalayas are extremely prone to violent, extreme weather , the frequency of which are only increasing. In this scenario, I request the IMD to rethink their policy of locking up weather data behind passwords rather than making them available to the public and researchers.

Re- Installation of DAVIS Vantage Vue AWS at Kurseong on 06Aug2025: funding source.
This would not have been  possible without the direct intervention of Ms Jyotsna Sitling (IFS), of Kalimpong who has known about our work for many years.
Early this year, I was delighted to receive her call and informing me that she would donate some funds to STH.
I suggested that perhaps an AWS at Kurseong?? if it fitted her budget??? (Cost of the equipment can be checked with the distributor in Delhi or from me privately).
Despite the stiff cost, she gave me the go ahead straight away. We re-installed the DAVIS AWS at Kurseong again 0n 06Aug2025

Unboxing and checking the AWS at Kalimpong before installation

STH Member Rohan Rao setting up the Vantage Vue AWS at Sudhapa Tol,
Kurseong on 06Aug2025

Screenshot from my phone at 7.26am this morning. Shows all 5 AWS in our region. The newly installed AWS at Kurseong is tick marked in RED at the bottom of the page. The AWS data is updated almost 2-3mins so the info available is always REAL TIME.

How to access the data

1. Download and install the DAVIS WeatherLink app ( from Google Playstore). You may have to sign up after download.

2. Search for the AWS in our region using keywords like
'STH AWS'  ,  'Kalimpong' , 'BSA AWS',  'Todey', 'Pedong' , 'STH Kurseong NEW' , 'Darjeeling'

3. Once you get the appropriate station add it your list by clicking on the green drop down menu.
DAVIS (Weatherlink) has a worldwide network so you can check the realtime weather data of any of the stations (which are online) anywhere in the world.

DEEP GRATITUDE
STH wishes to express our deep gratitude to Dr Jyotsna Sitling (IFS) for donating the AWS equipment.

My personal thanks to Sachin bhai of Sudhapa Tol, Kurseong for allowing us to use his premises for the STH Kurseong AWS for many years now.

Thanks to Rohan who is our self taught trouble shooting agent.

APOLOGIES
I would like to apologize to all our readers for the silence in this blog since Apr2025. It was because I had severe health issues which kept me away from work and from this region for a prolonged period. I am still in the process of recouping as such my posts may be irregular.

Praful Rao
SaveTheHills
savethehills@gmail.com
9475033744

Photo - essay on 'The Teesta Valley GLOF Disaster - the unheard voices' featured in Social Documentary Network.

'Social Documentary Network (SDN), founded in 2008, is a global community of documentary photographers, editors, curators, NGOs, students, journalists and others who believe in the power of visual storytelling to build understanding and appreciation for the complexities, nuances, wonders, and contradictions that abound in the world today.'

I had uploaded a photo-essay on the landslides in our region ie 'The Silent Disaster' in SDN , way back in 2011 and since then had almost forgotten about it.

A few days ago, I decided to do a story on the Teesta Valley GLOF Disaster focusing mostly on the social impact ie on individuals and communities rather than on the destruction of bridges, dams and other infrastructure.

After curating the photos, writing up captions and so on, I uploaded 17 images onto the SDN website last night which I am glad, to say have been chosen for display.
The exhibit is 'LIVE' and entitled 'The Teesta Valley GLOF disaster - the unheard voices'

The link to the SDN exhibit is here

I hope this will give the Teesta GLOF Disaster better visibility to a world wide audience.

Do have a look and kindly pass the link to others as well.
The exhibit is best viewed on a laptop in the 'Full Screen' mode.

Praful Rao
SaveTheHills
savethehills@gmail.com
9475033744

(Lack of) Rainfall Data of March 2025 of some towns in Darjeeling - Sikkim Himalaya

 

All data from IMD

 

Sikkim, particularly North Sikkim, typically receives more winter and pre-monsoon precipitation than Darjeeling and Kalimpong districts. This is largely due to western disturbances that the reach higher latitudes, bypassing Darjeeling and Kalimpong.
However, this year, the Darjeeling and Kalimpong districts also experienced an unusual lack of significant pre-monsoon thunderstorm activity. The absence of moisture incursion from the Bay of Bengal contributed to this anomaly.
The resulting dry weather in the lower latitudes has led to severe water shortages in Darjeeling and Kalimpong, coinciding with peak tourist season. Furthermore, the dry conditions have caused numerous forest fires along the Teesta Valley, generating pollution and haze due to smoke.

Drone image of a forest fire in the Teesta Valley (in Sikkim, NE of Melli town) on 04Apr2025 at  9.20pm. These fires are a daily happening all along the valley where tinder dry vegetation catches fire or is set on fire.

The reason why we have not published rainfall data after Oct2024 is that in the ensuing drought like condition, there was absolutely no rainfall and as such no data to publish. Unfortunately, this is becoming the trend in our precipitation pattern.

Praful Rao
SaveTheHills
savethehills@gmail.com
9475033744

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