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