Budhi Gandaki landslide dam and breach, Gorkha, Nepal
What happened
Early on 11 October 2026 a landslide blocked the Budhi Gandaki river in the upper valley in Gorkha district, Nepal. The landslide dam breached later that morning and a debris flow and flood swept downstream, destroying bridges, homes and a hydropower project camp. Authorities ordered evacuations along the river.
What reports confirm
- Seismic data posted by Kristen Cook records a landslide at 04:22 local time, followed by a breach of the landslide dam at about 6am, which caused the debris flow and flood downstream (The Landslide Blog). (The Landslide Blog)
- Dave Petley suggests from helicopter video that it may have been a rock avalanche; he puts this as a question, not a finding. (The Landslide Blog)
- Five people have probably been killed; houses, roads and bridges were damaged and a camp for the Budhi Gandaki hydropower project was destroyed. Warnings appear to have been disseminated successfully (The Landslide Blog). (The Landslide Blog)
- Authorities ordered evacuations along the Budhi Gandaki on 11 October. No deaths were immediately reported and several people were listed as missing; preliminary accounts said a landslide blocked the river before the temporary barrier gave way (Euronews). (Euronews video)
- The landslide-triggered flash flood swept away bridges and homes in a popular trekking area (weather.com). (weather.com video)
- The two sources give different place names for the landslide (Chumchet in The Landslide Blog, Chumchure in Euronews), so this page uses the upper Budhi Gandaki valley, Gorkha district. (The Landslide Blog, Euronews video)
Cause: Landslide type not confirmed; analysis awaits satellite and aerial imagery.
Likely mechanism, general engineering
General engineering, not a finding about this event
A landslide dam is a pile of loose, ungraded, uncompacted debris with no spillway, no filter and no core, so once the lake rises to the lowest point of the crest the overtopping flow starts eroding the downstream face. Erosion deepens and widens the notch, which lets more water through, which erodes faster, so the outflow can rise from a trickle to a peak in minutes. Seepage through the debris can also cause internal erosion or slope failure of the downstream face before overtopping. How long a dam survives depends on the inflow, the lake volume and what the debris is made of, which is why some last years and this one lasted roughly 90 minutes.