Nepal flood triggered by rock and ice avalanche: Report

On October 11, a powerful flash flood struck Nepal's Gorkha district after a huge avalanche of rock and ice broke loose high in the mountains. The flood swept away about 200 houses and five bridges, and left five people missing. Nepal's disaster authority later confirmed that the avalanche, not a simple landslide, caused the sudden and deadly surge of water.

The flood came less than two months after a similar disaster on August 26. That earlier collapse of rock and ice in Rasuwa district created a massive flood that killed more than 1,400 people and left over 5,000 missing. The back-to-back disasters have made officials and scientists very worried about the dangers hidden in Nepal's steep and unstable mountain terrain.

Nepal's National Disaster Risk Reduction and Management Authority studied the October flood carefully. Their report found that the avalanche started in an area with weak rock at about 6,000 meters above sea level. Several smaller landslides also happened nearby, blocking the river for a time before the debris broke apart and the Budhi Gandaki river surged downstream with tremendous force.

The floodwater reached an estimated height of 20 to 25 meters at its peak. That giant wave of water hit and destroyed a hydropower work camp in a place called Salleri. The disaster authority head, Dharam Raj Uprety, said the event was very similar to the deadly August flood in Rasuwa.

Uprety said authorities did receive some early warning of the October flood. That warning allowed them to alert nearby communities before the worst of the water arrived. Because of that alert, officials believe fewer people were hurt or killed than might have been otherwise.

Scientists say that climate change is playing a big role in making these floods more likely and more powerful. As temperatures rise, mountain permafrost — the frozen ground deep inside mountains — begins to thaw. When that happens, rocks and ice that were once held in place can suddenly break free and fall, triggering exactly these kinds of devastating floods.

Nepal's Prime Minister Balendra Shah spoke at the United Nations in September and said the August flooding 'was a warning to the world' about the growing dangers of climate change. Officials now say Nepal urgently needs better systems to monitor its mountains and warn people before disasters strike. They hope that stronger early-warning networks can help save lives the next time a mountain suddenly gives way.