Survivors described the terrifying speed and power of the "boulders, sand and thick sludge" that killed hundreds and wiped out villages on the border between Nepal and Tibet.

The numbers alone reflect the scale of the destruction: Hundreds of people are reported dead so far, with over a thousand others missing, and entire towns have been wiped out after floods swept the Himalayan region on the border between Nepal and Tibet on Wednesday. But for the survivors, it is the force of the deluge that haunts them. One minute, their lives were routine. The next, the world turned upside down.

Rajan Khatri, 41, a police officer posted at Syabrubesi, one of the riverside villages worst affected by the floods, said he had received a call around 9:10 a.m. local time from a friend warning him that a massive flash flood was heading downstream. He and his colleagues had no time to react. As soon as he hung up, high waves swept through the police station. The water flung him out of the building, and he lost consciousness.

Smriti Ojha, 17, was getting ready for school in Trishuli, in Nepal's Nuwakot district, when she felt a tremor. Initially, she thought it was an earthquake - not unlike the one in 2015 that destroyed her family's home. She rushed out of the rented house where she lives with her friends. Just as she came out, she saw enormous waves.