India, Aug. 27 -- A wall of muddy water and debris tore through Nepal's Himalayan border region on Wednesday, leaving a trail of destroyed roads, bridges, homes and infrastructure as rescue teams raced to reach people trapped by the sudden disaster. The flood, which struck areas near the Nepal-Tibet border, has also raised concerns in India because the affected rivers eventually feed into the Gandak system.

The disaster has developed into a cross-border emergency. Nepal has reported a rapidly rising death toll and hundreds of missing people, while China has reported casualties and missing people in Tibet. Indian authorities have simultaneously begun preparing for the flood wave moving downstream toward Bihar.

The Indian Meteorological D...