DEVIGHAT, Nepal — Rescue teams searched on Thursday for hundreds of missing people along the Nepal-China border, where a catastrophic and deadly torrent of water and mud several stories high swept through communities a day earlier following a glacier collapse. Videos of the disaster showed people running before the floodwaters swallowed them up and washed out buildings and bridges. At least 353 people were killed, police said, and more than 1,300 are missing, including scores of foreigners and pilgrims. Hundreds others have been displaced across the Himalayan region. The steep slopes and lush valleys below the Himalayan mountain range — home to many of the world’s highest peaks and remaining glaciers — are especially vulnerable to flooding and landslides. Melting glaciers have become more common because of human-caused climate change. Images showed what appeared to be the second floors of buildings in Nepal’s hard-hit Nuwakot district slathered in mud after the torrent rushed by. Debris hung from tree branches and wires, vehicles were buried and some stunned survivors were cak