Waves of floodwater came crashing down Nepal’s northernmost river valleys on Wednesday morning, destroying settlements along the way, with Nepalese soldiers joining frantic rescue efforts to find missing people.

Eight bodies were found and 24 people were rescued from different locations, according to Abi Narayan Kafle, a spokesman for the Nepal Police. An unknown number of other people were missing, including the staff at four Nepali Police posts and customs officials stationed at one of the country’s land borders with China, Mr. Kafle said.

Thousands of people live in the riverside settlements downstream from the flooding. The authorities have yet to estimate the number of people missing and the extent of property damage, but said that bridges, schools and hydropower projects had been swept away.

The Independent Power Producers’ Association of Nepal said 14 hydropower projects, including five under construction, have been affected.

“There was no rain in Nepal, so we were not expecting anything like this,” said Narendra Priyar, the chief district officer of Rasuwa, one of the areas affected by the floods.