When they finally arrived at Lan's village at 1 p.m. Monday, the elderly villagers had been stranded for nearly 24 hours.

"We evacuated 60 people in Nongdai and its neighboring villages over the past two days," said Tu Tietuo, chief of Dahua County's military affairs department who led the rescue work. "Most were empty-nesters, some were disabled, while many others had chronic diseases."

Empty-nesters are the most vulnerable when natural disasters strike. One bed-ridden septuagenarian was swept away by flood waters on Sunday, and is still missing, Tu said.

"While most elderly villagers struggle with mobility issues, many old people just refuse to leave their ancestral homes," he said. "It's essential we provide adequate care for the elderly to keep them safe."

The Ministry of Civil Affairs believes more than half of Chinese households are seniors who live alone without children around. It estimates there will be more than 51 million empty-nesters by the end of this year.

The situation is particularly worrying in the countryside, as the younger generations leave for better-paid jobs in cities.

By the end of 2014, there were about 274 million migrant workers in China, one-fifth of the population.