The mountainous terrain and loss of ground cover made Zhouqu County, Gansu Province, which was hit by China's deadliest mudslide in decades on Sunday, vulnerable to flooding and geological disasters, an expert said Wednesday.

"A lingering drought lasting almost 9 months in some local areas and the 2008 Sichuan earthquake that might have loosened the mountainside and caused some cracks are also reasons behind the devastating mudslide," said Tao Qingfa, Deputy Director of the Department of Geological Environment of Ministry of Land and Resources.

He said mudslides are more devastating than floods because they move rapidly and grow in size, carrying with the current trees, houses and cars that stand in the way.

"They move so fast that there is hardly any time left for evacuation," Tao said.

He also said that the country must adopt precautionary measures against such geological disasters, including regular inspections of mountains, evacuations of residents from mudslide-prone areas, building of walls and stronger structures.

Torrential rain on Saturday night prompted an avalanche of sludge and debris to crash down on the county seat of Zhouqu early Sunday morning, ripping many houses off their foundations and tearing multi-story apartment buildings in half.

As of Tuesday afternoon, the death toll from the accident has risen to 702, with 1,042 still missing.