Qualitative hazard and risk assessment of landslides: a practical framework for a case study in China

Landslides are presented in various types; some of which are unique or completely different from those in other countries due to geological conditions in China. Baoji City in Shaanxi Province, as a study area, is intensely affected by loess slope movements, triggered by directly intensive rainfall and indirectly by human activities. This paper provides a framework for the development of a Geographical Information System-based procedure to qualitatively assess landslide risk at a medium scale of 1: 10,000. For environmental factors affecting landsliding in the study area, erosion of river made great contribution to the occurrence of paleo-slides and old slides, while rainfall and human activities were triggers for the presence of recent landslides. The qualitative susceptibility assessment was studied in terms of slope instability using slope units, and regional-scale hazards were then analyzed by incorporating the type of landslides with susceptibility. From the landslide susceptibility analysis, almost 75% of slopes were classified as high susceptibility, in which five slopes were recently reactivated. It was noted that only 6 old landslides were categorized into high levels of hazard in case of rainfall, after assessment by combining susceptibility with types of landslides. Finally, landslide risk analysis was qualitatively made in an automatic way within the GIS, crossing the hazard map and the map of consequences to property.