Abstract: After the landslide enters the creep deformation stage, it is usually difficult to carry out the investigation and management of the landslide in a timely manner. A reasonable early warning system becomes an important means for effectively reducing landslide hazards. This paper first determined that the key early warning criteria for stepwise landslide induced by rainfall: previous rainfall, current rainfall, and displacement rate. Moreover, one rainfall process is introduced to define the rainfall interval for landslide monitoring, and the warning process is divided into two modes of the previous-current rainfall and the current rainfall. Then the least squares method is used to define the failure inflection point and the stability inflection point on the displacement deformation curve of the stepwise landslide. Thus, the deformation acceleration interval of the landslide is determined to solve the previous rainfall, the current rainfall and the displacement rate threshold. Finally, taking the Wangjiapo landslide as an example, this paper designs the five-level progressive early warning system under two modes. The results show that: (1) the time interval of a rainfall process constituted by the previous rainfall and the current rainfall is 7 days; (2) the displacement rate threshold of Wangjiapo landslide is 20 mm/d; (3) in the mode of the previous-current rainfall, the previous rainfall threshold and the current rainfall threshold of the Wangjiapo landslide are 10 mm and 15 mm, respectively, and the rainfall threshold of the Wangjiapo landslide under the current rainfall mode is 25 mm.

Key words: ‘stepwise’ landslide, one rainfall process, threshold value, early warning system