Causes of episodic movement of the Baijiabao landslide based on multiple-time scale analysis

Since the impoundment of the Three Gorges Reservoir (TGR), China, the TGR region has developed numerous landslides, most of which exhibited episodic movement behavior. As a representative example, the Baijiabao landslide in the TGR region is considered herein to investigate the causes of the episodic movement behavior based on multiple-time scale analysis. The cumulative displacements recorded at four manual monitoring sites from 2007 to 2020 and three automatic monitoring sites from 1 November 2017 to 30 August 2020 are collected for the statistical analysis, and multiple-term field investigations are conducted to give insights into the episodic movement of the Baijiabao landslide. Based on geographical detectors, the key individual and combined predisposing factors for the episodic movement corresponding to the monthly, weekly, and daily scales are determined, respectively. The results indicate that the continuous deformation for a dozen of days induces the episodic movement of the landslide at the monthly scale. At the short-time scale, the reservoir water level is a much more significant predisposing factor than rainfall in inducing the deformation of the landslide. At the long-time scale, the episodic movement is greatly affected by both reservoir level and rainfall conditions. In addition, combined predisposing factors consisting of one rainfall-related and one reservoir level–related factor could nonlinearly enhance each other to be better correlated with the landslide deformation.