## 1 Introduction  
Landslides, as the most common natural geohazard type in mountainous areas, often cause heavy economic loss and human casualties [1]. According to the statistical data in the Three Gorges Reservoir Area (TGRA), increasing slope instabilities have occurred since the establishment of the Three Gorges Dam and the official impoundment of the reservoir [2; 3; 4]. As a world-famous example of a human engineering project seriously impacting the surrounding environment, the TGRA provides a perfect scenario for scholars around the word [5]. Since the official impoundment in 2003, over fifteen years of reservoir water level fluctuations have influenced the stress forces redistribution in the reservoir banks, thus fostering instability and mass movements [6]. After the initial rise, the amount of geomorphic movements and landslide occurrences declined each year as the reservoir bank stabilized [7]. Huge amounts of human and monetary resources were injected to carry out a large number of investigations and engineering remedial works in the reservoir bank area, aiming at a full understanding of the reservoir bank stability [8].  
In recent years, the trend of technical innovation and method improvements intensified due to the gradual maturity of advanced technologies, such as ground-based interferometric synthetic aperture radar (InSAR) [9], InSAR [10], and light detection and ranging (LiDAR) [11]. Currently, InSAR has been accepted and widely used in many landslide investigations. Undoubtedly, InSAR is an effective and powerful tool in hazard researches; however, it is still inadequate to study the intricate relationship between deformation and failure simply according to InSAR ground surface deformation analysis results. At present, the applications of InSAR in the geohazard field can be divided into six categories: Hazard identification [12; 13], hazard mapping [14], systematic monitoring (e.g., [15; 16]), prediction and early warning [17], and stability analysis [18] and hazard remedial measures effect inspection [19; 20].  
As the earliest experimental site of landslide InSAR monitoring technology, under the support of the China Geological Survey, corner reflectors were established on the Xintan landslide and Lianziya landslide in the TGRA early from 1999 [21]. For over ten years of technical advancement, more monitoring test sites were set up in representative landslides, such as Shuping landslide and Fanjiaping landslide, etc. hoping to find a reliable InSAR monitoring technique process [3; 22; 23].  
Due to its unique geographic position and geological conditions, large-scale engineering remedial work was conducted in the TGRA. Landslides with engineering remedial work were typically considered to be stable and no longer monitored, which led to an underestimation of the residual risk. Research monitoring the performance of the remedial work also focused on single landslides instead of the large scale of engineering prevention work covering a regional space [19; 20]. To quantitively evaluate the performance of remedial work, researchers carefully selected the evaluation indexes and divided them into five categories according to the fundamental types and hazard prevention features, to build an evaluation index system [24].  
The objective of this work was to study the geohazards, with a special focus on controlled landslides. In particular, the activity relied on the following steps: (i) Large-scale slow-moving landslide mapping to identify the active landslides, employing InSAR-HCA (hotspot and clustering analysis); (ii) single slope-scale landslide deformation analysis combining InSAR time-series analysis, conventional ground monitoring, and field investigation methods; and (iii) landslide engineering remedial work performance evaluation considering its operating conditions and landslide deformation.