## 1 Introduction  
Spanning a total length of 1432 km, the China South-North Water-Diversion Middle-Route Project stands as the largest water-diversion project globally. The project route traverses through a region characterized by complex and diverse geological conditions, including challenging geological engineering factors such as high side slopes, expansive soils, mining areas, and wet sink loess [1, 2, 3]. Particularly, in the elevated canal section near the Danjiangkou Reservoir, a deep excavation construction method was employed to facilitate the implementation of the \"self-flow\" water-transfer approach. Consequently,a deep excavation side slope was formed, which is susceptible to slippage. Additionally, our research has indicated that the slope soil in the canal section belonged to expansive soil, which is prone to swelling and deformation upon exposure to rainwater. Thus, the combination of swelling soil and deep excavation side slope poses a high risk of geological disasters on the channel's side slope. Failure to promptly comprehend the relevant slope-deformation patterns and mechanisms may compromise the overall safety of the project operations [4; 5]. Considering the prevailing soil conditions and construction methods, deformation of deep excavation channel slopes is an inevitable occurrence. The presence of cracks in the lining structure of the channel slope since the commencement of the project indicates an ongoing deformation. However, the current monitoring methods for channel slope deformation in the entire China South-North Water-Diversion Project primarily rely on traditional leveling measurements. These measurements can only detect point deformations at specific measurement points, thus failing to provide a comprehensive understanding of surface area deformations resulting from deep excavation. Furthermore, they do not facilitate the all-weather real-time monitoring of critical deformation areas, significantly limiting our ability to provide an early warning of channel slope-deformation hazards. Clearly, the utilization of traditional leveling measurements does not meet the current demands of channel slope-deformation monitoring. On the other hand, a review of the existing literature highlights a dearth of research regarding the influence of soil moisture content on the three-dimensional deformation of channel slopes in deep excavation sections. This knowledge gap hinders the comprehensive understanding of the slope-deformation mechanism. In recent years, Interferometric Synthetic Aperture Radar (InSAR) interferometry has emerged as a valuable tool for monitoring ground subsidence [6; 7], landslides [8], and other geohazards. With the increasing availability of SAR data, it is now possible to perform long-term monitoring of various targets using historical archives [9; 10; 11]. In particular, InSAR-based methods offer distinct advantages for large-area monitoring tasks such as deformation monitoring of long-distance water-transmission channels. These methods provide extensive spatial coverage and are unaffected by weather conditions such as clouds and rain, making them highly sensitive to ground deformation. [PERSON] et al., [PERSON] et al., [PERSON] et al., and [PERSON] et al. investigated the long-term subsidence law in Mexico using the InSAR technique [12; 13; 14; 15; 16]. [PERSON] et al. deduced the geometry and volume of creep-slide surfaces in the Jinsha River Basin based on InSAR [17]. [PERSON] et al. performed detailed mapping and conducted a kinematic trend assessment of potential landslides associated with large-scale land construction projects using multitemporal InSAR [18]. [PERSON] et al. revealed the complex surface displacement of the Zhouqu Nanyu landslide using multiplatform InSAR observational data [19]. These studies have yielded promising monitoring results, introducing a new technical approach for detecting deformation law in the deep excavation channel section of the South-North Water-Diversion Middle-Route Project.