## 6 Conclusions  
The Cheyiping landslide project experienced a significant deformation in June 2019, resulting in extensive ground cracking along the reservoir bank, as well as cracking and subsidence of houses and foundations in nearby villages and partial collapse of the riverside road. Through long-term monitoring, field investigations, and theoretical analysis, the study focused on its distribution characteristics, damage features, and the mechanism of ancient landslide reactivation, yielding the following main conclusions:  
(1) Monitoring data from the landslide surface indicates that the rate of deformation during reservoir water level decrease is significantly greater than during water level rise, suggesting a notable impact of water level decrease on the landslide surface. Internal monitoring data reveals pronounced deformations in both shallow and deep layers at the landslide's front, exhibiting a \"circular-arc\" sliding pattern. In contrast, sliding deformations at the rear of the landslide primarily occur in the shallow layers, displaying a \"tilt\" sliding pattern. This suggests that, in this project, the landslide experiences local instability at the front, weakening the support to the rear and leading to traction-type sliding deformation and collapse toward the reservoir bank.  
(2) The correlation analysis of the reservoir water level indicates a strong relationship between the decrease in water level and the cumulative deformation of the landslide. The faster the decrease in reservoir water level, the greater the cumulative deformation of the landslide. In contrast, the correlation between the increase in reservoir water level and the cumulative deformation of the landslide is weaker.  
(3) Numerical simulations reveal that the stability coefficient of the landslide rises with increasing reservoir water levels and falls as they decrease. The primary factor influencing landslide stability is the reservoir water level, while the impact of rainfall on landslide stability is negligible. The rate of change in the landslide's stability coefficient is most pronounced during the initial stages of reservoir water level decline and the final stages of water level rise. Fluctuations in reservoir water levels can induce slope instability, warranting long-term monitoring and inspection of slope deformation. It is advisable that during reservoir management, water levels be lowered gradually, while closely monitoring slope deformation during these periods. If necessary, reinforcement should be applied to the slope's forefront to directly support its rear. Additionally, any cracks on the slope should be promptly filled or fitted with waterproofing membranes and drainage channels to prevent rainwater from infiltrating the sliding zone, despite rainfall not being the direct trigger for the reactivation of ancient landslides in this case.  
In summary, the stability of reservoir bank landslides is closely intertwined with reservoir water levels. The decrease in water levels poses the greatest risk factor for inducing traction-type sliding failures in the ancient Cheyiping landslide, while the influence of rainfall is relatively minor in this project.  
L.D.: Writing--original draft. C.J.: Visualization, Investigation. L.C.: Formal analysis. Q.Z.: Visualization, Investigation. W.C.: Formal analysis. All authors have read and agreed to the published version of the manuscript.  
This work presented in this paper was financially supported by the National Natural Science Foundation of China (Grant No. 52378421).  
Not applicable.  
All data, models, and code that support the findings of this study are available from the corresponding author upon reasonable request.  
Author [PERSON] was employed by the PowerChina Kunming Engineering Corporation Limited. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.