Abstract: Under the influence of water-related disasters, gas transmission pipelines will face significant risks and hazards. Comparing to other geological disasters, water-induced disasters manifest as water-soil coupling processes, accompanied by multi-stage evolutionary processes. To study the impact of water-induced disasters on the reliability of gas transmission pipelines, a pipeline-water-soil model was constructed based on a specific pipeline project. Focusing on the water-induced destruction form of riverbed incision, the Fluent-Rocky module is used for two-way coupling to investigate the formation mechanisms of relevant destruction scenarios. Numerical simulations of river flow erosion are conducted to clarify the three-stage evolution process of riverbed incision buried, exposed, suspended, and multi-physics field analysis of the pipe-soil model is used to determine the characteristics of each stage. Based on specific loading conditions, a multi-scenario mechanical model of the gas transmission pipeline is established. Finite element software ANSYS is used to perform stress analysis for each scenario. Based on the obtain dataset, the specific distribution of random variables is determined, and Monte Carlo sampling is used to calculate reliability changes under multiple scenarios. The study found that in different failure scenarios, the maximum equivalent stress of pipelines in buried and exposed conditions is relatively low, resulting in higher reliability calculated by failure function. However, the maximum equivalent stress in the suspended pipeline stage is relatively higher, leading to lower pipeline reliability.