# Safety Assessment of Gas Pipelines Crossing River through Hydrodynamic Analysis
## 1 Introduction
Previous studies analyzing the safety of gas pipelines using numerical analysis techniques have performed mechanical behavior, pipe diameter, and parameter analyses to explore how gas pipelines are affected by the environment in which they are buried. In the case of gas pipelines buried in rivers, the burial depth has the greatest influence on pipeline exposure, so many countries are evaluating the safety of gas pipelines buried in rivers based on burial depth [2]. In the United States, the pipeline risk management standard of the API (American Petroleum Institute) stipulates the risks and potential damage mechanisms associated with river crossings, as well as lifecycle management and operations [29]. In the United Kingdom, the pipeline standard IGEM/TD/3 (Institution of Gas Engineers and Managers Transmission and Distribution Standard 3) has been established to describe the design of river-crossing pipelines, to assess the likelihood of unexpected accidents and the resulting damage impacts, and to mitigate the identified risks [30]. In Australia, following the pipeline design and installation standard AS (Australia Standards) 2885.1, environmental impact assessments must be conducted for all pipeline routes, and geological and hydraulic investigations should be carried out [31]. In Canada, the pipeline design, installation, and maintenance standard CSA (Canadian Standards Association) Z662-15 (oil and gas pipeline system) explicitly requires pipeline systems, including river crossings, to prepare risk assessments according to the pipeline integrity management program [32]. The Korea Gas Safety Corporation conducts regular safety assessments of gas supply facilities every five years. For the safety assessments of gas pipelines buried in rivers, a hydraulic investigation is performed following guidelines for the hydrodynamic safety assessment of buried pipelines [33]. These international standards highlight the global emphasis on comprehensive risk assessments for river-crossing pipelines, particularly concerning hydrodynamic factors and riverbed changes. However, despite these guidelines, challenges remain in accurately predicting and managing the impacts of hydrodynamic forces on buried pipelines due to complex environmental conditions. Therefore, there is a need for advanced analytical methods and tools that can enhance the safety evaluations of gas pipelines crossing rivers. Our research aims to fill this gap by employing hydrodynamic analysis to assess site-specific river conditions and propose reinforcement measures tailored to the local environmental context, particularly for rivers in Korea. In this context, our research aims to contribute by employing hydrodynamic analysis techniques to assess riverbed changes and analyze the safety issues of gas pipelines buried in rivers from a hydraulic perspective, ultimately proposing reinforcement measures to mitigate the identified risks. In this study, the hydrodynamic analysis tools SMS (Surface-Water Modeling System) [34; 35] and HEC-RAS (Hydrogic Engineering Center--River Analysis System) [36] were used to examine riverbed changes in areas where buried pipelines cross rivers. The safety issues of gas pipelines buried in rivers were analyzed from the hydraulic aspect, and reinforcement measures were proposed. The next section describes the materials and methods used in this study, including the hydrodynamic models and safety assessment procedures. Following that, the results of the long-term and short-term simulations of riverbed changes and their implications for gas pipeline safety are presented. A comprehensive discussion then compares the findings with similar studies and evaluates the implications of the results for future safety standards. Finally, the paper concludes by summarizing the key findings and suggesting areas for future research and practical recommendations for reinforcing the safety of gas pipelines crossing rivers.