Overtopping risk of high-hazard embankment dam under climate change condition

These observations are crucial for assessing the potential risks of extreme flooding under different climate change scenarios and designing appropriate flood protection measures for each scenario. The data underscores the significance of considering various climate change projections when evaluating water inflow and planning for resilient infrastructure and flood management strategies. Overtopping failure of embankment dam Fig 25 shows the maximum water level in the reservoir for historical, Early Century, Mid Cen- tury and Late Century compared to designed criteria by USBR in 1981 and previous study of historical data of PMF (Fig 26) by [39] at an initial level 104.85m. The analysis reveals a clear trend of increasing overtopping risks over time, with the severity magnifying under higher RCP scenarios. The early century presents manageable risks, particu- larly under RCP 4.5 and 6.0, where adaptive measures can effectively mitigate potential over- topping. However, RCP 8.5 in the early century already shows significant risks that require immediate attention. In the mid-century, the risks become more pronounced, especially under RCP 6.0 and 8.5. The water pool levels nearing or exceeding the crest level indicate the need for proactive measures, including enhancements to spillway capacity and dam reinforcement. The late century period presents the highest risk, with all scenarios showing significant increases in inflow and outflow. The water pool levels under RCP 8.5 consistently exceed the

crest level, necessitating comprehensive risk management strategies. Structural reinforce- ments, increased monitoring, and emergency preparedness plans are critical to mitigate the severe impacts projected. However, projections for the Early Century (2020–2046) indicate a significant increase in water levels, particularly for higher Average Recurrence Intervals (ARIs). In some scenarios, water levels approach the crest level, suggesting a growing risk of overtopping. This increase can be attributed to the anticipated changes in precipitation patterns and intensities due to cli- mate change. Studies such as those by [35] highlight the need for adaptive strategies to manage these increased risks in the near future. The Mid Century (2047–2073) projections present a more alarming scenario, with several ARI conditions exceeding the crest level, particularly under RCP 6.0 and RCP 8.5 scenarios. This suggests a tangible overtopping risk that could lead to dam failure if not addressed through structural and operational interventions. [31] emphasize the importance of integrat- ing climate projections into dam safety assessments to preemptively mitigate such risks. Looking further into the Late Century (2074–2100), the projections show the highest exceedances of the crest level, with multiple ARI values surpassing it. This period is marked by a severe overtopping risk, especially under the RCP 8.5 scenario, which represents the highest greenhouse gas concentration pathway [31, 35]. The findings by [42] reinforce the critical

need for robust risk-informed decision-making frameworks to enhance the resilience of embankment dams against the increasingly severe impacts of climate change. These projections underscore the urgency for proactive measures, including raising crest levels, enhancing spillway capacities, and adopting comprehensive risk management strategies to ensure the continued safety and functionality of embankment dams in the face of escalating climatic threats The findings from [31, 35] support these trends, indicating that climate change Fig 12. IDF Curve of Mid Century under scenario (a) RCP 4.5, (b) RCP 6.0, and (c) RCP 8.5. Rainfall Intensity vs. Duration for Various Average Recurrence Intervals (ARI), illustrating the decrease in intensity with longer storm durations across different ARI events, ranging from 1-year to 100,000-year return periods. https://doi.org/10.1371/journal.pone.0311181.g012 PLOS ONE Climate change PLOS ONE | https://doi.org/10.1371/journal.pone.0311181 February 27, 2025 21 / 32