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

Future data hydrograph Early century. Figs 16–18 depict the inflow hydrograph for different return periods (ARIs —Average Recurrence Intervals) ranging from 1 year to 100000 years at the beginning of the century. The graph indicates a trend in the inflow design from scenario RCP 4.5 to RCP 8.5. Furthermore, the comparison of the result with the PMF for each scenario reveals the follow- ing findings: • In the RCP 4.5 scenario, the inflow for ARI 50000 (723.3 m3/s) is greater than the PMF value in RCP 4.5 (572.2 m3/s). • In the RCP 6.0 scenario, the inflow for ARI 50000 (672.4 m3/s) is greater than the PMF value in RCP 6.0 (663.6 m3/s). • In the RCP 8.5 scenario, the inflow for ARI 50 (769.2 m3/s) is greater than the PMF value in RCP 8.5 (642.0 m3/s). This information could be crucial for assessing the risk of extreme flooding and designing appropriate infrastructure or flood protection measures. It also suggests that the RCP 8.5 sce- nario tends to have the highest inflow values for various return periods compared to the other scenarios. Table 4. Intensity duration frequency (IDF) curve parameters for all stations (historical IDF). The parameters Station 3216001- Kg Sg Tua, 3217001- Iby Bekalan KM.16, Station 3317001 Air Terjun Sg Batu, and Station 3317004- Genting Sempah. Rainfall stations/parameters λ κ θ η I 3216001-Kg. Sg. Tua 68.38 0.15 0.29 0.87 55.00 3217001-Ibu Bekalan KM. 16 70.12 0.15 0.24 0.87 58.00 3317001 -Air Terjun Sg. Batu 64.53 0.16 0.25 0.81 54.00 3317004 -Genting Sempah 60.90 0.16 0.28 0.87 49.00

Average 65.98 0.15 0.27 0.85 54.00 https://doi.org/10.1371/journal.pone.0311181.t004 Table 5. Maximum annual rainfall at 1-hr events and the corresponding CCF (corrected future projection). The table provides the Maximum Annual Rainfall at 1 hour (mm) and Climate Change Factor (CCF) for different stations over three time periods (Early Century, Mid Century, Late Century) and under three climate change scenarios (RCP4.5, RCP6.0, and RCP8.5). Station Maximum Annual Rainfall at 1 hr (mm) Early Century Mid Century Late Century RCP4.5 RCP6.0 RCP8.5 RCP4.5 RCP6.0 RCP8.5 RCP4.5 RCP6.0 RCP8.5 3216001 70.38 66.73 153.83 42.33 74.00 153.80 51.00 50.22 153.83 3217001 50.28 53.42 63.98 50.00 49.07 44.68 34.00 56.22 57.04 3317001 70.34 39.22 44.03 42.33 35.90 37.69 51.00 47.58 58.03 3317004 28.39 23.29 28.52 28.25 27.40 31.26 28.00 23.29 34.02 Station Climate Change Factor (CCF) Early Century Mid Century Late Century RCP4.5su RCP6.0 RCP8.5 RCP4.5 RCP6.0 RCP8.5 RCP4.5 RCP6.0 RCP8.5 3216001 1.29 1.22 2.81 1.22 1.35 2.81 0.93 0.92 2.81 3217001 0.87 0.92 1.10 0.92 0.85 0.77 0.59 0.97 0.98 3317001 1.31 0.73 0.82 0.73 0.67 0.70 0.95 0.88 1.08 3317004 0.58 0.47 0.58 0.47 0.56 0.64 0.57 0.47 0.69 Max CCF 1.31 1.22 2.81 1.22 1.35 2.81 0.95 0.97 2.81 https://doi.org/10.1371/journal.pone.0311181.t005 PLOS ONE Climate change PLOS ONE | https://doi.org/10.1371/journal.pone.0311181 February 27, 2025 17 / 32