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

input Global Climate Change Model (GCM) model, research was done on rainfall-related extremes along Malaysia’s east coast between 1971 and 2010 compared to the observed period. [21] conducted an assessment of the hydrological conditions that are expected to occur in the future over the Muda and Dungun watersheds in Peninsular Malaysia. In conclusion, every study demonstrates that extreme precipitation patterns in Malaysia are on the rise. In 2019, a study on the effects of climate change on precipitation, temperature, and soil moisture storage was conducted [22]. In conclusion, all studies show rising trends of extreme precipitation in Malaysia. Climate change is expected to affect the hydrological regime and the volume of water flow- ing into reservoirs [23]. Climate change is expected to increase the frequency of heavy rainfall events, which will affect the factors contributing to dam failure [24]. The United States experi- ences an average of 10 dam failures per year, with one of the most severe events being the South Fork Dam disaster induced by significant rainfall [25]. This highlights the global signifi- cance of this issue. Malaysia has also experienced seven dam-related accidents, all attributed to hydrological factors. Notable incidents include the 1970 Panchor Dam failure in Penang, caused by intense rain-induced erosion of upstream slopes, and the 1981 collapse of the Batu Arang Dam in Selangor due to prolonged rains. The Anak Endau Dam in Johor also collapsed in 1986, and a tragic incident occurred at the Sultan Abu Bakar Hydro Power Dam in Pahang

in October 2013, claiming four lives in a water overflow incident [26]. More recently, in March 2021, a flood incident at the Kenyir Dam area in Terengganu caused damage to the flora and fauna [27]. Even if the likelihood of a dam failure is low, the consequences of a failure are enormous, with severe consequences for life, the community, the economy, and the envi- ronment [28]. Dams globally face increased threats of overtopping due to additional loads exceeding their original design capacity. Overtopping is a major concern to dam safety around the world, particularly for embankment dams, because it is the leading cause of dam collapses, which can have disastrous repercussions such as downstream floods and loss of life [29]. Assessing the potential risk of overtopping in embankment dams is crucial given the mag- nitude of the anticipated rise in extreme precipitation events caused by climate change [30]. The occurrence of more frequent and severe floods as a result of climate change in Malaysia poses an increased danger of dam overtopping [27]. This, in turn, might lead to dam failure and raise safety issues for stakeholders involved in water infrastructure [31]. Research has demonstrated that phenomena like variations in water levels and instances of overflowing dur- ing heavy rain can have a substantial effect on the collapse of embankments and their tendency to be overtopped [32]. The current global standards for dam safety mainly deploy statistical or empirical methods, highlighting the importance of better understanding and enhanced safety

assessments in response to hazards induced by climate change [10]. The Intergovernmental Panel on Climate Change (IPCC)’s AR5 Synthesis Report: Climate Change 2014 [10] predicts that the global temperature will surpass 1.5˚C in all RCP scenarios, except RCP2.6, by the end of the 21st century. The IPCC regards RCP 4.5 as a moderate sce- nario, as emissions reach their maximum in approximately 2040 and then decrease. Neverthe- less, it is anticipated that RCP6.0 and RCP8.5 will exceed 2˚C. For instance, in Iran’s Gharesou Basin, climate projections for the period 2040–2069 indicate temperature increases and precip- itation changes of ±30%, resulting in runoff variations ranging from -90% to 120% [33]. Simi- larly, in Sri Lanka’s Nilwala River Basin, future annual streamflow is expected to rise by 59.30% and 65.79% under RCP4.5 and RCP8.5 scenarios, respectively [34]. These projections underscore the heightened risk of overtopping, which can have catastrophic consequences for high-hazard embankment dams. Furthermore, a case study of the Denawaka Ganga mini- hydropower plant in Sri Lanka highlighted some environmental concerns but also significant positive social impacts [32]. Climate change is anticipated to substantially affect water PLOS ONE Climate change PLOS ONE | https://doi.org/10.1371/journal.pone.0311181 February 27, 2025 3 / 32