###### Abstract
Thus, considering the unsaturated soil conditions is essential for natural slopes when evaluating the slope stability and studying the landslide mechanisms subjected to rainfall. Regarding the hazards caused by unexpected rainfall activities due to global warming, the research further investigating the effect of precipitation on slopes increases. A study investigating the effect of climate change on rainfall-induced landslides was published by [PERSON] et al. [17] as a case study in Norway. The study mainly used intensity-duration-frequency calculations and modelled landslides for present and future climate conditions. The future conditions included 10, 50, and 100 years of scenarios. The probability of a landslide initiation (Pf) was found to increase by up to 22.3%, 16.9%, and 13.5% for a given 12 h rainfall event with 10-, 50-, and 100-year return intervals, respectively, due to climate change. [PERSON] et al. [18] investigated the historical rainfall of Singapore from two stations for the period of 1985-2009 and analyzed the rainfalls by duration with linear regression. Regarding the past data, a projection study was carried out, and possible rainfall intensities were determined. Factor of safety values were calculated for projected future data for the years 2003, 2050, and 2100, and a significant decrease was found in the factor of safety data for the increasing years. [PERSON] et al. [19] investigated the importance of geotechnical analysis in the context of climate change adaptation and slope stability. According to the study, the climate change scenarios serve as the foundation for estimating both current extreme precipitation events with a 100-year return period and future extreme precipitation events. Precipitation results in the net infiltration of water, which is dependent upon the prevailing conditions of evaporation, transpiration, and surface water runoff. In conjunction with climate change, the increase in the net infiltration of water might be the most critical parameter to consider. The results of their parametric study demonstrated a significant influence of cohesion on the factor of safety, which exhibits a nearly linear decline of 0.1 for each 1 kPa reduction in cohesion. When the soil permeability is low (<10\({}^{-7}\) m/s), the factor of safety exhibits a downward trend during rainfall and subsequent days. Conversely, when the permeability is higher (k \(\geq\) 10\({}^{-7}\) m/s), the factor of safety displays a decline during rainfall and an upward trend thereafter. The study also indicated that measures to reduce the net infiltration of water would ensure long-term stability, even when considering the potential impact of climate change. The physical and hydrological mechanisms affecting the slope stability were intensively investigated in the study of [PERSON] et al. (2018). The study discussed the strengths and weaknesses of the methods, together with the causes that may have hindered better results for the considered cases. In evaluating the hydrological data, it was emphasized that the type of precipitation and its duration should be carefully considered, with attention paid to aligning the assessment with the successive rainfalls, actual timing, and intensity of the event as well. Previously, the I-D threshold was regarded as a reliable indicator of landslide occurrences triggered by rainfall. However, its effectiveness was limited by its inability to account for antecedent rainfall. Yet, a new I-D threshold was established ([PERSON] et al., 2018) by statistically analyzing hourly rainfall data of landslide occurrences in South Korea for 613 shallow landslides regarding the antecedent rainfall conditions. According to the findings of [PERSON] et al. (2018), even though the heavy rainfall conditions following a dry period were not likely to be found to cause a landslide, a relatively low-intensity rainfall following a wet period did, which pointed to the importance of the antecedent conditions. [PERSON] et al.