How landslide-triggering rainfall conditions vary with geology is unclear. The effects of three different geological conditions (gneiss, GN; granite, GR; sedimentary rock, SR) on variations in intensity–duration (I-D) conditions and rainfall characteristics responsible for initiating shallow landslides were examined using data from 476 landslides in South Korea from 1963 to 2018 and detailed statistical analyses. Results from quantile regression and one-way analysis of variance analyses clearly showed that impermeable SR slopes result in smaller critical rainfall than permeable GN and GR slopes do, indicating a relatively high occurrence exceedance probability and susceptibility to landslides in SR slope. These findings suggest that geological conditions, particularly the relatively high susceptibility of SR slopes, should be considered when establishing rainfall information-based landslide warning criteria for South Korea. Our findings can contribute to the assessment of landslide susceptibility and probability based on geological conditions; however, they should be further investigated through in situ observations.

Seasonal water temperature variations in response to air temperature and precipitation were examined in a forested headwater stream (Yeonyeop stream, YS) and an urban river (Bukhan River, BR) within the same basin. In both sites, precipitation and air/water temperatures were monitored from April to November of 2017 and 2018. The differences between air and water temperatures were 4–6 °C higher in the YS than the BR during the summer and fall seasons. Air temperature and precipitation exhibited seasonal differences with no apparent spatial variations; however, water temperature alone varied both seasonally and spatially. Mean temperature elasticity in the YS was greater than that in the BR, whereas mean precipitation elasticity in the YS was lower than that in the BR. Additionally, temperature elasticity increased with water temperature, whereas precipitation elasticity increased with decreases in water temperature, albeit only during the summer. From an elasticity standpoint, our findings suggest that water temperature in a forested headwater stream is more sensitive to air temperature changes than that in an urban river.