Effects of rainfall patterns on occurrence of shallow landslides: a case study in Futian town of Chongqing city

With the intensification of climate change and increasingly frequent rainstorms, rainfall-induced shallow landslides have become a widespread geohazard. However, the influence of rainfall patterns on rainfall-induced landslides is often overlooked compared to other factors like rainfall intensity and accumulative rainfall. This study addresses this gap by using rainfall-induced landslides occurred in Futian Town, Chongqing City in 2014 as a case study to examine how different rainfall patterns (uniform, advanced, delayed, intermediate) affect the occurrence of shallow landslides. The TRIGRS model was applied to calculate the hourly factor of safety (FS) for each pattern, with adjacent FS ≤ 1 indicating potential landslides. Their volumes and occurrence times were estimated based on the failure areas, thickness, and specific hours when FS ≤ 1, and probability density curves were used to quantify differences with rainfall patterns. The results show that advanced rainfall induces the greatest number of shallow landslides but with the smallest volumes, whereas intermediate rainfall induces the largest volumes. Temporally, advanced rainfall leads to the shortest occurrence times, indicating the fastest response to rainfall, whereas delayed rainfall corresponds to the slowest response. These insights are valuable for developing early warning models for rainfall-induced landslides.