Hazard Assessment of Collapse and Landslide Disasters in the Upper Reaches of the Dongjiang River Under Different Rainfall Conditions: A Case Study of Sidu Town, Longchuan County, Guangdong Province

It is an urgent need to carry out systematic, detailed, and refined susceptibility assessments in high-risk areas prone to landslides and geological disasters, as well as to conduct risk investigations under different rainfall conditions, to protect the lives and property of local people effectively. This paper takes Sidu Town, Longchuan County, Guangdong Province, as the study area, and utilizes remote sensing images, ground surveys, and regional geological and environmental data to establish a system of landslide disaster susceptibility evaluation indexes by selecting eight influencing factors such as slope gradient, elevation difference, slope shape, cover layer thickness, geotechnical body type, distance from geological structures, vegetation cover index, and land-use types, and applying the informativeness method to assess the susceptibility of Sidu Town to landslide disasters. On this basis, the hazard index method was used to discuss the risk of landslide disaster in Sidu Town under the two working conditions of 24-hour cumulative rainfall of 100 mm rainfall and 24-hour cumulative rainfall of 250 mm rainfall. The result reveals that: (1) The susceptibility of landslide disasters in Sidu Town is predominantly low, covering 65.87% of the total study area, yet 86.23% of landslide disasters are concentrated in the medium susceptibility zone; (2) Under the 24-hour cumulative rainfall of 100 mm scenario, the risk of landslide disasters in Sidu Town is primarily moderate, accounting for 67.86% with an area of 52.71 km²; under the 24-hour cumulative rainfall of 250 mm scenario, the risk of landslide disasters in Sidu Town is primarily high, accounting for 67.51% with an area of 52.44 km². The evaluation system used in this study is deemed highly applicable for assessing the susceptibility to geological disasters in Sidu Town. The evaluation results, validated through field checks, are considered useful and therefore provide a foundation for further geological disaster prevention and control strategies within the region.