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Due to warm and humid air currents of the Indian Ocean and the southwest monsoon, the Palong Zangbo catchment in southeastern Tibet has developed oceanic glaciers in the valley, and the activity of glacial debris flows has been gradually intensified under neotectonic activity, frequent earthquakes, climate change, and extreme rainfall. In this paper, the topographic and morphological data of the debris flow basin, the dynamic evolution characteristics of glaciers and glacial lakes were analyzed by using multisource long-term series of remote sensing images. Simultaneously, the distribution of moraines and landslide sources were extracted based on satellite image. In addition, climate change in the study area was analysed using temperature and rainfall data from the last 40 years, revealing that the average temperature in the study area from May to October presented a fluctuating tendency as a whole, especially after 2013, when the temperature gradually increased. As these temperature changes led to continuous melting of the glaciers in the study area, the glacier area decreased from 8,300 km2 in 1988–4,584 km2 in 2019, which decreased nearly 45%. However, the number and area of glacial lakes in the study area gradually increased under a power-law trend, which further led to a significant increase on the possibility of glacial lake rupture in the study area. Due to the joint effects of earthquakes, glacier melting and glacial lake collapse, the debris flows in the study area were well developed, and a total of 122 debris flows were found with varying channel lengths, areas and material sources. Importantly, the characteristics of the glaciers, glacial lakes and climate change in the study area have indicated that the glaciers have retreated, the number of glacial lakes has increased, and the risk of debris flow in this basin will increase in the future. Therefore, it is necessary to strengthen monitoring and early warnings on floods due to glacial lake collapses and debris flows in the study area to improve the risk management of debris flows and floods and the prevention and mitigation of disasters.

Multi-period debris flows have been developed in the last glacial period of the late Pleistocene-Holocene near the Grand Bend of the Yarlung Zangbo River in southeast Tibet, which combined to form a modern large-scale fan-shaped accumulation. The debris flows in the Bangga gully, Pai Town, were explored by ground survey, borehole, and 14C dating methods to investigate the chronological sequence of formation, accumulation depth, and outrush range. The analysis results show that there are still small-scale debris flows in the tributaries of the Bengga gully, and they are widely accumulated in the channel, but no debris flow accumulation has been found in the existing accumulation fan area. The Holocene debris flows in the Bunga gully were active around 8500 years ago, and the cumulative accumulation depth of a single period is about 10.9 m. The two carbon samples in the light gray silt sand formed by the shallow lake facies (fluvial facies) show that the modern riverbed of the Yarlung Zangbo River was deposited at a depth of about 0.4 m in 40 to 100 years, and the annual average deposition rate was about 4~10 mm. The boreholes at 2906.1~2896.7 m and 2849.4~2848.2 m above sea level reveal a thickness of 9.4 m and 1.2 m cake-like bluish-gray clay in turn. It is assumed that two river-blocking events occurred. The above results could provide a reference for the study of the debris flow activity characteristics since the Holocene in this region.

The southwest mountainous region in China is the worst-hit area due to the most developed geohazard chains. In order to better understand the pattern of the geohazard chains in this region, we analyzed the main control factors and characteristics of the geohazard chains based on 19 typical geohazard events in history. Three classification patterns, namely landslide-type, collapse-type, debris flow-type, and five typical hazard-inducing processes, were summarized. A typical hazard-inducing chain process in each model was selected for analysis. On this basis, we discussed the mechanism of the geohazard chain, the construction of a database and technical standard system, and the measures for preventing and controlling transboundary basin chain-type geohazards, aiming to provide a reference for the regional geohazard prevention and mitigation plan, and the major engineering projects' construction and people's safety in town.

On September 5th, 2022, the Ms 6.8 earthquake in Luding County, Sichuan Province induced large numbers of geological hazards. In order to deeply understand the evolution, distribution, and characteristics of geological hazards caused by the earthquake, we obtained the distribution of geological hazards by the field investigation and remote sensing interpretation. The conditions for hazard control and the countermeasures for hazard prevention and reduction are also analyzed. The results show that as of 22:00 on September 14, 2022, the earthquake has induced 565 geological hazards with threat objects in Luding County and Shimian County (including 331 collapses and 234 landslides), and 81 existing geological hazards whose deformation increased. The geological hazards induced by the earthquake are mainly medium and small mass high-level collapses, which are mainly concentrated in the areas with Seismic intensity zone of Ⅸ near the epicenter. These areas include Moxi Town, Detuo Township, both banks of Dadu River between Detuo Township and Dewei town in Luding County, Caoke Township and Wanggangping Township in Shimian County. According to the experience of the Wenchuan earthquake, the debris flow will be active in the next five years, and its characteristics of high frequency and viscous debris flow should be considered in the design of debris flow prevention and control engineering. Under the rainfall condition, the landslide deposition remaining on the slopes of Dadu River banks in the section of Detuo Township—Dewei Town can easily transform into debris flow. The transformation forms of the two hazards’ types should be fully considered in the design of prevention and control projects. The study can provide a reference for earthquake geological hazard prevention and post hazard reconstruction planning in the earthquake area.

Liangshan Prefecture, located at the northeastern edge of the Hengduan Mountain System and within the southern section of the Sichuan-Yunnan tectonic belt in Sichuan Province, China, a region prone to landslides, collapses and debris flows due to its active tectonics, complex topography and significant river erosion. By analysing a dataset of environment factors and geological hazard catalogue, the research uses the Relief algorithm to identify critical influencing factors for each hazard type, selecting 10, 9 and 9 factors for landslides, collapses and debris flows, respectively. Five models are used to assess the vulnerability of these hazards: the Information Value model, the Evidence Weight model, the Logistic Regression model, and both the Evidence Weight-Logistic Regression and the Information Value-Logistic Regression coupled models. The effectiveness of these models is confirmed by confusion matrix and ROC curve analyses, with the combined models showing particularly high accuracy in assessing susceptibility. High risk zones were identified in specific areas and along major fault zones in Liangshan Prefecture. The research provides significant insights into the susceptibility of geological hazards in mountainous and canyon regions, offering a comprehensive approach that goes beyond the limitations of single model applications. This methodology not only provides more accurate and comprehensive results, but also serves as a fundamental reference for geological hazard mitigation and management in Liangshan Prefecture, potentially benefiting similar regions worldwide. [ABSTRACT FROM AUTHOR]