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Typhoon-induced rockslide-debris avalanches are among the most dramatic geohazard in coastal mountainous regions, which commonly result in serious casualties and economic loss. In September 2016, typhoon "Catfish" attacked the Su Village in Southeastern China and triggered a devastating rockslide-debris avalanche. The detached mass traveled 1000 m, generated a powerful air blast, and resulted in 27 deaths. In this study, we performed a thorough survey to investigate the avalanche characteristics and damages caused by air blasts. Meanwhile, numerical modeling and video analysis were conducted to investigate the avalanche dynamics and impacts of the air blast. Results indicated that the avalanche movement lasted for approximately 60 s with a maximum velocity of 42 m/s. The entrainment effect greatly enlarged the avalanche volume and extended the avalanche runout. Moreover, the generated air blast indicated a maximum pressure of 2.5 kPa and caused tree breakage beyond the avalanche runout. [ABSTRACT FROM AUTHOR]

On August 10, 2019, typhoon "Lekima" and the associated heavy rainfall triggered a large landslide in Yongjia County, Zhejiang, China. The sliding mass blocked the river, resulted in an air blast and barrier lake disaster chain, and caused 32 deaths. A thorough survey was performed to investigate the characteristics and possible failure mechanisms of the event. The landslide initiation is caused by the combination of rock mass characteristics, wind load, heavy rainfall, and human activities. The presence of roots and cracks in the strongly weathered tuff provides preferential infiltration channels for the rainwater penetration, causing the rapid destabilization of the slope. Furthermore, we used the dynamic model RAMMS and empirical equations to analyze the disaster-causing process of the landslide. Results indicated that the landslide movement lasted for about 30 s with a maximum velocity of 21 m/s. The generated air blast shows a maximum pressure of 1.7 kPa and caused tree breakage on the opposite side of the river. Subsequently, the sliding mass blocked the river and generated a landslide dam with a maximum thickness of about 14 m. Its combination with heavy rainfall led to the rise of the upstream water level and the submersion of houses in the Shanzao village within 20 min. Our work is expected to improve the understanding of typhoon-induced large landslides and promote the risk assessment of this type of geohazard in coastal regions. [ABSTRACT FROM AUTHOR]

Large ice/rock avalanches have been known to generate extremely powerful air blasts capable of causing fatalities and destruction far beyond the runout of the movement mass. Thus, an appraisal of their possible destructive air blast should be considered during the risk assessments. However, much less is known about how avalanche-induced air blasts occur and how destructive they are. Here an existing DEM-CFD coupled method was innovatively employed to quantitatively analyze the initiation and propagation mechanism of the air blast caused by the largest ice-rock avalanche during Nepal's 2015 Gorkha earthquake, and compared the results with some recorded events. Our results highlighted the contribution of valley morphology to air blast generation. Large high-velocity ice/rock avalanches that have an airborne trajectory or a travel path with turning points can suddenly release tremendous energy and more probably cause destructive air blasts. Additionally, the Langtang air blast presented a propagation of 1 km from the avalanche impact point and equivalent destruction to an EF2–EF5 tornado, causing mass casualties. The large impact region and destructive force of avalanche-induced air blasts suggests their disastrous consequences that should provoke assessment of such type of cascading effect during the landslide risk assessment, especially for the long-term sustainability of planned infrastructure in high-altitude regions. [ABSTRACT FROM AUTHOR]

Snow avalanche run-out is controlled by flow regime, which is heavily dependent on snow temperature and water content. Existing avalanche models calculate temperature change and snow melting arising from frictional work, snowcover entrainment and particle collisions, but ignore the influence of the ambient air temperature. Here, we propose an experimentally-based relationship to describe the sensible heat flux between the flowing avalanche and the ambient air. A snow avalanche case study and a sensitivity analysis are performed using the proposed model. Modeling results suggest a marginal contribution of heat to the avalanche core, but one, that nonetheless can have significant effect on avalanche runout. For wet (warm) avalanches, higher air temperature will amplify water lubrication effects, leading to longer avalanche run-out. Warmer air temperatures also influence the behaviour of dry, cold avalanches, as the presence of meltwater increases snow cohesion, restricting the formation of strong powder clouds and reducing the avalanche run-out. Colder air temperatures facilitate the formation of more fluidized powder snow avalanches with long run-out and strong air-blasts. The proposed model quantifies the temperature change in the avalanche and can be included in avalanche hazard assessments in which temperature and flow regime are important elements, including the understanding of air temperature and avalanche flow in a changing climate. [ABSTRACT FROM AUTHOR]

On January 27, 2021, a small-scale loess landslide occurred in Dangchuan Village, Yongjing County, Gansu Province, China. Timely monitoring and warning helped to prevent any casualties. The sliding mass of the Dangchuan landslide fell in two stages with an interval of 24 s and lasted for a total of 31 s. Eventually, the Dangchuan landslide had a descent height of approximately 120 m and a sliding portion stretching approximately 350 m. The landslide volume was approximately 3 × 104 m3. Based on the investigation of different stages of the Dangchuan landslide and the characteristics of the deposition area, the induction of this landslide was attributed to the effect of frozen stagnant water. Following field investigation of the landslide source and crack areas, a potential sliding mass model with a volume of 5 × 104 m3 was obtained via calculation. To predict the disaster scope of potential landslides, we first used DAN3D software to invert this Dangchuan landslide. Then, based on the numerical model parameters obtained from the inversion, the sliding accumulation process of the potential slide mass was simulated. The results showed that the maximum disaster scope of the potential slide mass would be larger than that of the Dangchuan landslide. The new deposit would cover an area of approximately 3.5 × 104 m2, with a thickness in the range of 0–6 m. The new deposition area would expand by approximately 50 m in the long-axis direction compared to the Dangchuan landslide, impacting the houses and roads. The DAN3D prediction results of the disaster scope will help residents in the potential danger zone evacuate in advance, reducing unnecessary damage. [ABSTRACT FROM AUTHOR]

Four repeated ice-rock avalanches occurred in the Amney Machen Mountains between 2004 and 2019, exhibiting both spatial and temporal characteristics of a recurring disaster chain. These events serve as notable examples of large-scale ice-rock avalanche chain disasters in the Qinghai-Tibet Plateau. Integrating multi-source data including remote sensing imaging, meteorological records, and glacier field observations, the geological and climatic characteristics of recurring ice-rock avalanches were characterized. A comprehensive study of the dynamic glacial changes in the region using multiple approaches, including offset-tracking and support vector machine classification, reveals the underlying triggering mechanisms and spatio-temporal evolution of the ice-rock avalanches. To investigate the possible impact of seismic events on the occurrence of repeated ice-rock avalanches, we performed a time-series analysis of the avalanche-prone mass to assess disaster risk. The results suggest that ice-rock avalanches in Amney Machen are caused by long-term climate warming, short-term meteorological fluctuations, glacier retreats, and patterns of ablation rather than earthquakes. Regional warming has culminated in glacier melt and de-buttressing, while freeze–thaw cycles have caused the propagation of stress crevasses and the deterioration of the ice-rock masses. Meltwater and rainfall introduce external driving forces to the ice-rock system, acting to lubricate and soften the bedrock and accelerate glacier sliding. The glacier’s ablation pattern, characterized by significant thinning at its lower part and slight thinning or even localized thickening at the top, has further heightened the hazard of glacial disasters. Our findings reveal the characteristics, triggering mechanisms, and spatio-temporal evolution of typical ice-rock avalanches, providing insights for monitoring and preventing glacial disasters throughout the Qinghai-Tibet Plateau. [ABSTRACT FROM AUTHOR]