Abstract
In the Eastern Himalayan Syntaxis region, watershed-scale geological hazards occur frequently, causing significant casualties and infrastructure damage. This study establishes a systematic research methodology from regional scale to individual hazard sites, encompassing the construction of a geological hazard database, identification of hazard chain patterns, dynamic and dam breaching analysis, and risk assessment. The following main achievements were obtained: (1) A total of 175 high-risk river-blocking hazard sites were identified in the lower reaches of the Yarlung Tsangpo River, where watershed-scale hazards are well-developed. Comprehensively considering the geomorphological characteristics of hazard sites, historical hazard events, landslide zoning, and material composition, five typical hazard formation patterns were proposed. InSAR data were also utilized to conduct risk zone identification and assessment for typical hazard sites. (2) A back-analysis was performed on the 2021 large-scale ice-rock avalanche hazard chain event in Sedongpu Gully, with the model and parameters calibrated using seismic ground motion signal records. Results show that the event lasted approximately 300 seconds, with a maximum velocity of approximately 77.2 m/s and a flow thickness of less than 100 m. Through analysis of dynamic processes and mechanical characteristics, the motion stages of the hazard chain and its phase transition processes are better understood. (3) Watershed-scale hazards often lead to river blockage, subsequently forming barrier lakes. For example, the Yigong landslide generated a peak discharge as high as 12.4×10⁴ m³/s, equivalent to 36 times the seasonal flood discharge of the Yigong Zangbo River, and its dam-break flood poses a serious threat to downstream engineering construction. This study provides insights into hazard pattern identification and multi-stage hazard chain dynamic characteristic analysis, and also provides research methodology and technical support for hazard investigation and integrated risk assessment in the Eastern Syntaxis high mountain-canyon region.
Full Text
Preamble
Characteristics of Massive Glacier-Related Watershed Geohazard Chains in the Eastern Himalayan Syntaxis, China
Shaohua Gao
China Institute of Geo-Environment Monitoring (Guide Center of Prevention Technology for Geo-Hazard, MNR), Beijing 100081, China
Abstract
In the Eastern Himalayan Syntaxis region, watershed geohazards occur frequently, causing significant casualties and infrastructure damage. This study establishes a systematic research methodology spanning from regional scale to individual hazard sites, encompassing geohazard database construction, hazard chain pattern identification, dynamic and dam breach analysis, and risk assessment.
First, 175 high-risk river-blocking hazard sites were identified in the lower Yarlung Tsangpo River basin, where watershed hazards are well-developed. By integrating geomorphic characteristics, historical events, landslide zoning, and material composition, five typical hazard formation patterns were proposed, and InSAR data were utilized to conduct risk zone identification and assessment for representative sites.
Second, a back-analysis of the 2021 Sedongpu Gully large-scale ice-rock avalanche hazard chain event was performed, with model parameters calibrated using seismic signal records. Results indicate the event lasted approximately 300 seconds, reached a maximum velocity of about 77.2 m/s, and maintained a flow thickness of less than 100 m. Analysis of dynamic processes and mechanical characteristics enhanced understanding of the hazard chain's motion phases and phase transitions.
Third, watershed hazards frequently cause river blockage and barrier lake formation. For example, the Yigong landslide generated a peak flood discharge of 12.4×10⁴ m³/s, 36 times the seasonal flood discharge of the Yigong Zangbo River, posing severe threats to downstream engineering projects. This study provides insights into hazard pattern recognition and multi-stage hazard chain dynamics, offering methodological and technical support for hazard investigation and integrated risk assessment in the high mountain canyon regions of the Eastern Syntaxis.
Keywords: watershed geohazard chain; hazard formation pattern; ice-rock avalanche; dynamics; barrier lake; Eastern Syntaxis region