Analysis of Topographic and Snowpack Evolution in Debris Flow-Prone Areas of Xinjiang's Alpine Region

This study investigates the Yarkant River basin in Xinjiang’s alpine region using a digital elevation model and cloud-free 500m snow data from MODIS.The region was classified into two zones based on debris flow hazard characteristics:a debris flow-prone zone (very high/high susceptibility) and a non-prone zone (low/very low susceptibility).The geologic conditions and snowpack evolution characteristics of each zone were analyzed.The results show:(1)The primary geological conditions in the debris flow-prone zone are elevations:4 000~5 000m,slopes:8°~20°,and shaded slopes (3.10% of the prone zone).Hazard sites are mainly concentrated in areas with elevations below 3 000 meters,slopes of 8°~20°,and semi-shaded aspects.(2)The snow cover percentage (SCP) in the very high susceptibility zone is the lowest among all zones (average SCP:10.26%) and exhibits the greatest inter-annual variability (largest standard deviation).Conversely,the high susceptibility zone generally has the highest SCP (average SCP:40.52%) with lower inter-annual variability.(3)Snow-covered days (SCD) are longer in the debris flow-prone area (110.6 days) compared to the non-prone area (86.86 days),and both the onset date of snow cover (SCOD) and the start date of snowmelt (SCMD) are earlier in the prone area (SCOD:339.46/342.70DOY;SCMD:97.59/102.46DOY).Both zones show decreasing trends in SCD and SCMD,and an increasing trend in SCOD,with the debris flow-prone area exhibiting more pronounced changes,leading to a longer SCD.This study quantitatively analyzes the topographical and snowpack characteristics of debris flow-prone areas in the Yarkant River basin,providing a foundation for the prevention and management of debris flow disasters in Xinjiang’s alpine mountains;Snowpack characteristics;Topographic variables.