Remote Sensing-based Snow Monitoring And Snowdrift Risk Assessment Of Bangda Grassland In East Tibet

Snowdrift is a unique natural disaster,which is strongly affected by terrain and climate.It often occurs during the snowy season in high latitude or high altitude areas of our country,threatening local traffic and the production and life of residents.This article takes the Bangda grassland in eastern Tibet as the research area.The starting point is to explore the temporal and spatial distribution characteristics of snow cover in the study area and conduct risk assessment of snowdrift disasters.On the basis of field surveys and meteorological data,using multi-source remote sensing image interpretation,GIS spatial analysis,numerical simulation and other methods,interpreting the snow distribution characteristics of the study area and invert the estimation of snow depth.At the same time,the risk assessment of the snowdrift disaster in the study area is carried out,and the main research conclusions are as follows.1.Through snow inversion and statistical analysis,it is found that the snow in the study area is mainly concentrated from October to May of the following year,and the average snow cover area often exceeds 15%.The characteristics of the average snow area in the study area are: winter>spring>autumn>summer,and there are large annual fluctuations.There is a significant negative correlation between snow area and temperature in the study area.Snow cover is mainly distributed in the interval of 4000?5250m above sea level.The average snow area of each elevation interval increases with the increase of altitude.The average snow area in the study area accounts for a larger proportion of the total area of the slope in the northerly direction,with the largest being close to 50%;while in the southerly direction,the proportion is relatively small,with the smallest being only 10%.Through the inversion estimation of the winter snow depth in the study area,the results show that the snow depth is basically in the range of 10?20cm,the maximum snow depth is usually in January,and the maximum snow depth is 18.6cm.Meteorological data show that the annual maximum snow depth in the study area is between 8.1 and 15.7 cm,which is close to the snow inversion results.2.According to the movement mode,the snowdrift is divided into three types: creep,saltation and suspension,among which saltation is the most important way of movement..The movement process is divided into three stages: starting,transportation and accumulation.Each stage is affected by internal and external factors,including natural meteorological factors such as wind speed,wind direction,snowfall,and road environmental factors such as terrain,vegetation,and route direction,These factors work together to affect the physical and mechanical properties of snow and the wind and snow movement at various stages.3.Using the GIS platform and the Analytic Hierarchy Process to evaluate the occurrence risk of snowdrift in the study area.The susceptibility zoning shows that most of the study area belongs to the medium risk level,and the area accounts for more than 90%.The low-risk and high-risk areas are mainly located in higher mountains and lower river valleys,accounting for2.73% and 5.82%,respectively.Taking the roads and proposed railways in the study area as disaster-bearing bodies,three typical sections were selected to evaluate the arrival risk of snowdrift.A numerical simulation method is used to analyze and study the profile wind speed flow field.It is found that due to the topography,the leeward half-cut is more severely affected by snowdrift disasters,and the embankment and half-windward cut are slightly less threatened.The main form of disaster is that snow particles will decelerate and fall and accumulate in the weakened vortex formed near the roadbed,forming road snow resistance and affecting traffic.