Study On Change Of Thaw Slump Based On Remote Sensing Over The Eboling Ridge In Permafrost Region Of Qilian Mountains

Qilian Mountain is the most important ecological barrier and main water conservation area in northwestern China.The permafrost is seriously degraded and thaw slump are widely developed.Studying the changes in thaw slump of the Qilian Mountains not only has important scientific significance,but also has important ecological and society.significance.This paper takes the thaw slump of the eboling Mountains in Qilian Mountains as the research object.Through historical aerial photographs,satellite images and aerial imagery of UAVs in different periods,combined with field investigations,based on remote sensing and GIS platforms.Research on the spatial distribution and time variation of thaw slump,analysis of the development mechanism and influencing factors of thaw slump.The main results are as follows:(1)Use Object-oriented multi-scale image segmentation and artificial visual interpretation,The extracted thaw slump boundary has high precision.Through remote sensing interpretation and field investigation,it was found that many thaw slumps occurred in the Eboling,with the smallest area Only 64 m~2,the largest 7775 m~2.The development ranges from east to west and from valleys to flat areas.There are mainly three types:branch-shaped,long-shaped,and multi-lingual.Of these,11 have no headwall,4 have headwall,and the height is 2.1-3.6m.(2)The thaw slump of the Eboling Mountains is located in the north aspect of the ice-rich permafrost region with an elevation of 3550~3680 m and a slope of 2~14°,and it is actively developed.This is reflected in an increase in the number of 1969-2017(3-15)and an increase in the area of 1997-2017(7751-25292 m~2).The area growth rate for 1997-2009 was 679.9 m~2/y,2009-2015 was 780.2 m~2/y,and 2015-2017 was2351.3 m~2/y.With the increase of slope and elevation,the development of thaw slump becomes slower,and the northwest to thaw slump develops faster than other directions.Have headwall were faster than none,large-area and early-stage development of thaw slumps are the fastest.(3)According to the variation of the retreat rate of thaw slump,the thaw slump of the Eboling Mountains is divided into four development stages,of which 4 are in the initial development stage(the development in the last five years and the retreat rate is fast),4are in the developing stage(the phase-by-phase retreat rate>0.5 m/y),2 are in an increasingly stable stage(the retreat rate is slowing,and the retreat rate in recent years is<0.2 m/y),and 5 are in the basic stable phase(The rate of retreat was significantly slower,and the rate of retrogression in the past five years was 0).Near thaw slumps are in similar stages.(4)The characterstics of the thaw slump is long term,slowness and periodicity.Climatic conditions,micro-topography,permafrost characteristics,vegetation and soil characteristics are important influencing factors for the development of thaw slump.As the thaw slump occurs in the melting season,the climate impact gradually increases with the increase of melting index and rainfall;the gentle slope is conducive to the development of underground ice,and the permafrost and swamp wetland are interdependent.The higher the ice content,the more moderate the slope(3–8°).The larger the catchment area,the finer the soil particles,the weaker the water permeability,and the faster the development of thaw slump.