Monitoring Of Glaciers Change Along KKH Using Remote Sensing

Karakoram Highway is an international road connecting western China with Pakistan and other countries in West Asia and South Asia,which has very important significance for the countries along the road on the political,economic and cultural aspects.It crosses the Karakoram Mountains,one of the most glaciers concentrated regions,and is being threatened from glaciers along KKH all the time.In order to explore the law of glacier change,many scholars have carried out extensive research on glaciers all over the world.The results show that glaciers in the Karakoram Mountains and other regions in the high Asia region have shown a trend of stabilizing or even increasing glacial material,with most of the world's glaciers shrinking from the effects of global warming.In this paper,the glaciers in the catchment area intersecting KKH and the catchment direction is highway direction are extracted by using the hydrological analysis method of GIS.The study area,bounded by Tajik Autonomous County of Xinjiang Autonomous Region and Kudabad,a town in northern Pakistan,can be roughly divided into three parts: north,South and middle area.In order to extract the data of glacial motion,the velocity of glaciers along the KKH in recent years was obtained by feature-tracking method with Sentinel 1A data covering the study area from Oct.2014 to Nov.2018.The variation of glacier thickness can be estimated by the variation of glacier surface elevation,because the variation of glacier bed elevation is very small in the time range of decades.Therefore,TanDEM published by DLR in 2015 and SRTM DEM published in 2000 have been used to extract the elevation change of glacier surface in the study area.In addition,a pair of TSX/TDX data in February 2015 are used to calculate TanDEM near the Batura sar,it fills in the void in TanDEM in the Batura region.In the interest of analysis of the mass balance of regional glaciers from 2015 to 2018,material balance of glacier was estimated by the height of snow/firn line at the end of the melting period,which was extracted using the difference of backscattering coefficients of different glacial phases in SAR images.The results show that the material balance of glaciers mostly presents a smaller negative value in the study area.Last but not least,the glacial surficial flow speed during 2014 ~ 2018,the glacial surface elevation changes during 2000 ~ 2015 and the elevation of glaciers' snow/firn line of every glacier have been extracted,in order to quantify the threat of each glacier to the KKH and the life of the residents along the KKH.The danger of each glacier and its threat degree to highway were obtained by statistics,according to the different characteristics of glacier surge and glacier flood disasters.Statistical results show that the southern part of the study area,i.e.the glaciers in Pakistan,poses a greater threat to roads than the central and northern parts of the study area.Among the glaciers,glaciers such as Bualtar and Kelayayilake have more possibility of occurrence of glacial flood and debris flow disasters,and the glaciers such as Hasanabad I & II have possibility of glacier surge.