Impact of glacier changes and permafrost distribution on debris flows in Badswat and Shishkat catchments,Northern Pakistan

Knowledge of glacier changes and associated hazards is of great importance for the safety consideration of the population and infrastructure in the mountainous regions of Upper Indus Basin(UIB).In this study,we assessed the variations in glacier velocity,glacier surface elevation change,meteorological conditions,and permafrost distribution in Badswat and Shishkat catchments located in UIB to access the potential impact on the occurrence of debris flow in both catchments.We find that the glacier surface velocity increased during the debris flow event in the Badswat catchment and the mean daily temperature was 3.7℃to 3.9℃higher in most of the locations.The enhanced glacier surface elevation lowering period coincide with the rise in temperature during spring and autumn months between 2015 to 2019 in Badswat catchment.The source region of debris flow falls within the lower boundary of permafrost occurrence zone and lies below the 0℃isotherm during late spring and summer months.In Shishkat catchment the 0℃isotherm reaches above the debris flow source area during August and the glacier do not show any significant variations in velocity and surface elevation change.The debris flow source area is adjacent to the slow-moving rock glacier in Shishkat catchment while in Badswat catchment the debris flow initiated from the former glacier moraine.Both catchments are largely glacierized and thus sensitive to changes in climatic conditions and changes in the cryosphere response possess significant threats to the population downstream.Continuous monitoring of cryosphere-climate change in the region can contribute toward the improvement of disaster risk reduction and mitigation policies.

Stability of the Hailuogou glacier during the“9.5”Luding Earthquake:a preliminary assessment based on multi-source observations

On 5th September 2022,a magnitude Ms-6.8 earthquake occurred nearby Mt.Gongga,western Sichuan.The stability of the glaciers in east Mt.Gongga close to the epicenter was widely concerned due to the strong shake triggered by the earthquake.Using multi-source observations(including in-situ photographs,remote sensing datasets before and after the event),we carried out a preliminary assessment of the stability and hazard risks of the Hailuogou(HLG)glacier.Triggered by the earthquake,a small block of fractured ice at the lowest part of icefall collapsed.The magnitude of the coseismic ice avalanche was relatively small,which is comparable in size to most ice avalanches over the past seven years,but much less than the previous mapped largest one(03 April 2018,runout~699 m).One most recent large(runout~608 m)ice avalanche occurred between 01 and 04 September,just before the earthquake,likely unloaded large amount of ice mass and made a larger ice avalanche avoided during the earthquake shake.Nevertheless,the momentum of collapsed snow-icerock mass could be safely unloaded over a wide and gentler-slope ice tongue area,limiting its mobility and the risk of a cascading hazard.Glacier-wide surface flow dynamics monitored by Sentinel-1 satellite SAR time series(12 September 2021–19 September 2022)show that HLG glacier velocity was generally consistent before and after the earthquake.The entire HLG glacier exhibited more stable than expected,with almost no abnormal features detected in its upper accumulation part,the lower ice tongue,and its lateral paraglacial slopes.Since the glacier valley has experienced remarkable downwasting and the paraglacial environment has been strongly disturbed and destabilized,we suggested that,to efficiently evaluate glacier-related cascading hazard risks,it is also necessary to systematically combine multi-source observations(e.g.,high-resolution UAV survey,radar/Lidar scan,ground investigation,monitoring and warning systems)to continuously monitor the regional glacier anomalies in the post-earthquake seismic active areas.