Hassan, Wajid and Su, Fenghuan and Liu, Weiming and Hassan, Javed and Hassan, Muzammil and Bazai, Nazir Ahmed and Wang, Hao and Yang, Zewen and Garcia-Castellanos, Daniel, Impact of Glacier Changes and Permafrost Distribution on Debris Flows in Badswat and Shishkat Catchments, Northern Pakistan. Available at SSRN: https://ssrn.com/abstract=4204639
Knowledge of glacier changes and associated hazards is of great importance for the safety of the population and infrastructure in the mountainous region of High Mountain Asia. In this study, we assessed the impact of variations in glacier velocity, glacier surface elevation change, meteorological variables, and permafrost distribution on debris flows in Badswat and Shishkat catchments. In Badswat catchment, a debris flow initiated from the former glacial moraine on 17 July 2018. In Shishkat catchment, debris flows usually occur during summer months when air temperatures are highest. We conducted in-depth analyses of long-term in situ meteorological data, field evidence, and satellite images. We applied feature and offset tracking techniques to high-resolution optical and radar images from Landsat, Planet and Synthetic Aperture Radar during 2013–2019 to estimate glacier velocities. We used geodetic methods to estimate glacier surface elevation change. We analyzed the associations between debris flow occurrence, permafrost distribution, and the variations in the 0°C isotherm. Between 1995 and 2019, the increase in temperatures in July is statistically significant for most low- and high-elevation meteorological stations. In Badswat and Shishkat catchments, permafrost is distributed over most of the catchment area and in the debris flow source areas. In Badswat catchment, no significant variations in glacier velocity and elevation change were observed over the study period; however, all three glaciers showed slightly higher velocity toward the terminus during the debris flow events. The debris flow in Badswat catchment damaged infrastructure and blocked the Immit River. The lake created by the blockage of the river inundated 34 houses, a community hall, agricultural land, and other infrastructure such as roads and businesses. Glacier dynamics and seasonal changes in temperature in the permafrost zone could have contributed to debris flow initiation. Our results show that climate and cryosphere change pose significant threats to the population in the region. Monitoring climate and cryosphere change can contribute toward the improvement of disaster risk reduction and mitigation policies.