Seasonal evaluation of glacier dynamics and risk analysis using remote sensing techniques in the Buni Zom Valley, Chitral River Basin, Northern Pakistan

Abstract

The Hindukush mountain range in northern Pakistan hosts large to medium-sized valley glaciers. These glaciers are continuously retreating due to climate change-induced rising temperatures, leading to erratic discharge and an increasing potential risk to downstream areas. The decadal and annual changes (ablation), snout position, area changes, and associated hazards pose significant risks to downstream communities in the Chitral Valley of the Hindukush Range, northern Pakistan. This study is crucial for understanding the changing dynamics of glaciers and their potential impacts on downstream communities, offering a foundation for developing and implementing evidence-based policies for mitigation and adaptation. This study evaluated glacier risk zones in the Buni Zom valley and the seasonal dynamics of the glacier areas over 28 years (1990–2018) of three glaciers: Khorabhor, Phargam and Gordoghan, using the normalized difference snow index (NDSI) and manual based techniques, utilizing the open-source Landsat images. The Analytical Hierarchy Process (AHP) model was used to identify the risk zones in the study area. The results revealed that the total glacier area is reduced from 16.01% in 1990 to 11.42% in 2018, representing a decline of 4.68%. The highest recession rate was observed between 2015 and 2018, with a 2% loss in the Khorabhor Glacier, 1.5% in the Phargam Glacier, and 0.72% in the Gordoghan Glacier. The glacier snout area receded more at elevations of 3000–4000 m compared to those above 5000 m. The Phargam Glacier, with an area of ≤ 10 km² has receded significantly (4.59%) more than the larger glaciers, such as Gordoghan (≤ 17 km²; 0.09%), and Khorabhor (≤ 15 km²;0.66%). The AHP-based Risk Probability Model showed that the settlements in Phargam Valley, situated 9.7 km from the glacier snout, are at 62.5% risk. The risk arises from the high rate of the glacier recession, resulting in glacial outbursts, water storage in fragile moraine at the terminal area, and increasing the water flow into the Chitral River due to environmental effects. The study is critical to understanding the glacier dynamics in the area, its impacts on the downstream communities and its implications for climate change.