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<p>Debris flows rank among mountainous regions' most destructive natural hazards, frequently causing substantial physical, environmental, and economic damages. Their spatial and temporal dynamics and magnitude are largely determined by climate, geology, topography, hydrology, interconnected sediment sources, and human activities. Northern Pakistan has historically been highly susceptible to and has experienced devastating debris flows due to its active tectonics, steep terrain, fragile landscape, and climate. The frequency of these events has increased in recent years due to climate change-induced increasing temperature and changing patterns of precipitation, resulting in human casualties, injuries, infrastructure damage, and economic losses, posing a major challenge to the sustainable development of the already vulnerable mountain communities. Despite frequent occurrences and severe impacts, studies on debris flow assessment in northern Pakistan are limited to preliminary analyses or localized susceptibility mapping, underscoring the need for comprehensive regional-scale evaluations. Therefore, it is essential to identify potential debris flow hazard zones and evaluate their impacts on downstream communities and infrastructure to support the development and implementation of evidence-based risk mitigation and adaptation strategies. This study develops a comprehensive methodology utilizing open-source remote sensing data, extensive field information, and statistical models, for assessing debris flow hazards at the catchment level and evaluate the vulnerability of downstream infrastructure, environment, and communities in District Ghizer, located in the Hindu Kush mountain range of northern Pakistan. Morphometric parameters, hydrological settings, and land cover computed from the Digital Elevation Model (DEM) and satellite images were analyzed using a multi-criteria decision support system to evaluate the susceptibility of catchments to debris flow. The debris flow hazard assessment results show that 23 catchments are very highly prone, and 20 are highly prone to debris flows due to their steep topographic gradients, rainfall exceeding thresholds, and the presence of abundant loose sediments. However, given the lack of historical records of debris flow events and the regional scale approach, the study does not include temporal and intensity evaluations for hazard assessment. The study also assesses the potential impacts of debris flows on various elements at risk, including buildings, roads, populations, forests, and agricultural land, located on the respective alluvial fans. Considering the type, quantity, distribution, economic value, and fragility of hazard-affected elements, the vulnerability of these features to debris flows was assessed in the study. The results reveal that 3,155 (20%) of buildings are very highly vulnerable and 3,470 (22%) are highly vulnerable to debris flow, while 14,425 (12.3%) people are very highly vulnerable and 29,785 (25.4%) are&#xa0;highly vulnerable. The delineated hazard-prone catchments and spatial distribution of the derived risk are vital for local communities for landuse planning, for policymakers in developing and implementing mitigation strategies and adapting to changing risks influenced by climate change.</p>

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Morphometric analysis of debris flow hazard and risk assessment in the mountain terrains of northern Pakistan using remote sensing and field data

  • 期刊论文

  • 发表日期：

    2025年2月26日

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  • Nisar Ali Shah,
  • Muhammad Shafique,
  • Lewis A. Owen,
  • Yaseen AI-Mulla,
  • Yaseen Ullah

摘要

Debris flows rank among mountainous regions' most destructive natural hazards, frequently causing substantial physical, environmental, and economic damages. Their spatial and temporal dynamics and magnitude are largely determined by climate, geology, topography, hydrology, interconnected sediment sources, and human activities. Northern Pakistan has historically been highly susceptible to and has experienced devastating debris flows due to its active tectonics, steep terrain, fragile landscape, and climate. The frequency of these events has increased in recent years due to climate change-induced increasing temperature and changing patterns of precipitation, resulting in human casualties, injuries, infrastructure damage, and economic losses, posing a major challenge to the sustainable development of the already vulnerable mountain communities. Despite frequent occurrences and severe impacts, studies on debris flow assessment in northern Pakistan are limited to preliminary analyses or localized susceptibility mapping, underscoring the need for comprehensive regional-scale evaluations. Therefore, it is essential to identify potential debris flow hazard zones and evaluate their impacts on downstream communities and infrastructure to support the development and implementation of evidence-based risk mitigation and adaptation strategies. This study develops a comprehensive methodology utilizing open-source remote sensing data, extensive field information, and statistical models, for assessing debris flow hazards at the catchment level and evaluate the vulnerability of downstream infrastructure, environment, and communities in District Ghizer, located in the Hindu Kush mountain range of northern Pakistan. Morphometric parameters, hydrological settings, and land cover computed from the Digital Elevation Model (DEM) and satellite images were analyzed using a multi-criteria decision support system to evaluate the susceptibility of catchments to debris flow. The debris flow hazard assessment results show that 23 catchments are very highly prone, and 20 are highly prone to debris flows due to their steep topographic gradients, rainfall exceeding thresholds, and the presence of abundant loose sediments. However, given the lack of historical records of debris flow events and the regional scale approach, the study does not include temporal and intensity evaluations for hazard assessment. The study also assesses the potential impacts of debris flows on various elements at risk, including buildings, roads, populations, forests, and agricultural land, located on the respective alluvial fans. Considering the type, quantity, distribution, economic value, and fragility of hazard-affected elements, the vulnerability of these features to debris flows was assessed in the study. The results reveal that 3,155 (20%) of buildings are very highly vulnerable and 3,470 (22%) are highly vulnerable to debris flow, while 14,425 (12.3%) people are very highly vulnerable and 29,785 (25.4%) are highly vulnerable. The delineated hazard-prone catchments and spatial distribution of the derived risk are vital for local communities for landuse planning, for policymakers in developing and implementing mitigation strategies and adapting to changing risks influenced by climate change.