Multidisciplinary Hazard Mapping Framework for Critical Infrastructure on Terrestrial Permafrost

As the Arctic is warming faster than any other part of the world, Arctic settlements are confronted with growing environmental and socioeconomic pressures while contemplating emerging prospects. In coastal permafrost regions, landscape transformations and permafrost thaw significantly impact local lifestyles and increasingly expose communities to hazards. Changes in the frequency and magnitude of ground subsidence, erosion, and mass wasting events especially threaten the integrity of the built environment. In this context, maintaining functional infrastructure and adapting to rapid changes becomes paramount for the resiliency and sustainable development of Arctic communities.

Building and maintaining infrastructure on permafrost terrains entails many geotechnical and planning challenges. Ensuring permafrost’s mechanical and thermal stability notably requires detailed knowledge of local subsurface conditions and adaptation of construction timing and staging. The adverse effects of poorly adapted designs and practices combined with those of climate change exacerbate permafrost thaw and contribute to the rapid deterioration of the built environment. As a result, infrastructures established on permafrost are already subject to stability issues and at risk of failure under projected climate scenarios. Consequent rehabilitation costs, which are expected to increase and impact already limited local budgets and resources, constitute an additional source of concern.

In regions vulnerable to permafrost thaw, mapping hazards, identifying critical infrastructures, and quantifying the socioeconomic impacts of permafrost thaw is essential. The planning and design of future constructions require improving the characterization of local permafrost conditions and integrating climate predictions. Ultimately, decision support tools are needed at the community scale to support risk management and proactive adaptation strategies.

This study was conducted as part of the work package 6 of the European Horizon 2020 Nunataryuk project, which focused on the impacts of permafrost thaw on coastal arctic infrastructure. The PhD project specifically aimed at developing a multi-disciplinary approach to map permafrost hazards at the community scale and assess infrastructure susceptibility to permafrost thaw.

In order to ensure the applicability of the research outcomes at the local scale, a holistic risk assessment framework was first developed in collaboration with social and health scientists involved in the project. The framework was conceptualized to foster the identification of local concerns and co-design research objectives accordingly.

The settlement of Ilulissat, established on continuous permafrost on the West coast of Greenland, was secondly chosen to apply the framework’s principles. A constant dialogue was maintained with stakeholders throughout the project to shed light on construction and planning challenges currently experienced in the study area. Roads were identified as the infrastructure type most critically affected by permafrost thaw. Therefore, the study focused on producing hazard zonation maps of the road network to support the optimization of maintenance strategies and resources.

As a first step, easily replicable methods for systematically registering road conditions were elaborated. The road network was surveyed in Ilulissat to create high-resolution spatial databases of damages and surrounding hazardous factors. The history of repairs and maintenance operations, as well as associated costs, was reconstructed with stakeholders as a first step to monitor the economic impacts of permafrost thaw on roads. The spatial distribution of damages, repairs, and hazardous factors was then analyzed to identify potential causes for the deterioration of the road network. Sedimentary substrate, water and snow accumulations were found to be spatially correlated with the occurrence of differential thaw settlements. Frequent asphalt resurfacing is currently the primary coping strategy ensuring the serviceability of the road network.

Using these observations in combination with remote-sensing and geotechnical data, a thaw settlement susceptibility index (TSI) was developed to identify road sections at risk from permafrost thaw. A three-class system was used to semi-qualitatively assess the existing road network’s hazards, vulnerability, and severity of impacts. The three main hazard sources previously identified and including the frost-susceptibility of the ground, water, and snow removal accumulations, were characterized as part of the study. To this aim, historical and recent geotechnical data were notably digitized to map the distribution
of different soil types. The average amplitude of seasonal thaw subsidence was secondly derived from the processing of Synthetic Aperture Radar (SAR) images. The geotechnical and remote-sensing information enabled the localization of frost susceptible areas affected by important ground surface deformations and susceptible to the occurrence or aggravation of infrastructure failures. The road networks’ thaw settlement susceptibility was finally evaluated based on the characterization of the hazards, repavement frequency, and observed level of damage. Almost 50 % of the road network surface area currently has a medium to high susceptibility to differential thaw settlements.

This study illustrates how the production of hazard zonation maps, based on the combination of existing datasets, site investigations, remote sensing, and local knowledge, has the potential to support local planning and resource allocation. The research contributed to improving community-scale hazard and risk evaluation capabilities by: i) providing easily reproducible methods for the systematic registration of affected infrastructure and maintenance costs, ii) proposing a multi-disciplinary and comprehensive approach that can be adapted to different site conditions, needs, resource and dataset availabilities.