Mountain permafrost and rock glaciers in the dry Andes are of growing interest due to the increase in mining industry and infrastructure development in this remote area. Empirical models of mountain permafrost distribution based on rock glacier activity status and temperature data have been established as a tool for regional-scale assessments of its distribution; this kind of model approach has never been applied for a large portion of the Andes. In the present study, this methodology is applied to map permafrost favourability throughout the semi-arid Andes of central Chile (29–32° S), excluding areas of exposed bedrock. After spatially modelling of the mean annual air temperature distribution from scarce temperature records (116 station years) using a linear mixed-effects model, a generalized additive model was built to model the activity status of 3524 rock glaciers. A permafrost favourability index (PFI) was obtained by adjusting model predictions for conceptual differences between permafrost and rock glacier distribution. The results indicate that the model has an acceptable performance (median AUROC: 0.76). Conditions highly favourable to permafrost presence (PFI ≥ 0.75) are predicted for 1051 km² of mountain terrain, or 2.7 % of the total area of the watersheds studied. Favourable conditions are expected to occur in 2636 km², or 6.8 % of the area. Substantial portions of the Elqui and Huasco watersheds are considered to be favourable for permafrost presence (11.8 % each), while in the Limarí and Choapa watersheds permafrost is expected to be mostly limited to specific sub-watersheds. In the future, local ground-truth observations will be required to confirm permafrost presence in favourable areas and to monitor permafrost evolution under the influence of climate change.

Mountain permafrost and rock glaciers in the dry Andes are of growing interest due to the increase in human activities in this remote area. Empirical models of mountain permafrost distribution based on the spatial analysis of intact and relict rock glaciers and mean annual air temperature (MAAT) have been established as a tool for regional-scale assessments of permafrost favorability across entire mountain ranges; however, this kind of model approach has never been applied for a large portion of the Andes. In the present study, this methodology is applied to map permafrost favorability throughout the semi-arid Andes of central Chile (29° S–32° S), excluding areas of exposed bedrock. After spatially modeling MAAT distribution from scarce temperature records (116 station-years) using a linear mixed-effects model (LMEM), a generalized additive model (GAM) was built to model the activity status of 3524 rock glaciers. A Permafrost Favorability Index (PFI) was obtained by adjusting model predictions for conceptual differences between permafrost and rock glacier distribution. The results indicate that model has an acceptable performance (median AUROC: 0.76). Conditions highly favorable to permafrost presence (PFI ≥ 0.75) are predicted for 1051 km² of mountain terrain, or 2.7 % of the total area of the watersheds studied. Favorable conditions are expected to occur in 2636 km², or 6.8 % of the area. Especially in the Elqui and Huasco watersheds in the northern half of the study area, where a substantial surface portion (11.8 % each) was considered to be favorable for permafrost presence, while predicted favorable areas in the southern Limarí and Choapa watersheds are mostly limited to specific sub-watersheds. In the future, local ground-truth observations will be required to confirm permafrost presence in favorable areas, and to monitor permafrost evolution under the influence of climate change.

Debris flows are rapid downslope movements of soil and rock (a type of external geodynamic process) typically triggered by extreme rainfall, posing significant threats to infrastructure and human lives. The objective of this study is to assess the relationship between rainfall intensity and debris flow magnitude for different return periods (5, 10, 50, and 100 years) and, ultimately, to establish rainfall thresholds in Chasquitambo (Perú). This work presents numerical simulation results for extreme rainfall scenarios using the open-source software HEC-RAS v6.4.1 (Mud/Debris Flow mode), calibrated with flood marks from the recent extreme Cyclone Yaku event that occurred on 12 March 2023 (considered an approximately 100-year event). The simulations reveal a non-linear relationship between rainfall intensity and hazard, with the most extensive impacts reaching velocities of 4.5 m/s, depths of up to 7.0 m, and affecting an area of ~130,000 m². The study indicates an operational rainfall threshold of 20 mm in 24 h, which is proposed to trigger monitoring protocols, early warning systems, and effective mitigation strategies. The proposed workflow provides a transferable and data-efficient foundation for deriving operational rainfall thresholds and scenario-based hazard metrics, which are useful for early warning systems and land-use planning in similar mountain catchments.

Mountain permafrost is an important feature affecting slope stability and hydrological processes, yet its distribution remains poorly understood in many parts of the world, including Chile. This study develops the first countrywide high-resolution (30 m x 30 m) model of mountain permafrost distribution in mainland Chile, using geomorphological evidence from intact (active and inactive) and relict rock glaciers, along with empirical indicators of permafrost presence/absence primarily derived from borehole temperature records, test pits, and surface temperature measurements. We employ a generalized additive model representing local and regional trends by incorporating mean annual air temperature, potential incoming solar radiation, and latitude as predictors. This model achieved an area under the receiver operating characteristic curve (AUROC) of 0.70 (0.74) in spatial (non-spatial) cross-validation. The model's predictions generate a Permafrost Favorability Index (PFI), which expresses the potential of permafrost occurrence conditional on the predictor variables. Excluding glaciers, rock glaciers and vegetated surfaces, areas with PFI values ≥0.75 were classified as having favorable conditions for permafrost development. Under this criterion, approximately 1.06 % (8,042 km²) of mainland Chile exhibits conditions suitable for mountain permafrost, concentrated in the Atacama, Antofagasta, Coquimbo, and Santiago Metropolitan regions (21–32° S and 33–34° S). In contrast, permafrost is scarce or absent from the Maule to the Magallanes regions (south of ~36° S). The interpretation of PFI values should consider local environmental factors not included in the model, such as snow cover duration, clast size, soil properties, and surface albedo. These variables may influence the presence or absence of permafrost locally and should be accounted for using an interpretative guide. This first version of the permafrost distribution model provides a baseline for understanding its general distribution in Chile, which should be refined as new empirical evidence and improved subsurface temperature records become available in the future.

Mountain permafrost is an important feature affecting slope stability and hydrological processes, yet its distribution remains poorly understood in many parts of the world, including Chile. This study develops the first countrywide high-resolution (30 m x 30 m) model of mountain permafrost distribution in mainland Chile, using geomorphological evidence from intact (active and inactive) and relict rock glaciers, along with empirical indicators of permafrost presence/absence primarily derived from borehole temperature records, test pits, and surface temperature measurements. We employ a generalized additive model representing local and regional trends by incorporating mean annual air temperature, potential incoming solar radiation, and latitude as predictors. This model achieved an area under the receiver operating characteristic curve (AUROC) of 0.70 (0.74) in spatial (non-spatial) cross-validation. The model's predictions generate a Permafrost Favorability Index (PFI), which expresses the potential of permafrost occurrence conditional on the predictor variables. Excluding glaciers, rock glaciers and vegetated surfaces, areas with PFI values ≥0.75 were classified as having favorable conditions for permafrost development. Under this criterion, approximately 1.06 % (8,042 km²) of mainland Chile exhibits conditions suitable for mountain permafrost, concentrated in the Atacama, Antofagasta, Coquimbo, and Santiago Metropolitan regions (21–32° S and 33–34° S). In contrast, permafrost is scarce or absent from the Maule to the Magallanes regions (south of ~36° S). The interpretation of PFI values should consider local environmental factors not included in the model, such as snow cover duration, clast size, soil properties, and surface albedo. These variables may influence the presence or absence of permafrost locally and should be accounted for using an interpretative guide. This first version of the permafrost distribution model provides a baseline for understanding its general distribution in Chile, which should be refined as new empirical evidence and improved subsurface temperature records become available in the future.

Mountain permafrost is an important feature affecting slope stability and hydrological processes, yet its distribution remains poorly understood in many parts of the world, including Chile. This study develops the first countrywide high-resolution (30 m x 30 m) model of mountain permafrost distribution in mainland Chile, using geomorphological evidence from intact (active and inactive) and relict rock glaciers, along with empirical indicators of permafrost presence/absence primarily derived from borehole temperature records, test pits, and surface temperature measurements. We employ a generalized additive model representing local and regional trends by incorporating mean annual air temperature, potential incoming solar radiation, and latitude as predictors. This model achieved an area under the receiver operating characteristic curve (AUROC) of 0.70 (0.74) in spatial (non-spatial) cross-validation. The model's predictions generate a Permafrost Favorability Index (PFI), which expresses the potential of permafrost occurrence conditional on the predictor variables. Excluding glaciers, rock glaciers and vegetated surfaces, areas with PFI values ≥0.75 were classified as having favorable conditions for permafrost development. Under this criterion, approximately 1.06 % (8,042 km²) of mainland Chile exhibits conditions suitable for mountain permafrost, concentrated in the Atacama, Antofagasta, Coquimbo, and Santiago Metropolitan regions (21–32° S and 33–34° S). In contrast, permafrost is scarce or absent from the Maule to the Magallanes regions (south of ~36° S). The interpretation of PFI values should consider local environmental factors not included in the model, such as snow cover duration, clast size, soil properties, and surface albedo. These variables may influence the presence or absence of permafrost locally and should be accounted for using an interpretative guide. This first version of the permafrost distribution model provides a baseline for understanding its general distribution in Chile, which should be refined as new empirical evidence and improved subsurface temperature records become available in the future.