12 Publications

Explore our collection of research papers, technical reports, and field studies on Himalayan hazards and environmental monitoring.

12 publications

13 March 2026· Natural Hazards and Earth System SciencePublished

Advancing glacial lake hazard and risk assessment in Bhutan through hydrodynamic flood mapping and exposure analysis.

Rinzin S, Dunning S, Carr RJ, Allen S, Wangchuk S, Sattar A

Hazard and risk from glacial lake outburst floods (GLOFs) in Bhutan have traditionally been assessed with limited consideration of the downstream exposure and vulnerability associated with individual lakes. However, exposure and vulnerability are key components of risk, and when explicitly attributed to each lake, can provide a more robust basis for prioritising hazard investigations and mitigation efforts. We modelled hypothetical GLOF scenarios for all glacial lakes with an area greater than 0.05 km2 and located within 1 km of a glacier terminus. We then determined GLOF risk by explicitly accounting for downstream impacts using depth–velocity outputs at each exposed element affected by the simulated GLOF from each lake, as well as the vulnerability of the affected community. Our study shows that approximately > 11 000 people, > 2500 buildings, > 250 km of road, > 400 bridges and ∼ 20 km2 of farmland are exposed to potential GLOF in Bhutan. We classified lake130 (Thorthormi Tsho) as a very high hazard glacial lake in Bhutan, five lakes as high hazard and 22 other lakes as moderate hazard. Among these high hazard glacial lakes, three of them: lake93 (Phudung Tsho), lake251, and lake278 (Wonney Tsho) were not recognised as being high hazard in previous studies. Five downstream local government administrative units (LGUs) were associated with very high GLOF risk, while eight others are associated with high GLOF risk. Five of these very high and high risk LGUs had not been previously documented as being at risk from GLOF. Our study underscores the significance of integrating potential inundation mapping and downstream exposure data to define high hazard glacial lakes. We recommend strengthening and expanding the existing GLOF preparedness and risk mitigation efforts in Bhutan, particularly in the LGUs, as having high GLOF risk identified in this study, to reduce potential future damage and loss.

14 November 2025· Journal of GlaciologyPublished

Quantifying heterogeneous glacier dynamics in Lunana, Bhutan, using high-spatiotemporal resolution satellite imagery.

Hyde A , Carr JR, Dunning S, Van Wyk de Vries M

The Lunana region in Bhutan, which hosts four large glacial lakes with significant hazard potential, has undergone rapid changes over the past decade. Using PlanetScope satellite scenes, we mapped ice velocities at monthly intervals from 2017 to 2023. We reveal that the disintegration of Thorthormi Glacier’s terminus in 2022 coincided with year-on-year acceleration with mean surface velocities as high as 448 ±10.0 m a-1 by 2021, and seasonal variability in surface velocity magnitude >144.6 ±10.0 m a-1. This acceleration is attributed to a reduction in basal drag as the terminus reached flotation, evidenced by the calving of tabular icebergs. While Bechung, Raphstreng, and Lugge exhibited a similar interannual velocity trend, the upper regions of Bechung and Raphstreng showed a higher seasonal range (31% and 19.9% from their mean) compared to Lugge (4.2%). In the upper regions we also find a decelerating velocity trend (3.5 – 20.6% over the 6 years), which is attributed to surface thinning and reducing driving stresses. We show that accelerating trends in velocity can be a precursor to higher rates of retreat and rapid lake expansion, demonstrating the importance of continuous monitoring of lake-terminating glacier ice velocities in the Himalaya.

11 July 2025· Bulletin of the American Meteorological SocietyPublished

A Monitoring Network for Mitigating Himalayan Glacial Lake Outburst Floods

Guoqing Zhang, Tandong Yao, Matthias Huss, Jonathan L. Carrivick, Tobias Bolch, Guoxiong Zheng, Menger Peng, Xue Wang, Jakob Steiner, Irfan Rashid, Sonam Rinzin, Sonam Wangchuk, Ashim Sattar, Reet Kamal Tiwari, Duncan Quincey, Faizan Ali

Glacial lake monitoring is urgently needed across the Himalaya due to the threatof glacial lake outburst floods (GLOFs). Furthermore, both the population and the infrastructureexposed to or dependent on these glacial lakes are increasing. However, there are a substantial number of glacial lakes in the Himalaya with potential transboundary GLOF impacts, and their remote, high-altitude locations make monitoring extremely challenging, so existing field measurements are limited. Here, we propose a benchmark Himalayan glacial lake monitoring network“HiGLMN” that will characterize glacial lakes by combining geomorphological signatures ofGLOFs, monitoring triggers and mechanisms of dam failure, and downstream impacts using insitu observations, remote sensing, and hydrodynamic modeling, and feed into early warning for disaster mitigation. We also provide existing practices to support the effectiveness and necessity, and propose strategies for future data management. The monitoring network will contribute to robust GLOF risk management, early warning, and mitigation.

3 June 2025· Natural Hazards and Earth System SciencePublished

Exploring implications of input parameter uncertainties on (GLOF) modelling results using the state-of-the-art modelling code, r.avaflow

Rinzin S, Dunning S, Carr R, Sattar A, Mergili M

Modelling complex mass flow processes, such as glacial lake outburst floods (GLOFs), for hazard and risk assessments requires extensive data and computational resources. Researchers often rely on low-resolution, open-access datasets and parameters derived from plausibility due to the difficulty involved in conducting direct measurements. This results in considerable uncertainties in forward modelling, potentially limiting the accuracy and reliability of predictions. To determine the sensitivity of the model outputs stemming from input parameter uncertainties in the forward modelling, we selected 9 parameters relevant to GLOF modelling and performed a total of 84 simulations, each representing a unique GLOF scenario in the physically based r.avaflow model. Our results indicate that mass-movement-triggered moraine-dammed GLOF modelling outputs are notably sensitive to five parameters, which are, in order of importance: (1) volume of mass movement entering the lake, (2) DEM datasets, (3) origin of mass movement, (4) entrainment coefficient, and (5) basal friction angle. The GLOF output parameter resulting from the volume of mass movement entering the lake has the greatest coefficient of variation (CV) (47 %), while the internal friction angle had the lowest CV (0.4 %). For future GLOF modelling, we recommend carefully considering the output uncertainty stemming from the sensitive input parameters identified here, some of which cannot be constrained before a GLOF and which must be addressed using statistical approaches.

4 November 2024· Journal of GlaciologyPublished

Step-change in supraglacial pond area on Tshojo Glacier, Bhutan, and potential downstream inundation patterns due to pond drainage events

Carr JR, Barrett A, Rinzin S, Taylor C

Climate change is causing Himalayan glaciers to shrink rapidly and natural hazards to increase, whilst downstream exposure is growing. Glacier shrinkage promotes the formation of glacial lakes, which can suddenly drain and produce glacier lake outburst floods (GLOFs). Bhutan is one of the most vulnerable countries globally to these hazards. Here we use remotely sensed imagery to quantify changes in supraglacial water storage on Tshojo Glacier, Bhutan, where previous supraglacial pond drainage events have necessitated downstream evacuation. Results showed a doubling of both total ponded area (104,529 m2 to 213,943 m2) and its standard deviation (64,808 m2 to 158,550 m2) between the periods 1987-2003 and 2007-2020, which was predominantly driven by increases in the areas of the biggest ponds. These ponds drained regularly and have occupied the same location since at least 1967. Tshojo Glacier has remained in the first stage of proglacial lake development for 53 years, which we attribute to its moderate slopes and ice velocities. Numerical modelling shows that pond outbursts can reach between ~6 and 47 km downstream, impacting the remote settlement of Lunana. Our results highlight the need to better quantify variability in supraglacial water storage and its potential to generate GLOFs, as climate warms.

26 February 2023· Journal of HydrologyPublished

GLOF hazard, exposure, vulnerability, and risk assessment of potentially dangerous glacial lakes in the Bhutan Himalaya

Sonam Rinzin, Guoqing Zhang, Ashim Sattar, Sonam Wangchuk, Simon K. Allen, Stuart Dunning, Menger Peng

Deglaciation due to atmospheric warming has led to the formation and expansion of numerous glacial lakes, especially in the eastern Himalaya. Many of these glacial lakes are susceptible to glacial lake outburst floods (GLOFs), which can cause far-reaching impacts on downstream infrastructure and livelihoods. This study is a comprehensive assessment of GLOF susceptibility, hazard, exposure, vulnerability, and risk for four potentially dangerous glacial lakes (Bechung Tsho, Raphstreng Tsho, Thorthomi Tsho, and Lugge Tsho) located in the Lunana glacier complex of the Phochu basin in Bhutan. Exposure and risk assessments were based on modelled GLOF hydrodynamics, infrastructure data, population and housing census data. Among the four glacial lakes, Thorthormi Tsho and Lugge Tsho are relatively more susceptible to outburst floods than Raphstreng Tsho and Bechung Tsho. Outflow flood volumes from these lakes range between 6 × 105 and 3 × 108 m3 which can potentially impact over 16,000 people, two hydropower projects, numerous other infrastructures, and agricultural land up to 150 km downstream of the lakes. The GLOF exposed elements are largely in Punakha and Wangdue Phodrang districts, which are located 90 and 100 km downstream of the Lunana glacier complex respectively. Among 17 subdistrict blocks within the basin, one (Lunana) lies in a very high GLOF risk area, while 9 others are in the high GLOF risk zone. The study highlights the importance of multi-source data in improving the knowledge of downstream GLOF risk and serves as a base for improving GLOF risk reduction strategies in high mountain regions.

7 February 2023· Nature communicationsPublished

Glacial lake outburst floods threaten millions globally

Taylor C, Robinson T, Dunning S, Carr JR, Westoby M

Glacial lake outburst floods (GLOFs) represent a major hazard and can result in significant loss of life. Globally, since 1990, the number and size of glacial lakes has grown rapidly along with downstream population, while socio-economic vulnerability has decreased. Nevertheless, contemporary exposure and vulnerability to GLOFs at the global scale has never been quantified. Here we show that 15 million people globally are exposed to impacts from potential GLOFs. Populations in High Mountains Asia (HMA) are the most exposed and on average live closest to glacial lakes with ~1 million people living within 10 km of a glacial lake. More than half of the globally exposed population are found in just four countries: India, Pakistan, Peru, and China. While HMA has the highest potential for GLOF impacts, we highlight the Andes as a region of concern, with similar potential for GLOF impacts to HMA but comparatively few published research studies.

1 February 2022· Journal of GlaciologyPublished

Spatiotemporal supraglacial pond and ice cliff changes in the Bhutan–Tibet border region from 2016 to 2018

Taylor C, Carr JR, Rounce D

Supraglacial ponds and ice cliffs can dramatically enhance ablation rates on debris-covered glaciers. Supraglacial ponds can also coalesce, forming moraine-dammed lakes at risk of glacial lake outburst flood (GLOF). Given Bhutanese glaciers have some of the highest ice loss rates in the Himalaya and GLOF vulnerability is high, we seek to advance our understanding of the spatial distribution and evolution of supraglacial ponds and ice cliffs. Here, we use high-resolution (3 m) Planet Labs satellite imagery to provide the first short-term, high-resolution dataset of supraglacial pond and ice cliff evolution for three glaciers along the Bhutan–Tibet border from 2016 to 2018. A total of 5754 ponds and 2088 ice cliffs were identified. Large intra-annual changes were observed, with ponded area changes and drainage events coinciding with the seasonality of the Indian Summer Monsoon. On average, ~19% of the total number of ponds had a coincident ice cliff. Pond spatial distribution was driven by ice-surface velocities, with higher numbers of ponds found in areas of low velocity (<8 m a−1). Our study provides the first detailed, quantitative investigation of supraglacial ponds and ice cliffs in Bhutan, providing a framework for further monitoring in this understudied, yet important, region of the Himalaya.

25 November 2021· Frontiers in Earth SciencesPublished

Glacial Lake Area Change and Potential Outburst Flood Hazard Assessment in the Bhutan Himalaya

Sonam Rinzin, Guoqing Zhang, Sonam Wangchuk

Against the background of climate change-induced glacier melting, numerous glacial lakes are formed across high mountain areas worldwide. Existing glacial lake inventories, chiefly created using Landsat satellite imagery, mainly relate to 1990 onwards and relatively long (decadal) temporal scales. Moreover, there is a lack of robust information on the expansion and the GLOF hazard status of glacial lakes in the Bhutan Himalaya. We mapped Bhutanese glacial lakes from the 1960s to 2020, and used these data to determine their distribution patterns, expansion behavior, and GLOF hazard status. 2,187 glacial lakes (corresponding to 130.19 ± 2.09 km2) were mapped from high spatial resolution (1.82–7.62 m), Corona KH-4 images from the 1960s. Using the Sentinel-2 (10 m) and Sentinel-1 (20 m × 22 m), we mapped 2,553 (151.81 ± 7.76 km2), 2,566 (152.64 ± 7.83 km2), 2,572 (153.94 ± 7.83 km2), 2,569 (153.97 ± 7.79 km2) and 2,574 (156.63 ± 7.95 km2) glacial lakes in 2016, 2017, 2018, 2019 and 2020, respectively. The glacier-fed lakes were mainly present in the Phochu (22.63%) and the Kurichu (20.66%) basins. A total of 157 glacier-fed lakes have changed into non-glacier-fed lakes over the 60 years of lake evolution. Glacier-connected lakes (which constitutes 42.25% of the total glacier-fed lake) area growth accounted for 75.4% of the total expansion, reaffirming the dominant role of glacier-melt water in expanding glacial lakes. Between 2016 and 2020, 19 (4.82 km2) new glacial lakes were formed with an average annual expansion rate of 0.96 km2 per year. We identified 31 lakes with a very-high and 34 with high GLOF hazard levels. These very-high to high GLOF hazard lakes were primarily located in the Phochu, Kurichu, Drangmechu, and Mochu basins. We concluded that the increasing glacier melt is the main driver of glacial lake expansion. Our results imply that extending glacial lakes studies back to the 1960s provides new insights on glacial lake evolution from glacier-fed lakes to non-glacier-fed lakes. Additionally, we reaffirmed the capacity of Sentinel-1 and Sentinel-2 data to determine annual glacial lake changes. The results from this study can be a valuable basis for future glacial lake monitoring and prioritizing limited resources for GLOF mitigation programs.

29 July 2020· Science of Remote SensingPublished

Mapping of glacial lakes using Sentinel-1 and Sentinel-2 data and a random forest classifier: Strengths and challenges

Sonam Wangchuk, Tobias Bolch

Glacial lakes pose a serious threat to downstream areas and significantly impact glacier melt. The number and area of lakes has grown in most regions during the last decades due to the ongoing atmospheric warming and retreating glaciers. It is therefore important to identify and monitor these lakes. However, mapping of glacial lakes in alpine regions is challenged by many factors. These factors include the small size of glacial lakes, cloud cover in optical satellite images, cast shadows from mountains and clouds, seasonal snow in satellite images, varying degrees of turbidity amongst glacial lakes, and frozen glacial lake surfaces. In our study, we have developed a fully automated method for mapping glacial lakes across alpine regions including the Python package called “GLakeMap”. The method uses multi-source data such as Sentinel-1 Synthetic Aperture Radar and Sentinel-2 Multi-spectral Instrument data, a digital elevation model, and a random forest classifier model. We use multi-source datasets as inputs for rule-based segmentation of images, mainly aiming at extracting glacial lake objects from satellite images using a set of rules. Segmented objects are then classified either as glacial lake or non-glacial lake objects by the random forest classifier model. The method was tested in eight sites across alpine regions mainly located in High Mountain Asia but also in the Alps and the Andes. We show that the proposed method overcomes a majority of the aforementioned challenges to detect and delineate glacial lakes. The method performs efficiently irrespective of geographic, geologic, and climatic conditions of glacial lakes.

12 February 2019· International Journal of Remote Sensing

Towards automated mapping and monitoring of potentially dangerous glacial lakes in Bhutan Himalaya using Sentinel-1 Synthetic Aperture Radar data

Sonam Wangchuk, Tobias Bolch, Jarosław Zawadzki

The majority of glacial lakes around the world are located in remote and hardly accessible regions. The use of remote sensing data is therefore of high importance to identify and assess their potential hazards. However, the persistence of cloud cover, particularly in high mountain areas such as the Himalayas, limits the temporal resolution of optical satellite data with which we can monitor potentially dangerous glacial lakes (PDGLs). The ability of Synthetic Aperture Radar (SAR) satellites to collect data, irrespective of weather and at day or night, facilitates monitoring of PDGLs by without compromising temporal resolution. In this study, we present a semi-automated approach, based on a radar signal intensity threshold between water and non-water feature classes followed by post-processing including elevations, slopes, vegetation and size thresholds, to delineate glacial lakes in Sentinel-1 SAR images in Bhutan Himalaya. We show the capability of our method to be used for delineating and monitoring glacial lakes in Bhutan Himalaya by comparing our results to 10 m resolution Sentinel-2 multispectral data, field survey data, meteorological data, and a time series of monthly images from January to December 2016 of two lakes. Sentinel-1 SAR data can, moreover, be used for detecting lake surface area changes and open water area variations, at temporal resolution of six days, providing substantial advantages over optical satellite data to continuously monitor PDGLs.

Date Not Available· Journal of Quaternary ScienceIn Review

Reconstructing Past Glacier Extent in the Lunana Region, Bhutan Himalaya

Hope N, Carr JR, King O, Dangal NR, Rinzin S, Davies B

Himalayan glaciers have undergone widespread retreat and mass loss in recent decades, and it is critical to contextualise these contemporary changes within the longer-term record. Here we reconstruct glacier extent from the Late Holocene to present for five glaciers in the Lunana region, Bhutan, using geomorphological evidence and Schmidt hammer dating, and assess satellite era (1974–2024) retreat and thinning by integrating remotely sensed datasets. We identified four moraine-building phases, documenting the transition from a single large valley glacier in the Late Holocene to the five individual glaciers bounded by Little Ice Age (LIA) moraines. We attribute differences in the characteristics of the LIA moraines to topographic controls. Between 1974 and 2024, we observed marked thinning on all five study glaciers, but limited retreat on Glacier A, which remained land-terminating throughout. In contrast, Bechung, Raphstreng and Luggye glaciers underwent rapid proglacial lake expansion and terminus retreat. We suggest that lake bathymetry is a key control on multi-decadal glacier retreat and mass movements may cause interannual frontal position variations, via small scale bathymetric changes. Rapid glacier retreat and lake expansion underscore the need for sustained monitoring of Lunana’s glaciers, to inform hazard assessment, water resource management, and glacier change projections.