Glacial Lake Outburst Flood (GLOF) hazards and Geohazards in the Nepal Himalaya

Since 1988, I have been conducting geographical surveys focusing on Imja Glacier Lake in Sagarmatha National Park, one of the dangerous glacial lakes frequently featured in the media. Since 2009, I have collaborated with American researchers (Dr. Alton C. Byers and others) to initiate glacial lake surveys in the Hinku-Hongku Valley of Makalu-Barun National Park. This region hosts a high concentration of glacial lakes, several of which have been identified as hazardous by Nepalese research institutions. From 2009 to 2011, we conducted surveys funded by a grant from the National Geographic Society. Although glacial lakes are often viewed as troublesome, discussions have begun regarding the potential use of drainage from glacial lakes for power generation. To date, this research has been featured in numerous newspapers in Nepal, the UK, and elsewhere.
GLOFs can cause significant impacts downstream when they occur. Our project was selected for one of the J-Rapid projects by JICA immediately after the 2025 earthquake. This involved research in the Dolakha District on the evacuation of downstream residents and the relocation of settlements during GLOF events triggered by earthquakes.

Report of the J-Rapid Project

Watanabe, T. and Paudel, L. (2016) Identification of temporary evacuation sites and relocation of dangerous settlements in the Dolakha District: an approach by hazard mapping.

Padel, L. and Watanabe, T. (2016) Identification of temporary evacuation sites and relocation of dangerous settlements in the Dolakha District: An approach by hazard mapping. J-Rapid Workshop, 21-22 June 2016.

Based on the outcome of the project, we conducted a two-day workshop on ‘Hazard Mapping’ jointly organized by TU, and HU on 23 and 24 June 2016 in order to transfer the methodology of the hazard mapping to Nepal (students of TU).

Publications

Acharya, A., Steiner, J.F., Walizada, K.M., Zakir, Z.H., Ali, S., Gaiserman, A. and Watanabe, T. (2023): Review article: Snow and ice avalanches in high mountain Asia-–scientific, local and indigenous knowledge. Natural Hazards and Earth System Science. https://doi.org/10.5194/nhess-2022-287
Byers, A.C., Shugar, D.H., Chand, M., Portocarrero, C., Shrestha, M., Rounce, D. and Watanabe, T. (2022) Three Recent and Lesser-Known Glacier-Related Flood Mechanisms in High Mountain Environments. Mountain Research and Development, 42(2), A12-A22, https://doi.org/10.1659/MRD-JOURNAL-D-21-00045.1
Thapa, B., Watanabe, T. and D. Regmi (2022): Flood Assessment and Identification of Emergency Evacuation Routes in Seti River Basin, Nepal. Land, 11(1), 82; https://doi.org/10.3390/land11010082
Watanabe, T. (2021) Changes in Glaciers in the High Mountains of South Asia and Their Social Implications. Urushibara, K., Fujitsuka, Y., Matsuyama, H., and Ohnishi, K. (eds.) One-hundred Regional Problems in the World. Nakanishiya Press, 112-113. (In Japanese)
Chand, M.B. and Watanabe, T. (2020): High-resolution inventory of the glacial lakes in the Ngozompa Glacier basin, Everest Region, Nepal. Bulletin of Nepal Hydrogeological Association, Vol. 5, 61-69
Byers, A.C., Chand, M. B., Lala, J., Shrestha, M., Byers, E.A. and Watanabe, T. (2020): Reconstructing the History of Glacial Lake Outburst Floods (GLOF) in the Kanchenjunga Conservation Area, East Nepal: An Interdisciplinary Approach. Sustainability, 12 (13), 5407, https://doi.org/10.3390/su12135407.
Chand, M.B., Watanabe, T. (2019): Development of Supraglacial Ponds in the Everest Region, Nepal, between 1989 and 2018. Remote Sensing, 11 (9), https://doi.org/10.3390/rs11091058.
Khanal, N.R. and Watanabe, T. (2017): Low-flow hydrology in the Nepal Himalayas: the Madi watershed. Geographical Studies, 92 (1), accepted.
Watanabe, T. (2017) Glacial lake outburst flood. In: Suzuki, T., Nogami, M., Sunamura, T. (eds.) “Dictionary of Landforms”, Asakura Publishing, p.744. (in Japanese)]
Watanabe, T., Byers, A.C., Somos-Valenzuela, M.A. and McKinney, D.C. (2016): The need for community involvement in glacial lake field research: The case of Imja Glacial Lake, Khumbu, Nepal Himalaya. In: R. B. Singh, U. Schickhoff, and S. Mal, (Eds.): Climate, Glaciers and Vegetation in Himalaya: Contribution Towards Future Earth Initiatives, Springer International Publishing, 235-250.
Lamsal, D., Sawagaki, T., Watanabe, T., Byers, A.C. and McKinney, D.C. (2015): An assessment of conditions before and after the 1998 Tam Pokhari outburst in the Nepal Himalaya and an evaluation of the future outburst hazard. Hydrological Processes, accepted on 1 August 2015, DOI: 10.1002/hyp.10636.
Watanabe, T. (2015): Interactive comment on “Assessing downstream flood impacts due to a potential GLOF from Imja Lake in Nepal” by M. A. Somos-Valenzuela et al. Hydrol. Earth Syst. Sci. Discuss., 11, C6142-C6144.
Lamsal, D., Sawagaki, T., Watanabe, T. and Byers, A.C. (2014): Assessment of glacial lake development and prospects of outburst susceptibility: Chamlang South Glacier, eastern Nepal Himalaya. Geomatics, Natural Hazards and Risk. DOI: 10.1080/19475705.2014.931306
Byers, A.C., McKinney, D.C., Somos-Valenzuela, M., Watanabe, T. and Lamsal, D. (2013): Glacial lakes of the Hinku and Hongu valleys, Makalu-Barun National Park and Buffer Zone, Nepal. Natural Hazards, accepted. DOI 10.1007/s11069-013-0689-8
Sawagaki, T., Lamsal, D., Byers, A. and Watanabe, T. (2012): Changes in surface morphology and glacial lake development of Chamlang Glacier in the eastern Nepal Himalaya since 1964. Global Environmental Research, 16, 83-94.
Byers, A., McKinney, D., Somos, M. and Watanabe, T. (2012): Glacial lakes of the Hinku and Hongu valleys, Makalu-Barun National Park and Buffer Zone, Nepal. Proceedings, Andean-Asian Mountains Global Knowledge Exchange on Glaciers, Glacial Lakes, Water & Hazard Management An Adaptation Partnership Workshop, 16-32.
Lamsal, D., Sawagaki, T. and Watanabe, T. (2011): Digital Terrain Modelling Using Corona and ALOS PRISM Data to Investigate the Distal Part of Imja Glacier, Khumbu Himal, Nepal. Journal of Mountain Science, 8, 390-402.
Watanabe, T., Lamsal, D. and Ives, J.D. (2009): Evaluating the growth characteristics of a glacial lake and its degree of danger of outburst flooding: Imja Glacier, Khumbu Himal, Nepal. Norsk Geografisk Tidsskrift (Norwegian Journal of Geography), 63, 255-267.
Iyngararasan, M., Li, T., Shrestha, S., Mool, P.K., Yoshino, M. and Watanabe, T. (2004): The Challenges of Mountain Environments: Water, Natural Resources, Hazards, Desertification and the Implications of Climate Change. In Price, M.F., Jansky, L., and Iatsenia, A.A. (eds.) "Key Issues for Mountain Areas", United Nations University Press.
Watanabe, T., Nakamura, N. and Khanal, N.R. (2000): Mountain hazards in the Kanchanjunga area, eastern Nepal: landslides developed on lateral moraines. Journal of Nepal Geological Society, 22, 525-532.
Watanabe, T., Khanal, N.R., and Gautam, M.P. (1998): The Nangama Glacial Lake outburst flood occurred on 23 June 1980 in the Kanchanjunga area, eastern Nepal. Annals of Hokkaido Geographical Society, 72:13-20.
Kattelmann, R. and Watanabe, T. (1998): Approaches to reducing the hazard of an outburst flood of Lmja Glacier Lake, Khumbu Himal. Chalise, S.R. and Khanal, N.R. Eds.: Ecohydrology of high mountain areas. ICIMOD, 359-366.
Kattelmann, R. and Watanabe, T. (1997): Draining Himalayan glacial lakes before they burst. Leavesley, G.H., Lins, H.F., Nobilis, F., Parker, R.S., Schneider, V.R., and van de Ven, F.H.M. Eds.: Destructive water: water-caused natural disasters, their abatement and control. IAHS Publication No. 239, 337-343.
Watanabe, T., Kameyama, S., and Sato, T. (1995): Imja Glacier dead-ice melt rates and changes in a supra-glacial lake, 1989-1994, Khumbu Himal, Nepal: danger of lake drainage. Mountain Research and Development, 15: 293-300.
Watanabe, T., Ives, J.D. and Hammond, J.E. (1994): Rapid growth of a glacial lake in Khumbu Himal, Nepal: prospects for a catastrophic flood. Mountain Research and Development, 14: 329-340.
Yamada, T., Shiraiwa, T., Iida, H., Kadota, T., Watanabe, T., Rana, B., Ageta, Y., and Fushimi, H. (1992): Fluctuations of the glaciers from the 1970s to 1989 in the Khumbu, Shorong and Lagtang regions, Nepal Himalayas. Bulletin of Glacier Research, 10: 11-19.

Selected presentations

Kobayashi Y, Thapa B, Watanabe T, Paudel L, Khanal NR, Ghimire M & Regmi D: Survey on damage in settlements along the Tamakoshi river in Dolakha, Nepal, caused by earthquakes in April/May 2015, Annual Meeting of Japanese Geographers Association, Waseda Univ., Tokyo, March 21, 2016.
Watanabe T, Paudel L, Kobayashi Y, Thapa B, Khanal NR, Ghimire M, & Regmi D: Floods Occurred by a Collapse of an Earthquake-Induced Dam, Gongar, Dolakha, Nepal in April 2015. International Geographical Congress, Beijing, August 22-23, 2016.
Kobayashi Y, Thapa B, Watanabe T, Paudel L, Khanal N, Ghimire M, & Regmi D: Inhabitants’ Awareness of Prevention and Preparation towards Hazards in the Settlements along the Tamakoshi River, Dolakha, Nepal. International Geographical Congress, Beijing, August 22-23, 2016.
Thapa B, Watanabe T & Kobayashi, Y: Risk assessment of flood Hazard in the Nepal Himalaya: Case studies of Seti River, Pokhara and Tamakoshi River, Dolakha. International Geographical Congress, Beijing, August 22-23, 2016.

Related Master's theses and PhD theses supervised

Acharya, A. (2024): An integrated analysis of snow and ice avalanche hazards in the Annapurna Conservation Area, Nepal Himalaya
Bhabana, T. (2022): Flood risk mitigation by inundation mapping and socioeconomic analyses in two river basins of Nepal
Chand, M.B. (2020): Development of glacial lakes in the Everest and Kangchenjunga regions, Nepal Himalaya. PhD thesis submitted to Hokkaido University.
Cui, S. (2020):Distribution and area changes of glacial lakes in Nepal by Sentinel-2. Master's thesis submitted to Hokkaido University.
Liu, W. (2020):The need for community involvement in glacial lake research: a case of Imja Glacial Lake Project, Nepal. Master's thesis submitted to Hokkaido University.
Lamsal, D. (2011): Studies on glacial lake development in the eastern Nepal Himalaya from 1964 to 2010. PhD thesis submitted to Hokkaido University.
Lamsal, D. (2008): A Study of Topographical Changes of the Imja Glacier Lake, Khumbu Himal, Nepal: Prospects for a GLOF Occurrence. Master's thesis submitted to Hokkaido University.

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