Assessment of potential present and future glacial lake outburst flood hazard in the Hunza valley: A case study of Shisper and Mochowar glacier

In Himalayas, new glacial lake formation and expansion of existing glacial lakes have occurred as a consequence of the increasing temperature and glacier recession. These lakes have the potential to release catastrophic volumes of water and trigger a glacial lake outburst flood (GLOF). GLOFs can cause devastating downstream impacts including loss of lives, damage to infrastructure, and economic loss. The risk associated with GLOFs is evident in the case of the Mochowar and the Shisper glaciers of the Hunza valley in the Karakoram ranges. The present study is divided in two parts: 1) investigation of the recent GLOF event from the Shisper glacier ice-dammed lake on 7th May 2022. 2) identification of an overdeepening site for future lake formation at the Mochowar glacier and its future GLOF sus-ceptibility; We used the Himalayan Glacier Thickness Mapper (HIGTHIM) to calculate the thickness of Mochowar gla-cier and identify an overdeepening site at its terminus. This site could host a glacial lake of area 0.22 km2 and a mean depth of 58.97 m that can release a potential flood volume leading to cascading effects with the Shisper ice-dammed lake that further increases the GLOF susceptibility. The GLOF susceptibility of this future lake was determined to be high based on a multi-criterion decision analysis. The recent GLOF event of 7th May 2022 occurred from the Shisper glacier ice-dammed lake. We applied a 2D hydrodynamic model for investigating this GLOF episode and estimated a release volume of 6.23 x 106 m3, with a modelled peak discharge of approximately 1505 m3s-1.

Automated summary

Glacial lake formation and expansion in the Himalayas have resulted from increasing temperatures and glacier recession, posing the risk of glacial lake outburst floods (GLOFs). GLOFs can lead to devastating downstream impacts. The Mochowar and Shisper glaciers in the Hunza valley exemplify the dangers of GLOFs. This study investigates a recent GLOF from the Shisper glacier ice-dammed lake and identifies a potential overdeepening site for future lake formation at the Mochowar glacier. Using the Himalayan Glacier Thickness Mapper (HIGTHIM), a high GLOF susceptibility of the future lake was determined based on multi-criterion decision analysis. The recent GLOF event from the Shisper glacier ice-dammed lake had a estimated release volume of 6.23 x 106 m3.