Reconstructing the process-chain of the 2016 Glacial Lake outburst flood (GLOF), Poiqu basin, Eastern Himalaya
Abstract
Glacial lake outburst floods are a great concern for the Himalayan mountain region, as it can cause substantial damage to the downstream populations and infrastructure. These floods originate at high altitudes as catastrophic waves and can flow down with enormous energy. The consequences are far-reaching with magnitudes that can change the existing morphology of the terrain. One such devastating event occurred on the night of July 5, 2016, from the Gongbatongshacuo Lake, located in the Poiqu basin, Eastern Himalaya. The Poiqu basin currently contains numerous big glacial lakes; however, the 2016 event originated from a small lake located in the Chinese part of the Himalaya. It was a triggered GLOF event that led to the breaching of a damming moraine, completely draining the lake's volume. The flood damaged several infrastructures as it propagated downstream, including the Arniko highway, a hydropower station and several buildings as it made its way into the Bhotekoshi basin in Nepal. It also triggered several small landslides along the banks of the flow channel. In this study, we adopt a multi-model approach to reconstruct the primary and the secondary processes of this 2016 GLOF event. Here, we model the GLOF triggering mechanism from a debris flow event identified from a surrounding slope. Further, we characterize the debris-fall induced impact-wave generated in the lake to determine its failure mechanism. Due to a small freeboard of <5 m, even a little impact could create an overtopping wave, which in this case, was calculated to be slightly <1 m. The reality that even a small overtopping wave may trigger progressive erosion of the damming moraine that can lead to the complete drainage of the lake could be seen in the Gongbatongshacuo Lake. Further, we evaluate the breach-hydraulics and reconstruct the flow hydraulics along the channel using the hydrodynamic model. The GLOF activated several mass movements along the flow path that resulted in landslides. We evaluate the reconstructed GLOF hydraulics at these landslide sites and reconstruct the triggered GLOF-induced landslides using numerical modeling approaches.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMNH006..03S
- Keywords:
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- 1821 Floods;
- HYDROLOGY;
- 4313 Extreme events;
- NATURAL HAZARDS;
- 4333 Disaster risk analysis and assessment;
- NATURAL HAZARDS;
- 4341 Early warning systems;
- NATURAL HAZARDS