Preprints
https://doi.org/10.5194/egusphere-2024-3196
https://doi.org/10.5194/egusphere-2024-3196
08 Nov 2024
 | 08 Nov 2024
Status: this preprint is open for discussion.

Quantifying degradation of the Imja Lake moraine dam with fused InSAR and SAR feature tracking time series

George Brencher, Scott Henderson, and David Shean

Abstract. Glacial lake outburst flood (GLOF) hazards are often tied to the structural properties of the moraines that dam glacial lakes. Traditional investigations of moraine dam structure and degradation involve costly and logistically challenging in-situ geophysical and repeat topographic surveys, which can only be performed for a small number of sites. We developed a scalable satellite remote sensing approach using interferometric synthetic aperture radar (InSAR), InSAR coherence, and SAR feature tracking to precisely measure moraine dam surface displacement and map the extent of buried ice. We combined time series from ascending and descending Sentinel-1 orbits to investigate vertical and horizontal surface displacement from 2017–2024 with ~12-day temporal sampling.

We applied our approach to quantify degradation of the Imja Lake moraine dam in the Everest Region of Nepal. We find that a 0.3 km2 area of the moraine dam has cumulatively subsided ~90 cm over the 7-year study period. Seasonal change in InSAR coherence provides evidence for buried ice throughout the moraine dam. We observe consistent downward and eastward displacement throughout the colder months, which we attribute to ice flow. The magnitude of downward vertical surface velocity increases in the warmer months, likely due to melting of buried ice. Our observations provide new insights into the timing and magnitude of the processes that control moraine dam development and evolution, with broader implications for regional GLOF hazard assessment and mitigation.

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George Brencher, Scott Henderson, and David Shean

Status: open (until 01 Jan 2025)

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George Brencher, Scott Henderson, and David Shean

Model code and software

Fufiters (fused feature tracking-InSAR time series) Scott Henderson and George Brencher https://github.com/relativeorbit/fufiters

George Brencher, Scott Henderson, and David Shean

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Short summary
Glacial lakes are often dammed by moraines, which can fail, causing floods. Traditional methods of measuring moraine dam structure are not feasible for thousands of lakes. We instead developed a method to measure moraine dam movement with satellite radar data and applied this approach to the Imja Lake moraine dam in Nepal. We found that the moraine dam moved ~90 cm from 2017–2024, providing information about its internal structure. These data can help guide limited hazard remediation resources.