Spatiotemporal analysis of Imja Lake to estimate the downstream flood hazard using the SHIVEK approach

Abstract

Climate change is causing glaciers in the Himalayas to recede and shrink. The changing climate is the primary trigger of the expansion of glacial lakes that increases the possibilities of outburst floods (GLOFs) and leads to quantifiable losses such as mortality and damage to populations and infrastructure downstream. Therefore, determining the hazard related to the glacier lakes of the Himalayan region is essential. We have developed an approach named SHIVEK, consisting of the SWIR band thresholding technique and hazard analysis to estimate the possible downstream risk along the GLOF flow path. We examined the spatiotemporal expansion of Imja Lake from 1997 to 2020 using Landsat 5, 7, and 8 data. We employed an automated form of the previously described method based on SWIR band thresholding. The study creates yearly composites from June to September using pre-processed Landsat imageries using a cloud-based platform Google Earth Engine. Our results show a continuous expansion in the geographical area of Imja Lake from 0.81 to 1.56 km2 in 23 years between 1997 and 2020, averaging nearly 0.032 km2 per year. Also, the lake’s area between 2012 and 2020 expanded by 0.26 km2. The overall accuracy of 88.96 ± 6.93% has been achieved for spatiotemporal maps of Imja Lake and intensified confidence in the approach. This study estimates a total of 645 buildings and four bridges that can be impacted due to the outburst of Imja Lake. © 2023, The Author(s) under exclusive licence to Institute of Geophysics, Polish Academy of Sciences & Polish Academy of Sciences.