Identification of potentially dangerous glacial lakes in the northern Tien Shan

Abstract

Like in many other parts of the world, the glaciers in northern Tien Shan are receding, and the permafrost is thawing. Concomitantly, glacial lakes are developing. Historically, outbursts of these glacial lakes have resulted in severe hazards for infrastructures and livelihood. Multi-temporal space imageries are an ideal means to study and monitor glaciers and glacial lakes over large areas. Geomorphometric analysis and modelling allows to estimate the potential danger for glacial lake outburst floods (GLOFs). This paper presents a comprehensive approach by coupling of remote sensing, geomorphometric analyses aided with GIS modelling for the identification of potentially dangerous glacial lakes. We suggest a classification scheme based on an additive ratio scale in order to prioritise sites for detailed investigations. The identification and monitoring of glacial lakes was carried out semi-automatically using band ratioing and the normalised difference water index (NDWI) based on multi-temporal space imagery from the years 1971 to 2008 using Corona, ASTER and Landsat data. The results were manually edited when required. The probability of the growth of a glacial lake was estimated by analysing glacier changes, glacier motion and slope analysis. A permafrost model was developed based on geomorphometric parameters, solar radiation and regionalised temperature conditions which permitted to assess the influence of potential permafrost thawing. Finally, a GIS-based model was applied to simulate the possibly affected area of lake outbursts. The findings of this study indicate an increasing number and area of glacial lakes in the northern Tien Shan region. We identified several lakes with a medium to high potential for an outburst after a classification according to their outburst probability and their downstream impact. These lakes should be investigated more in detail. Bolch, T., Peters, J., Pradhan, B., Yegorov, A., Buchroithner, M.F., Blagoveshchensky,V. (2011) Geomorphometric analysis and modelling allows to estimate the potential danger for glacial lake outburst floods (GLOFs). This paper presents a comprehensive approach by coupling of remote sensing, geomorphometric analyses aided with GIS modelling for the identification of potentially dangerous glacial lakes. We suggest a classification scheme based on an additive ratio scale in order to prioritize sites for detailed investigations. The identification and monitoring of glacial lakes was carried out semi-automatically using band ratioing and the Normalized Difference Water Index (NDWI) based on multi-temporal space imagery from the years 1971 to 2008 using Corona, ASTER and Landsat data. The results were manually edited when required. The probability of the growth of a glacial lake was estimated by analysing glacier changes, glacier motion, and slope analysis. A permafrost model was developed based on geomorphometric parameters, solar radiation and regionalised temperature conditions which permitted to assess the influence of potential permafrost tha...

Glacial lake outburst flood risk in Himachal Pradesh, India: an integrative and anticipatory approach considering current and future threats

“…For moraine-dammed lakes, further parameters that may be integrated within a more complete large-scale assessment of dam stability and current GLOF hazard include dam geometry and freeboard height (Huggel et al 2004), the steepness of the lake front area (Fujita et al 2013), growth of the lake and associated glacier retreat (Bolch et al 2008), vegetation coverage in the dam area (Allen et al 2009), and permafrost conditions (Bolch et al 2011). However, some of these factors become highly uncertain, or, for dam characteristics, impossible to establish for the modelled future lakes.…”

An approach for estimating the breach probabilities of moraine-dammed lakes in the Chinese Himalayas using remote-sensing data

“…The Himalayas have drawn wide attention in the context of the changing climate (ICIMOD, 2009;Bolch et al, 2012). In addition, the rapid melting of glaciers (glacier retreat) has resulted in the formation and expansion of glacial lakes, giving birth to PDMDLs (Richardson and Reynolds, 2000;Randhawa et al, 2005;Bajracharya et al, 2009;Sakai and Fujita, 2010;Salerno et al, 2012;Benn et al, 2012).…”

“…A weighing scheme of ordering the selected variables after the estimation of hazard potential from highest to lowest has been constructed according to the literature and past MDLOF events (Bolch et al, 2011). In this paper, we establish conversion guidelines so as to quantify the probabilities of components of a breach mode for moraine-dam failure employing the historic performance method combined with expert knowledge and experience.…”

“…To identify PDMDLs in a region, from the view of glacier dynamics, lake type and change, dam characteristics and down-valley status, and guidelines and thresholds for indicating PDMDLs have been comprehensively generalized according to historic MDLOF events (Huggel et al, 2004;McKillop et al, 2007a;Lv et al, 1999). Recently, calculating the breach probability and rating the danger of glacial lakes have been confirmed to be promising approaches, and geostatistics, empirical models, remote sensing and geographic information systems have been put forward to quantify the probability of glacial lake failure in southwestern Pamir, southwestern British Columbia, southeast Tibet and northern Tien Shan (Mergili and Schneider, 2011;McKillop et al, 2007b;Wang et al, 2011;Bolch et al, 2011). However, the available approaches have included limitations when they have been popularized to calculate and rate the breach probability of PDMDLs outside the source region of historic sample MDLOFs, because the guidelines created from the historic sample MDLOFs were characterized by local geographical features (McKillop et al, 2007a).…”

“…(1) The geometry parameters of the dam and parent glacier were obtained from the DEM data produced by aerial-survey topographic maps that are not easy to obtain. Freely available DEMs, such as the ASTER GDEM and the SRTM, have been commonly used to measure glacial lakes and shown to be suitable for a first assessment, but they include inaccuracies (Bolch et al, 2011;Frey et al, 2010;Fujita et al, 2008). High-resolution satellite images such as those taken by SPOT5 (2.5-m resolution in the panchromatic band) and IKONOS (1-m resolution in the panchromatic band) may provide alternative data for the aerial-survey DEMs.…”