Moraine-dammed glacial lakes and threat of glacial debris flows in South-East Kazakhstan.

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From: Earth-Science Reviews(Vol. 229)
Publisher: Elsevier Science Publishers
Document Type: Report
Length: 416 words

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Keywords Debris flow; Glacial hazard; Glacial lake outburst flood; Hazard mitigation; Moraine-dammed glacial lakes; South-East Kazakhstan Abstract Glacier retreat has caused the emergence of numerous moraine-dammed glacial lakes (MGL) over the last century which have become research foci in many mountain regions of the world. Outbursts of MGLs have caused destructive floods and debris flows, leading to numerous human casualties and significant material damage. The mountains of South-Eastern Kazakhstan have also become prone to lake outburst floods and related debris flows, specifically in the second half of the 20th century. This paper presents and reviews existing surveys and knowledge along with results of own investigations on the formation of MGLs and the characteristics of lake outburst floods and debris flows in the Kazakh part of Tien Shan. We suggest a workflow to identify the most dangerous types of lakes and provide information about their morphogenetic features and hazard criteria. The number of MGLs increased since the 1970s with more than 160 existing in 2018. Forty were identified as being dangerous. Forty-eight lake outbursts occurred since 1950 with all the documented events happened between end of June and end of August. The most dangerous outbursts were caused by ruptures in ice-cored moraine dams. Outbursts of nine MGLs caused disastrous debris flows, with some occurring repeatedly. The number of outbursts decreased since the year 2000 compared to 1970--2000. However, due to ongoing glacier retreat new lakes are forming at higher altitudes. Their greater potential energy makes possible future outbursts more dangerous. Re-evaluation of existing methods to calculate the water volume and peak discharge based on bathymetric measurements and observed outbursts revealed that the applied equations provide suitable approximations and allow supporting mitigation and prevention measures. Finally, the presentation of implemented measures to lower the water level using siphons or artificial flow channels shows that they can reduce the lake outburst hazards. However, they are associated with risks and financial costs and it needs to be carefully considered whether protection measures of the endangered areas are more cost effective. Author Affiliation: (a) Institute of Geography and Water Safety, Almaty, Kazakhstan (b) Al-Farabi Kazakh National University, Almaty, Kazakhstan (c) School of Geography and Sustainable Development, University of St Andrews, Scotland, UK * Corresponding author. Article History: Received 19 December 2020; Revised 24 February 2022; Accepted 15 March 2022 Byline: Akhmetkal R. Medeu (a), Nikolay V. Popov (a), Viktor P. Blagovechshenskiy (a), Maulken A. Askarova (b), Alikhan A. Medeu (a), Sandguash U. Ranova (a), Aidana Kamalbekova (a), Tobias Bolch [tobias.bolch@st-andrews.ac.uk] (c,*)

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Gale Document Number: GALE|A703357064