Hydrodynamic moraine-breach modeling and outburst flood routing - A hazard assessment of the South Lhonak lake, Sikkim

Sattar, A and Goswami, A and Kulkarni, AV (2019) Hydrodynamic moraine-breach modeling and outburst flood routing - A hazard assessment of the South Lhonak lake, Sikkim. In: Science of the Total Environment, 668 . pp. 362-378.

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Abstract

The presence of glacial lakes in the Himalaya makes it a potential mountain hazard, as catastrophic failure of such waterbodies may lead to high-magnitude glacial lake outburst flood (GLOF) events that can cause significant damage to the low-lying areas. The present study evaluates the hazard potential of the South Lhonak lake located in the state of Sikkim, using both one and two-dimensional hydrodynamic modeling approaches. Different breach parameters were calculated based on the lake bathymetry and moraine dimensions. The worst-case GLOF scenario is revealed during an overtopping failure of the moraine, producing a peak flood of 6064.6 m 3 s �1 and releasing a total water volume of 25.7 � 10 6 m 3 . The GLOF hydrograph is routed to calculate peak flood (m 3 s �1 ), inundation depth (m) and flow velocity (ms �1 ) along the main flow channel. The interaction of the flood wave with a major topographic obstruction located 15.6 km downstream of the lake, shows a significant reduction of the flow energy leading to a minimization of the South Lhonak GLOF impact. The flood wave reaches the nearest town Lachen, located at a distance of 46 km downstream from the lake, at 3 h 38 min after the initiation of the breach, with a peak flood of 3928.16 m 3 s �1 and a maximum flow velocity of 13.6 ms �1 . At Chungthang town, located at a distance of 62.35 km from South Lhonak lake, the flood wave potentially inundates settlements along the bank of the flow channel, where a peak flood of 3828.08 m 3 s �1 is reached after 4 h of the initial dam breach event. The study also incorporates modeling of a framework to propose a potential flood remediation measure of the South Lhonak lake GLOF by demonstrating the effect of a lateral inline structure along the flow channel, to check the flow of the potential flood wave. © 2019 Elsevier B.V.

Item Type:	Journal Article
Publication:	Science of the Total Environment
Publisher:	ELSEVIER SCIENCE BV
Additional Information:	cited By 0
Keywords:	Channel flow; Flow velocity; Glacial geology; Hazards; Hydrodynamics; Lakes, Catastrophic failures; Glacial lake outburst flood; Maximum flow velocities; Mitigation measures; Mountain hazard; Sikkim Himalaya; South Lhonak; Two-dimensional hydrodynamic modeling, Floods
Department/Centre:	Division of Mechanical Sciences > Divecha Centre for Climate Change
Date Deposited:	26 Mar 2019 07:51
Last Modified:	25 Sep 2022 06:23
URI:	https://eprints.iisc.ac.in/id/eprint/61985

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