Study of temporal response (1976-2019) and associated mass movement event (during 2017) of Meru glacier, Bhagirathi valley, Garhwal Himalaya, India

Impact of climate change on glaciers brings the favorable conditions of lakes formation within glacier moraines. These lakes may produce outburst floods and transport the huge amount of debris (debris flow) in downstream settlements. The present study addresses the current knowledge on mass movement activity occurred in the Gangotri glacier area, Garhwal Himalaya Uttarakhand. Temporal response (terminus retreat and frontal area loss) of Meru glacier during 1976-2019 using the images of Landsat (MSS, 1976; TM, 1990, 2011; ETM+, 2001; OLI, 2019) and event of intense mass movement occurred along Meru glacier during 2017 is assessed. Our estimations clearly reveals that the Meru glacier is retreating continuously since 1976 with inconsistent rate. Considering the time span 1976-1990, 1990-2001, 2001-2011, 2011-2019 the terminus receded with 12.42 m y(-1), 7.72 m y(-1), 6.00 m y(-1), 11.50 m y(-1) and vacated the frontal area at the rate of 2330.70 m(2) y(-1), 2185.88 m(2) y(-1), 1425.18 m(2) y(-1), 1452.66 m(2) y(-1) respectively. Field observations and high resolution imagery of LISS IV suggest that the lower area of Meru glacier experienced the event of intense mass movement in July, 2017. This event breached the continuity of left morainic wall of Bhagirathi valley. This mass movement event influenced the initial course of Bhagirathi River (similar to 1559 m length) and also modified the morphology of the Gaumukh region. The precipitation data from Indian Meteorological Department (IMD) and satellite images of different years suggest that the multiple factors such as intense precipitation, large amount of sediment transport from the upper reaches to lower area, slope failure, collapse of frontal part of Meru glacier were the main causative factors for this event.