The catchments of Rishiganga and then Dhauliganga valleys in the Chamoli district of Uttarakhand were impacted by a catastrophic flood triggered due to a massive rockslide, caused by wedge failure on 7th February, 2021. It is estimated that the massive rockslide of ~ 23 million cubic meter volume containing base rock, deposited ice, and snow got detached from the northern slopes of the Trishul mountain range near Ronti Glacier and created a vertical fall of almost 1700 m before severely impacting the Ronti Gad valley located at 1.5 km downstream of Ronti Glacier snout. The huge detached mass of rock and ice (GLIMS ID: G079733E30381N) swiftly moved downstream through the glaciated valley entraining snow, debris, mud on its way, caused rapid fluidization, created massive water/slush waves, and washed away partially or completely the hydel power projects and bridges in its route. It is estimated that ~ 0.93 Peta Joules of potential energy led to the generation of a significant amount of kinetic and thermal energy, good enough to trigger above-mentioned processes. Post-event analysis of high-resolution satellite data shows flood water marks in the valley and on the rock outcrops reaching up to ~ 80–150 m height on the way to Raini Village. The mud and the slush produced through this process led to the formation of a dammed lake and temporarily blocked one of the tributaries of the Rishiganga joining from the northeast. This study provides an insight into the sequence of events as they unfolded, through multi-temporal satellite image analysis, aerial survey, seismological data in conjunction with various other geo-spatial and geo-visualization tools for unraveling the flood event that has happened on February 7, 2021. We also discuss the potential cause of rockslide and the process mechanism of this unique event, causing loss of lives and property besides widespread devastation.

在2021年2月7日，由于楔形破坏引起的巨大岩石滑坡引发的巨灾，影响了北阿坎德邦Chamoli地区的Rishiganga山谷和Dhauliganga山谷的集水区。据估计，约有2300万立方米的巨大岩石滑坡。包含基础岩石，沉积的冰和雪的体积从Ronti冰川附近的Trishul山脉的北坡脱离，并造成了将近1700 m的垂直下降，然后严重冲击了位于Ronti冰川口鼻下游1.5 km的Ronti Gad谷地。巨大的岩石和冰块（GLIMS ID：G079733E30381N）迅速向下游移动，穿过结冰的山谷，夹杂着雪，碎屑，泥土，引起快速流化，产生了巨大的水/雪崩波，并部分或全部冲走了海德电力公司在其路线上的工程和桥梁。据估计，约0.93皮塔焦耳的势能导致产生大量动能和热能，足以触发上述过程。高分辨率卫星数据的事后分析显示，在到达雷尼村的途中，山谷和岩石露头上的洪水痕迹高达80-150 m。通过此过程产生的泥浆和泥浆导致形成了一个堰塞湖，并暂时阻塞了Rishiganga的一个支流从东北方向进入的支流。通过多时相卫星图像分析，航测，