Glacial lakes represent a threat for the populations of the Andes and numerous disastrous glacial lake outburst floods (GLOFs) occurred as a result of sudden dam failures or dam overtoppings triggered by landslides such as rock/ice avalanches into the lake. This paper investigates a landslide-triggered GLOF process chain that occurred on February 23, 2020, in the Cordillera Vilcabamba in the Peruvian Andes. An initial slide at the SW slope of Nevado Salkantay evolved into a rock/ice avalanche. The frontal part of this avalanche impacted the moraine-dammed Lake Salkantaycocha, triggering a displacement wave which overtopped and surficially eroded the dam. Dam overtopping resulted in a far-reaching GLOF causing fatalities and people missing in the valley downstream. We analyze the situations before and after the event as well as the dynamics of the upper portion of the GLOF process chain, based on field investigations, remotely sensed data, meteorological data and a computer simulation with a two-phase flow model. Comparison of pre- and post-event field photographs helped us to estimate the initial landslide volume of 1–2 million m³. Meteorological data suggest rainfall and/or melting/thawing processes as possible causes of the landslide. The simulation reveals that the landslide into the lake created a displacement wave of 27 m height. The GLOF peak discharge at the dam reached almost 10,000 m³/s. However, due to the high freeboard, less than 10% of the lake volume drained, and the lake level increased by 10–15 m, since the volume of landslide material deposited in the lake (roughly 1.3 million m³) was much larger than the volume of released water (57,000 m³, according to the simulation). The model results show a good fit with the observations, including the travel time to the uppermost village. The findings of this study serve as a contribution to the understanding of landslide-triggered GLOFs in changing high-mountain regions.

冰河湖泊对安第斯山脉的居民构成威胁，由于突然的水坝溃决或由于滑坡（例如岩石/冰雪崩进入湖中）引发的水坝超顶而发生了许多灾难性的冰河湖泊爆发洪水（GLOF）。本文研究了一个滑坡触发的GLOF过程链，该过程链发生在2020年2月23日，在秘鲁安第斯山脉的Cordillera Vilcabamba。Nevado Salkantay西南偏坡的最初滑坡演化为岩石/冰雪崩。雪崩的前部影响了冰m筑坝的Lake Salkantaycocha湖，引发了位移波，该波冲顶并侵蚀了大坝。大坝翻越导致了影响深远的GLOF，导致死亡和下游山谷中的人员丧生。我们基于现场调查，遥感数据，气象数据以及具有两相流模型的计算机模拟，分析了事件发生前后的情况以及GLOF过程链上部的动态。事前和事后现场照片的比较帮助我们估计了1-2百万m的初始滑坡量³。气象数据表明降雨和/或融化/融化过程是滑坡的可能原因。模拟表明，滑入湖中的滑坡产生了27 m高的位移波。大坝的GLOF峰值流量达到近10,000 m ³ / s。但是，由于干舷高，湖中排水量不足10％，湖水位增加了10–15 m，这是因为沉积在湖中的滑坡物质的体积（约130万m ³）远大于放水量（57,000 m ³，根据仿真）。模型结果显示与观测值非常吻合，包括到最上层村庄的旅行时间。这项研究的结果有助于了解在不断变化的高山地区滑坡触发的GLOF。