On August 14 th 2015 a large debris flow initiated by the occurrence of two slope failures at the front of the Lou rock glacier flooded part of the town of Lanslevillard, France. The present study aims to understand the meteorological and geomorphological context that led to these failures. Investigations were conducted by combining meteorological data, surface movements, and geophysical transects. The analysis indicates that the Lou rock glacier is directly connected to an active torrential channel and has a natural predisposition to frontal failure due to the steepness of its front. The slope failures were triggered after a heat wave followed by a three‐week period of almost continuous rainfall. Water flowing on top of the permafrost table was observed in the two head scarps, suggesting that regressive erosion consecutive to this concentrated subsurface water flow triggered the failures. For one of the slides, traces of previous failures were observable on historical aerial imagery dating back to the 1950's, while the second slide corresponded to a novel event and developed on the frontal slope of a fast‐moving and destabilized rock glacier lobe. We also discuss the increase in local predisposition to failure related to the remarkable morphological modifications such as frontal advance and development of surface cracks associated with the lobe destabilization.

中文翻译：

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法国阿尔卑斯山娄岩冰川前缘边坡失稳调查

2015 年 8 月 14 日，由 Lou 岩石冰川前部发生的两次斜坡崩塌引发的大型泥石流淹没了法国 Lanslevillard 镇的部分地区。本研究旨在了解导致这些故障的气象和地貌背景。调查是通过结合气象数据、地表运动和地球物理断面进行的。分析表明，娄岩冰川直接连接到一个活跃的洪流通道，并且由于其锋面的陡峭而具有锋面破坏的自然倾向。斜坡失稳是在热浪之后引发的，随后是三周的几乎连续降雨。在两个头部陡坡中观察到在永久冻土台顶部流动的水，这表明与这种集中的地下水流连续的回归侵蚀引发了故障。对于其中一张幻灯片，可以在可追溯到 1950 年代的历史航拍图像上观察到以前的失败痕迹，而第二张幻灯片对应于一个新事件，并在快速移动且不稳定的岩石冰川叶的正面斜坡上形成。我们还讨论了与显着的形态修改相关的局部故障倾向的增加，例如与叶不稳定相关的正面推进和表面裂纹的发展。而第二张幻灯片对应于一个新事件，并在快速移动和不稳定的岩石冰川叶的正面斜坡上发展。我们还讨论了与显着形态变化相关的局部故障倾向的增加，例如与叶不稳定相关的正面推进和表面裂纹的发展。而第二张幻灯片对应于一个新事件，并在快速移动和不稳定的岩石冰川叶的正面斜坡上发展。我们还讨论了与显着形态变化相关的局部故障倾向的增加，例如与叶不稳定相关的正面推进和表面裂纹的发展。