Hazardous processes and events from glacier and permafrost areas: lessons from the Chilean and Argentinean Andes

Abstract

Glacier and permafrost hazards such as glacial-lake outburst floods and rock-ice avalanches cause significant socioeconomic damages worldwide, and these processes may increase in frequency and magnitude if the atmospheric temperature rises. In the extratropical Andes nearly 200 human deaths were linked to these processes during the twentieth century. We analysed bibliographical sources and satellite images to document the glacier and permafrost dynamics that have caused socio-economic damages in this region in historic time (including glacial lake outburst floods, ice and rock-ice avalanches and lahars) to unravel their causes and geomorphological impacts. In the extratropical Andes, at least 15 ice-dammed lakes and 16 moraine-dammed lakes have failed since the eighteenth century, causing dozens of floods. Some floods rank amongst the largest events ever recorded (5000 × 10 6 m 3 and 229 × 10 6 m 3 , respectively). Outburst flood frequency has increased in the last three decades, partially as a consequence of long-term (decades to centuries) climatic changes, glaciers shrinkage, and lake growth. Short-term (days to weeks) meteorological conditions (i.e. intense and/or prolonged rainfall and high temperature that increased meltwater production) have also triggered outburst floods and mass movements. Enormous mass failures of glaciers and permafrost (> 10 × 10 6 m 3 ) have impacted lakes, glaciers, and snow-covered valleys, initiating chain reactions that have ultimately resulted in lake tsunamis and far-reaching (> 50 km) flows. The eruption of ice-covered volcanoes has also caused dozens of damaging lahars with volumes up to 45 × 10 6 m 3 . Despite the importance of these events, basic information about their occurrence (e.g. date, causes, and geomorphological impact), which is well established in other mountain ranges, is absent in the extratropical Andes. A better knowledge of the processes involved can help to forecast and mitigate these events.

Reconstruction of a glacial lake outburst flood (GLOF) in the Engaño Valley, Chilean Patagonia: Lessons for GLOF risk management

“…This tendency has been observed for example in the Himalayas (Gardelle et al, 2011), tropical Andes (Ames, 1998) and Patagonia (Loriaux and Casassa, 2013). In Patagonia, at least 16 moraine-dammed lakes have failed in historic time (Iribarren Anacona et al, 2015) and one of these events is one of the largest GLOFs, in terms of flood volume, reported worldwide (Hauser, 2000;Clague and Evans., 2000). However, GLOFs in Patagonia have affected mostly uninhabited valleys and thus have been underreported.…”

Moraine-dammed lake failures in Patagonia and assessment of outburst susceptibility in the Baker Basin

“…the end of the path) when it reaches a predetermined ending condition generally set as the angle of reach (i.e. the angle of the line connecting the starting and the ending zone of a mass movement; Hsu, 1975) (see Huggel et al, 2003 and for model details).…”

“…A fourth ice-dammed lake (Laguna Bonita) emptied at least two times between 2002 and 2008. However, glacier retreat since the last outburst now impedes the lake refilling (Iribarren Anacona et al, 2014). Of the 386 moraine-dammed lakes at least seven have produced outburst floods.…”

“…Since the beginning of the 20th century, at least 16 moraine-dammed lakes have failed in Patagonia (Iribarren Anacona et al, 2014). Seven of these lakes are located in the Baker Basin where major hydroelectric generation plants are planned.…”

“…One of these GLOFs (Laguna del Cerro Largo) is probably the largest outburst of a moraine-dammed lake (in terms of water volume released, 229 × 10 6 m 3 ) reported worldwide (Hauser, 1993;Clague and Evans, 2000). In the Baker Basin GLOFs have destroyed houses, forced the relocation of a village and have damaged inhabitant's livelihoods (Iribarren Anacona et al, 2014). Furthermore, a flood wave with GLOF characteristics killed three people boating in the Baker River in January 1977 (El Diario de Aysén, 1977a, b).…”