A glacial lake outburst floods hazard assessment in the Patagonian Andes combining inventory data and case-studies.

We present a glacial-related lake inventory for a region spanning 41.5° - 47° S in Patagonian Andes, where information on past glacier lake outburst floods (GLOF's) has hitherto remained significantly underreported. Analyzing remotely sensed images, we obtained data on 702 glacial-related lakes. Through detailed geomorphic assessments and manual supervision, we revised current inventories and added 35 GLOFs triggered from moraine/bedrock dammed lakes failures. The regional GLOF inventory presented contains information on 71 historical failures of moraine/bedrock dammed glacial lakes. From this database we analyzed outburst timing and managed to constrain 37 events occurrences within a period of 1 year. Around 40 % of them have occurred since the early 2000's, most of them originating from lakes probably formed as a delayed response to the glacial retreat imposed by the end of the Little Ice Age. On the other hand, we analyzed meteorological conditions for a sub-set of 10 events constrained within a 10-days period, finding a strong link between atmospheric rivers, cut-off lows impacting the southern Andes, and GLOFs. Only one case is likely to have been triggered by a Mw 4.9 earthquake. Based on topographic potential for avalanching, we estimated GLOF hazard potential, recognizing at least 3 subregions with high hazard, which moreover can be highly susceptible to climate conditions that regionally affect GLOF occurrence.

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