title: Reconstruction of a glacial lake outburst flood (GLOF) in the Engaño Valley, Chilean Patagonia: Lessons for GLOF risk management.
abstract: Floods from moraine-dammed lake failures can have long standing effects not only on riverine landscapes but also on mountain communities due to the high intensity (i.e. great depth and high velocities) and damaging capacity of glacial lake outburst floods (GLOFs). GLOFs may increase in frequency as glaciers retreat and new lakes develop and there is an urgent need to better understand GLOF dynamics and the measures required to reduce their negative outcomes. In Patagonia at least 16 moraine-dammed lakes have failed in historic time, however, data about GLOF dynamics and impacts in this region are limited. We reconstruct a GLOF that affected a small village in Chilean Patagonia in March 1977, by semi structured interviews, interpretation of satellite images and 2D hydraulic modelling. This provides insight into the GLOF dynamics and the planning issues that led to socioeconomic consequences, which included village relocation. Modelling shows that the water released by the GLOF was in the order of 12-13 × 10(6)m(3) and the flood lasted for about 10h, reaching a maximum depth of ~1.5m in Bahía Murta Viejo, ~ 26 km from the failed lake. The lake had characteristics in common with failed lakes worldwide (e.g. the lake was in contact with a retreating glacier and was dammed by a narrow-steep moraine). The absence of land-use planning and the unawareness of the GLOF hazard contributed to the village flooding. The Río Engaño GLOF illustrates how small-scale and short-distance migration is a reasonable coping strategy in response to a natural hazard that may increase in frequency as atmospheric temperature rises and glaciers retreat.
authors.affiliation: School of Geography, Environment and Earth Sciences, Victoria University of Wellington, New Zealand.
authors.forename: Pablo Iribarren
authors.initials: PI
authors.lastname: Anacona
authors.affiliation: School of Geography, Environment and Earth Sciences, Victoria University of Wellington, New Zealand.
authors.forename: Andrew
authors.initials: A
authors.lastname: Mackintosh
authors.affiliation: School of Geography, Environment and Earth Sciences, Victoria University of Wellington, New Zealand.
authors.forename: Kevin
authors.initials: K
authors.lastname: Norton
keywords: Bahía Murta; GLOF; HEC-RAS modelling; Migration; Patagonia