Hazard from Himalayan Glacier Lake Outburst Floods
Hazard from Himalayan glacier lake outburst floods Georg Veha,1, Oliver Korupa,b, and Ariane Walza aInstitute of Environmental Science and Geography, University of Potsdam, 14476 Potsdam-Golm, Germany; and bInstitute of Geosciences, University of Potsdam, 14476 Potsdam-Golm, Germany Edited by Andrea Rinaldo, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland, and approved November 27, 2019 (received for review August 27, 2019) Sustained glacier melt in the Himalayas has gradually spawned (17). While the distribution and dynamics of moraine-dammed more than 5,000 glacier lakes that are dammed by potentially lakes have been mapped extensively in recent years (12, 18–21), unstable moraines. When such dams break, glacier lake outburst objectively appraising the current Himalayan GLOF hazard has floods (GLOFs) can cause catastrophic societal and geomorphic remained challenging. The high-alpine conditions limit detailed impacts. We present a robust probabilistic estimate of average fieldwork, leading researchers to extract proxies of hazard from GLOFs return periods in the Himalayan region, drawing on 5.4 increasingly detailed digital topographic data and satellite imagery. billion simulations. We find that the 100-y outburst flood has These data allow for readily measuring or estimating the geometry of +3.7 6 3 an average volume of 33.5 /−3.7 × 10 m (posterior mean and ice and moraine dams, the possibility of avalanches or landslides 95% highest density interval [HDI]) with a peak discharge of entering a lake, or the water volumes released by outbursts (9, 18, 20). +2,000 3 −1 15,600 /−1,800 m ·s . Our estimated GLOF hazard is tied to Ranking these diagnostics in GLOF hazard appraisals has mostly the rate of historic lake outbursts and the number of present lakes, relied on expert judgment (18, 22), because triggers and condi- which both are highest in the Eastern Himalayas.
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