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

Ice Thickness and Bed Elevation of the Northern and Southern Patagonian Icefields

“…Over the next century, NPI and SPI are expected to increase their rapid contribution to sea level (Braithwaite & Raper, 2002;Gardner et al, 2013;Glasser et al, 2011;Levermann et al, 2013), enhanced hazards from glacial lake outburst floods (Anacona et al, 2015;Dussaillant et al, 2009;Loriaux & Casassa, 2013), and issues with freshwater resource management. From our product, the largest potential for sea level change exist for San Rafael and San Quintin in NPI, Jorge Montt, Pio XI, Occidental, O'Higgins, and possibly Upsala in SPI.…”

Modelling glacial lake outburst flood impacts in the Bolivian Andes

“…Numerous parameters (e.g. peak discharge, sediment load, channel roughness) can modify the flood inundation and flow behaviour of a simulated flood, leading to uncertainty in flood modelling and risk assessment (Anacona et al 2015;Wang et al 2015b;Kropáček et al 2015). Table 1 presents a summary of the modelling scenarios undertaken, together with the accompanying values for each model parameter (i.e.…”

“…Although simulations of drainage duration can be tuned to fit an observed hydrograph, hydrograph forecasting is difficult because nonlinear flood physics make drainage duration sensitive to the initial conditions (Ng and Björnsson 2003), which are usually uncertain. All three of our potentially dangerous glacial lakes are either bedrock-or moraine-dammed, so we made the assumption that flood discharge would increase linearly to a peak, after which it decreases linearly to 0 m 3 /s over a time span equal to that of the rising limb; in other words, hydrographs were assumed to be triangular in shape as has been applied in previous GLOF modelling studies (Anacona et al 2015;Kropáček et al 2015;Somos-Valenzuela et al 2015;Wang et al 2015b) (Fig. 2).…”

“…2). Some previous studies have considered that the higher the peak discharge, the longer the flood duration (Anacona et al 2015;Wang et al 2015b), whereas others assume a shorter flood duration for a higher peak discharge (Somos-Valenzuela et al 2015). We chose to use the latter option such that our worst-case pessimistic scenario has the highest peak discharge and shortest flood duration, and the optimistic scenario has the lowest peak discharge and longest flood duration.…”

“…Such models require very little input data and can be applied to many lakes, but serve as a first-order assessment that cannot go as far as to produce realistic flood maps. Other studies have focused on more detailed modelling approaches using HEC-RAS 1D (Bajracharya et al 2007;Dortch et al 2011;Klimeš et al 2014;Watson et al 2015), HEC-RAS 2D (Anacona et al 2015;Wang et al 2015a, b), FLO 2D (Petrakov et al 2012;Somos-Valenzuela et al 2015), and BASE-MENT (Worni et al 2012(Worni et al , 2013Somos-Valenzuela et al 2016), all of which require further data such as channel bed roughness, and the volume of water that could drain from the lake. These techniques are capable of generating inundation maps (area affected, runout distance, and depth of flow) that can be used to inform risk management and mitigation strategies.…”