Review Coupling glacial lake impact, dam breach, and flood processes: A modeling perspective Raphael Worni a,b , Christian Huggel a,d , John J. Clague c , Yvonne Schaub d , Markus Stoffel a,b, ⁎ a Institute for Environmental Sciences, University of Geneva, Switzerland b Institute of Geological Sciences, University of Bern, Switzerland c Department of Geography, University of Zurich, Switzerland d Department of Earth Sciences, Simon Fraser University, British Columbia, Canada abstract article info Article history: Received 24 May 2014 Received in revised form 25 June 2014 Accepted 26 June 2014 Available online 24 July 2014 Keywords: Glacial lake outburst flood (GLOF) Process chain Dynamic modeling Natural hazard BASEMENT FLO-2D RAMMS Glacial lake outburst floods (GLOFs) are highly mobile mixtures of water and sediment that occur suddenly and are capable of traveling tens to hundreds of kilometers with peak discharges and volumes several orders of magnitude larger than those of normal floods. They travel along existing river channels, in some instances into populated down- stream regions, and thus pose a risk to people and infrastructure. Many recent events involve process chains, such as mass movements impacting glacial lakes and triggering dam breaches with subsequent outburst floods. A concern is that effects of climate change and associated increased instability of high mountain slopes may exacerbate such pro- cess chains and associated extreme flows. Modeling tools can be used to assess the hazard of potential future GLOFs, and process modeling can provide insights into complex processes that are difficult to observe in nature. A number of numerical models have been developed and applied to simulate different types of extreme flows, but such model- ing faces challenges stemming from a lack of process understanding and difficulties in measuring extreme flows for calibration purposes. Here we review the state of knowledge of key aspects of modeling GLOFs, with a focus on pro- cess cascades. Analysis and simulation of the onset, propagation, and potential impact of GLOFs are based on illus- trative case studies. Numerical models are presently available for simulating impact waves in lakes, dam failures, and flow propagation but have been used only to a limited extent for integrated simulations of process cascades. We present a spectrum of case studies from Patagonia, the European Alps, central Asia, and theHimalayas in which we simulate single processes and process chains of past and potential future events. We conclude that process understanding and process chain modeling need to be strengthened and that research efforts should focus on a more integrative treatment of processes in numerical models. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Glacier thinning and retreat over the past century has led to the formation and growth of lakes at the margins of glaciers and moraines in all high mountain regions of the world (IPCC, 2012). Sudden draining of these lakes has caused disasters in the Andes (Lliboutry et al., 1977; Reynolds et al., 1998; Carey, 2005; Hegglin and Huggel, 2008), Caucasus and central Asia (Aizen et al., 1997; Narama et al., 2006), the Himalayas (Vuichard and Zimmermann, 1987; Richardson and Reynolds, 2000a; Xin et al., 2008), Iceland (Björnsson, 2002; Russell et al., 2006), North America (Post and Mayo, 1971; Mathews and Clague, 1993; Clague and Evans, 2000; Geertsema and Clague, 2005; Kershaw et al., 2005), and the European Alps (Haeberli, 1983; Haeberli et al., 2001). The formation of new glacial lakes in a warming climate is paralleled by slope destabilization in many regions (Stoffel and Huggel, 2012). Debuttressing of rock slopes adjacent to downwasting glaciers is an important cause of many alpine rock slope failures (Evans and Clague, 1994; Ballantyne, 2002; Geertsema et al., 2006) and has recently resulted in a number of large rock falls, rockslides, and ice avalanches (Fischer et al., 2010; Huggel et al., 2012b). Evidence is also increasing that perma- frost thaw and related processes have destabilized alpine slopes and caused failures in unprecedented numbers in recent decades (Gruber and Haeberli, 2007; Krautblatter et al., 2012). An increase in high mountain rock slope failures has recently been detected at local and regional scales in the Alps (Huggel et al., 2012a). The coincident development of new and expanding glacial lakes and the decreasing stability of steep bedrock slopes increase the possibility that landslides and ice avalanches will impact lakes, potentially triggering very large downstream floods. Many lake outburst floods in the recent past have resulted from such linked processes (Clague and Evans, 2000; Kershaw et al., 2005; Carey et al., 2012). Geomorphology 224 (2014) 161–176 ⁎ Corresponding author at: Dendrolab.ch, Institute of Geological Sciences, University of Bern, Baltzerstrasse 1+3, CH-3012 Bern, Switzerland. Tel.: +41 31 631 87 73; fax: +41 31 631 48 43. E-mail addresses: markus.stoffel@dendrolab.ch (R. Worni), christian.huggel@geo.uzh.ch (C. Huggel), jclague@sfu.ca (J.J. Clague), yvonne.schaub@geo.uzh.ch (Y. Schaub), markus.stoffel@dendrolab.ch (M. Stoffel). http://dx.doi.org/10.1016/j.geomorph.2014.06.031 0169-555X/© 2014 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Geomorphology journal homepage: www.elsevier.com/locate/geomorph