Glacier floods

Glacier floods, also known as jökulhlaups (from the Icelandic), glacier outbursts, glacial lake outburst floods (GLOFs), aluviónes and debacles, refer to the sudden release of water from a glacier hydrological system or from glacial lakes impounded by moraine sediments and/or ice [1]. The biggest floods ever to have occurred on the Earth’s surface (reaching peak discharges up to 17-18 x 106 m3/s) were from glaciers and affected thermohaline circulation and caused widespread and intense landscape change both onshore and offshore [2]. Holocene and modern events may not have had such a significant global impact, but they have posed a hazard to communities living downstream, and to infrastructure and land in the flood path (peak discharges reaching up to ~ 0.1 x 106 m3/s) [1]. In the last decade alone, glacier floods have threatened communities in Peru, Bolivia, Nepal, India, Pakistan, Iceland, Greenland, New Zealand, Switzerland, Russia and North America (Figure 1), destroying hydro-electric installations, road and rail infrastructure, farmland, housing and, in some cases, causing loss of human life. This chapter aims to review current knowledge regarding glacier floods, building on recent subject-specific contributions on proglacial lakes [3], jökulhlaup mechanisms [4], [5], geomorphological impacts [6], and outburst floods [7]. It will bring together understanding of five components: 1. the processes leading to the development and outburst of glacial lakes, 2. the form that different types of floods take (i.e. their character and dynamics) and their geomorphic impact, 3. flood modelling and associated challenges, 4. hazard identification and assessment procedures, and 5. hazard management (i.e. phenomena prediction, lake remediation, reducing exposure). We will focus primarily on advances made over the previous decades and in doing so will highlight remaining knowledge gaps, suggesting where ongoing and future research may wish to focus.