What is a Glacial Hazard?

Reynolds (1992) defines a glacial hazard as ‘any glacier or glacier-related feature or process that adversely affects human activities’. The most widely occurring glacial hazards result from:
– The generation of Glacial Lake Outburst Floods (GLOFs) due to the formation and subsequent failure of ice- and moraine-dammed lakes.

– The generation of Glacier Outbursts or Jökulhlaups through the rapid release of water under pressure from within or beneath a glacier.

– The triggering of ice, rock and snow avalanches due to the destabilization of mountain slopes, degradation of permafrost and the influence of meteorological and earthquake events.

Glacial hazards can also be brought about through volcanic activity. The eruption of ice-covered Volcanoes, for example can result in highly dangerous lahars, mud flows made up of pyroclastic material, rocky debris and snow/ice melt water.

Why are Glacial Hazards of importance?

Glacial Hazards pose a significant risk to downstream communities and can cause serious damage to river/riverside infrastructure. These socio-economic risks have increased as human activities have extended further into glacierised regions. In Peru alone, outburst floods from glacial sources have caused ~32,000 deaths in the 20th century, as well as destroying vital economic infrastructure, settlements and valuable arable land (Reynolds, 1992; Richardson & Reynolds, 2000a.). Whilst in the Nepal Himalaya, it has been estimated that the costs associated with the destruction of a mature single hydropower installation by an outburst flood could exceed USD 500 million (Richardson & Reynolds, 2000a.).

During the 20th and 21st centuries the development and threat of glacial hazards has increased considerably as a result of the widespread downwasting of glaciers globally. Triggered by atmospheric warming and changes in the levels of precipitation since the end of the Little Ice Age (~1850), glacial retreat and thinning has resulted in the increase in number and size of glacial lakes in mountainous regions (such as the Himalayas, the European Alps, and the Andes Cordillera), with increased ice meltwater production often pooling behind ice dams, weak lateral and terminal moraines left behind by retreating glacier fronts, and within over-deepened newly de-glaciated valley bottoms until, in some cases, being catastrophically released downstream (Dussaillant et al., 2010; Loriaux & Casassas, 2013). Additionally, the process of deglaciation has resulted in the destabilization of bedrock and drift-covered slopes (Holm et al., 2004), and the degradation of permafrost (Haeberli, 2013), in turn promoting rock falls and debris avalanches.

In line with global trends (Mernild et al., 2013), glaciers in the Chilean Andes have also been retreating and thinning considerably over recent decades. Recent monitoring studies performed for the central Chilean Andes have revealed glacier area losses of ~30% (~0.5% per year) between 1955 and 2014 (Malmros et al., in press), whilst a similar study performed for Northern Patagonia estimated area losses of ~25% (~1% per year) between 1985 and 2011 (Paul & Mölg, 2014). However, despite evidence that ice-dammed and moraine dammed lakes are now developing in Chile in response to glacier retreat, and recent studies identifying former GLOF sites, relatively little is known in regards to the extent of glacial hazards in Chile and their present and future risk to downstream populations and infrastructure (Iribarren Anacona et al., 2015).

**For references cited please see the Links and Publications page**