At this point in society’s understanding of climate change, there is a general awareness that the effects of a warming world are bringing about the melting and disappearance of our alpine (mountainous) and arctic glaciers. But what happens to all that water?
Meltwater is dispersed into the glacier’s surrounding area which, depending on the geography and location, often lead to river or lake formations on land. Glacial rivers can eb and flow depending on the drainage and season, however lakes tend to withhold their volume and grow over time. Depending on how these lakes are held together can lead to a stable and static water body or can quickly become a devastating force called a glacial lake outburst flood.
What is a GLOF and how do they form?
A glacial lake outburst flood (GLOF) is a sudden release of meltwater lake formed by the glacier, which was initially held by an ice dam or a moraine (accumulation of debris). As glaciers melt, these barriers are only as strong as their structure allows them to be. The failure of these dams and moraines can be tied to the integrity of those structures and also the nature of the triggering mechanism. Some of these triggers can be associated with waves resulting from calving ice chunks, rapid inputs of meltwater, heavy rainfall or snowfall events and disruption caused by earthquake activity. Once these barriers break, there’s no stopping what’s held behind those walls.
What are the costs associated?
When these dams or moraines burst, there is often little to no warning which is an attributing factor in the costs of these events. The flood water, carrying ice and debris can travel more than 100km downstream and can be comparable to monsoonal river discharges depending on the size of the flood. This is an important comparison, especially as in the Himalayan region and surrounding mountain ranges, monsoonal floods are considered among the top destructive natural hazards. In an instant, communities and infrastructure downstream become at risk for human life and livestock losses as well as damages to roads, buildings and hydropower facilities.
According to records in the 20th century, impacts from GLOFs have been responsible for approximately 32,000 deaths. With expectations that flood frequencies will increase as the 21st century continues, millions of lives are at risk. One study completed by Georg Veh et al. 2020 [HK1] quantified that just in the areas of the lower Indus, Ganges and Brahmaputra rivers, an estimated 220 million people are at risk of flood impacts. With the quantity and size of glacial lakes increases as global mean temperatures continue to rise, we could see more people at risk as time goes on.
In one recorded instance dubbed the Ci-Ren-Ma-Co (Zhangzangbo) outburst of 1981, approximately $3 Million USD in damages was documented with impacts on the Nepal-China Friendship Bridge, Arniko Highway, Sunkoshi hydropower dam, transportation services among other personal and structural losses. It is important to note that depending on the impact of the flood, these costs have been modelled up to hundreds of millions in total damages.
What can we do?
Now, as GLOF’s are unpredictable beasts, it can be difficult to fully implement mitigation approaches to minimise or eliminate the effects associated with these potential events. However, some communities have put in place efforts to manually drain these bodies of water whereas others have reinforced artificial dams with stone and concrete.
Luckily in most cases, when a glacial lake has burst through its moraine walls, the damming mechanism is destroyed and the capacity for storing glacial meltwater is lost. This means that these events are often one-time events so their ability for future destruction is decreased. We cannot forget, however, that as the earth continues to warm there will be an increase in glacial melt with an associated increase in glacial lake formations and associated GLOF events.
You can also take responsibility for your own environmental impact on the earth by calculating your carbon footprint, reducing your energy usage and offsetting your emissions. Click the button below to calculate your carbon footprint with the MyCarbon carbon footprint calculator, it's free with no sign up required!
And with that, I’ll wrap up this week’s post. Tune in two weeks from now for another thrilling read, this time on the Derechos & Flooding in Midwestern USA!
[HK1]Veh, G., Korup, O., & Walz, A. (2020). Hazard from Himalayan glacier lake outburst floods. Proceedings of the National Academy of Sciences, 117(2), 907-912.
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