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| Figure 1: Headlines regarding the June 2013 flooding event (hover to show -- source) |
The flash floods in Uttarakhand in mid-June 2013...evidence of anthropogenic influence? Uttarakhand, north-west India, is home to some of the highest mountains in the world e.g. Nanda Devi (25,646 feet [7,817 metres]) and is drained by numerous rivers of the Ganges system (Encyclopaedia Britannica). It made the headlines around the globe this year (Figure 1) due to devastating flash floods, that affected the region in mid-June. Heavy pre-monsoon snowfall during March-May led to increased meltwater in June; Two unusually intense weather systems combined (BBC) to produce prolonged heavy rainfall in June, further enhancing snow melt, and raising river levels higher still (The Hindu). Water accumulated in a glacial lake which eventually was breached (GLOF), causing the flash flood and widespread devastation (BBC - Video 1; BBC - Video 2).
Flash floods, typically coinciding with the summer monsoon, are the most common weather-driven natural disaster in this area, causing more fatalities in Uttarakhand than anywhere else in India (Panda, 2010). Panda (2010) also notes that flash floods have enjoyed a long history in Uttarakhand. This begs the question - where does anthropogenic influence fit into this equation?
"Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia" (AR5 Summary For Policymakers). Goswami et al. (2006) project an increase in intense precipitation events in a warming climate. Additionally, the rate of glacial retreat (majority of the world's glaciers are in retreat) and snow cover reduction, has increased through time (AR5 Summary For Policymakers). Combined or in isolation, these will increase the risk of flash floods (Guardian).
The point at which an event becomes a disaster often highlights mankind as the culprit. As I alluded to in Land-use & the monsoon, space is at a premium in India where ~72% of the population are rural (World Bank) often living in 'at risk' areas. It is with 'high confidence' that settlement patterns e.g. mountain settlements, have influenced the observed trends in exposure and vulnerability to extreme events (SREX Summary Report). It is often inadequate land management, such as construction or deforestation, that both put people at risk and create antecedent conditions that exacerbate climate effects (SREX Summary Report).
It remains very difficult to attribute individual extreme events to anthropogenic influence, especially those localised events like flash floods driven by cloud bursting (SREX Report). Were the 2013 floods evidence of anthropogenic influence? Arguably yes. Furthermore, anthropogenic influence on other potential drivers of flash floods is apparent and as such, headlines such as these could become more frequent in the future.
Next up...effects of extreme precipitation...bring your umbrella
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