Kathmandu, Sept 19: The catastrophic flash floods occurred in Nepal took the scientists by surprise, prompting them to immediately launch discussions and conduct studies to ascertain best possible factors behind the devastation.
Media have given various names ranging from Himalayan tsunami to flash floods to the August 26 disaster, while Nepal government is learnt to be conducting a comprehensive study on it.
At a time when the scale and intensity of the August 26 floods demonstrated beyond the river’s wrath in our recent memories, exposing utter limitation in adaptation, a cohort of scientists and researchers has attributed human-induced climate change, climate variability and geological factors behind the catastrophe that struck Nepal from China-Nepal border of Rasuwa district that left a trail of devastation downwards.
The report released by the World Weather Attribution (WWA) on September 17 titled, ‘rapid warming in the Himalaya exacerbates geohazard cascades beyond adaptation limits’. It has been covered widely by the national and international media.
Written by 24 scientists and researchers and reviewed by four authors, the study report stated, “Warming and permafrost degradation likely weakened the source rock wall by increasing bedrock temperatures and thawing ice within fractures. Loss of ice bonding reduces fracture strength, while meltwater can increase water pressure and further destabilise pre-existing geological weaknesses. Thus, permafrost degradation may have acted as an additional climate-related factor preconditioning the slope for failure.”
Importantly, the researchers have also hinted at the 2015 Earthquake as a triggering factor when it comes to the destabilization of geological structure. In the report, the researchers, however, admitted that it was yet to be ascertained whether the 2015 Earthquake magnitude 7.8 had specific role in the present disaster.
The earthquake had caused a catastrophic rock–ice avalanche at Langtang Lirung with massive damage in the region. Since then, incidents of steady elevation and landslide activities were recorded on rise by the scientists through the monitoring, thereby indicating that the earthquake might have weakened the underlying rock mass over the long term, according to the report.
The document tries to elaborate how cascading effects/results unfolded once the rock-ice avalanche occurred. “As the ice, rock and debris moved rapidly down the mountain, friction and mechanical energy probably caused some of the glacier ice to melt, producing large amounts of meltwater. When the avalanche reached the valley floor, it also hit buried ice, which probably melted and added more water to the debris flood.”
The debris flood which was perhaps triggered by multiple sources of water ranging from melting glacier ice to the water stored beneath the glacier and in permafrost, ice and river water advanced the surge, the report explained.
It added that the accumulation of water, ice, rock and sediment made the debris floods further devastating.
Boost adaptation capacity
The study report has recognized Nepal’s early warning systems and adaptation measures in place to minimize impacts from ‘more conventional’ and riverine floods. However, the August 26 disaster was of radical nature in terms of its ‘magnitude, speed and complexity’, it argued.
“No existing early warning system could have provided sufficient lead time or prevented the scale of impacts observed in the worst-affected areas,” it mentioned, exposing the adaptation limits.
The study has underscored urgency of augmenting adaptation capacity in the wake of rapid warming in Himalaya which is further compounded with extreme and complex hazards.
They have suggested the urgency of speedy transition away from the use of fossil fuel and adherence to climate finance commitment to Himalaya and other high mountains so that future hazards could be reduced. The report warns of glacier retreat and permafrost degradation likely to continue even in absence of further rise in temperature, and pending impacts of past warming, for these are yet to come to light fully.
The researchers engaged in the study report are from Nepal, Pakistan, the UK, Ireland, Sweden, Denmark, Norway, the US, New Zealand and the Netherlands. They have the expertise in the topics ranging from glaciology to mountain hydrology, climate science, humanitarian aid, seismology and social science.
WWA comprises researchers from various institutions, including the Centre for Environmental Policy, Imperial College London, The Royal Netherlands Meteorological Institute, and the Red Cross Red Crescent Climate Centre.
