Tragedy in Nepal: How do flash floods happen?
When flash floods sweep through the Himalayas, there is often little time to react. Scientists are working to understand the risks and improve early warning systems.
On Wednesday, a flash flood struck the border region between China and Nepal, washing away 20 kilometers of land in just 10 minutes, leaving devastation in its wake. Flash floods are a common occurrence in the Himalayas, with Niels Hovius, an expert on early warning systems, stating that they are more the norm than the exception.
The disaster began with a massive glacier collapse, a common trigger for flash floods in high mountain regions. The ice breakup generated a torrent of water and debris, traveling at speeds comparable to those of passenger cars on German highways. Although an earthquake was recorded at the time of the collapse, it was not a typical tectonic quake but rather the force of the falling glacier.
Flash floods can also be triggered by glacial lake outburst floods (GLOFs), but in this case, it was clear that was not the cause. Landslides can create deadly mudflows without glaciers or glacial lakes. The narrow valleys of the Himalayas exacerbate the situation, as water and debris cannot disperse, leading to heightened depth and speed.
Nepal faces challenges with few early warning systems and a high population density in vulnerable areas. Hovius suggests mobile phone push notifications as a potential solution. Additionally, he advocates for relocating communities to higher ground to mitigate future disasters, which are likely to become more frequent due to climate change.
Written by urgent.news from DW News's reporting — not their text. Machine-written — may contain errors; check the original before relying on it.
